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29.5: Birds - Biology

29.5: Birds - Biology



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Skills to Develop

  • Describe the evolutionary history of birds
  • Describe the derived characteristics in birds that facilitate flight

The most obvious characteristic that sets birds apart from other modern vertebrates is the presence of feathers, which are modified scales. While vertebrates like bats fly without feathers, birds rely on feathers and wings, along with other modifications of body structure and physiology, for flight.

Characteristics of Birds

Birds are endothermic, and because they fly, they require large amounts of energy, necessitating a high metabolic rate. Like mammals, which are also endothermic, birds have an insulating covering that keeps heat in the body: feathers. Specialized feathers called down feathers are especially insulating, trapping air in spaces between each feather to decrease the rate of heat loss. Certain parts of a bird’s body are covered in down feathers, and the base of other feathers have a downy portion, whereas newly hatched birds are covered in down.

Feathers not only act as insulation but also allow for flight, enabling the lift and thrust necessary to become airborne. The feathers on a wing are flexible, so the collective feathers move and separate as air moves through them, reducing the drag on the wing. Flight feathers are asymmetrical, which affects airflow over them and provides some of the lifting and thrusting force required for flight (Figure (PageIndex{1})). Two types of flight feathers are found on the wings, primary feathers and secondary feathers. Primary feathers are located at the tip of the wing and provide thrust. Secondary feathers are located closer to the body, attach to the forearm portion of the wing and provide lift. Contour feathers are the feathers found on the body, and they help reduce drag produced by wind resistance during flight. They create a smooth, aerodynamic surface so that air moves smoothly over the bird’s body, allowing for efficient flight.

Flapping of the entire wing occurs primarily through the actions of the chest muscles, the pectoralis and the supracoracoideus. These muscles are highly developed in birds and account for a higher percentage of body mass than in most mammals. These attach to a blade-shaped keel, like that of a boat, located on the sternum. The sternum of birds is larger than that of other vertebrates, which accommodates the large muscles required to generate enough upward force to generate lift with the flapping of the wings. Another skeletal modification found in most birds is the fusion of the two clavicles (collarbones), forming the furcula or wishbone. The furcula is flexible enough to bend and provide support to the shoulder girdle during flapping.

An important requirement of flight is a low body weight. As body weight increases, the muscle output required for flying increases. The largest living bird is the ostrich, and while it is much smaller than the largest mammals, it is flightless. For birds that do fly, reduction in body weight makes flight easier. Several modifications are found in birds to reduce body weight, including pneumatization of bones. Pneumatic bones are bones that are hollow, rather than filled with tissue (Figure (PageIndex{2})). They contain air spaces that are sometimes connected to air sacs, and they have struts of bone to provide structural reinforcement. Pneumatic bones are not found in all birds, and they are more extensive in large birds than in small birds. Not all bones of the skeleton are pneumatic, although the skulls of almost all birds are.

Other modifications that reduce weight include the lack of a urinary bladder. Birds possess a cloaca, a structure that allows water to be reabsorbed from waste back into the bloodstream. Uric acid is not expelled as a liquid but is concentrated into urate salts, which are expelled along with fecal matter. In this way, water is not held in the urinary bladder, which would increase body weight. Most bird species only possess one ovary rather than two, further reducing body mass.

The air sacs that extend into bones to form pneumatic bones also join with the lungs and function in respiration. Unlike mammalian lungs in which air flows in two directions, as it is breathed in and out, airflow through bird lungs travels in one direction (Figure (PageIndex{3})). Air sacs allow for this unidirectional airflow, which also creates a cross-current exchange system with the blood. In a cross-current or counter-current system, the air flows in one direction and the blood flows in the opposite direction, creating a very efficient means of gas exchange.

Evolution of Birds

The evolutionary history of birds is still somewhat unclear. Due to the fragility of bird bones, they do not fossilize as well as other vertebrates. Birds are diapsids, meaning they have two fenestrations or openings in their skulls. Birds belong to a group of diapsids called the archosaurs, which also includes crocodiles and dinosaurs. It is commonly accepted that birds evolved from dinosaurs.

Dinosaurs (including birds) are further subdivided into two groups, the Saurischia (“lizard like”) and the Ornithischia (“bird like”). Despite the names of these groups, it was not the bird-like dinosaurs that gave rise to modern birds. Rather, Saurischia diverged into two groups: One included the long-necked herbivorous dinosaurs, such as Apatosaurus. The second group, bipedal predators called theropods, includes birds. This course of evolution is suggested by similarities between theropod fossils and birds, specifically in the structure of the hip and wrist bones, as well as the presence of the wishbone, formed by the fusing of the clavicles.

One important fossil of an animal intermediate to dinosaurs and birds is Archaeopteryx, which is from the Jurassic period (Figure (PageIndex{4})). Archaeopteryx is important in establishing the relationship between birds and dinosaurs, because it is an intermediate fossil, meaning it has characteristics of both dinosaurs and birds. Some scientists propose classifying it as a bird, but others prefer to classify it as a dinosaur. The fossilized skeleton of Archaeopteryx looks like that of a dinosaur, and it had teeth whereas birds do not, but it also had feathers modified for flight, a trait associated only with birds among modern animals. Fossils of older feathered dinosaurs exist, but the feathers do not have the characteristics of flight feathers.

It is still unclear exactly how flight evolved in birds. Two main theories exist, the arboreal (“tree”) hypothesis and the terrestrial (“land”) hypothesis. The arboreal hypothesis posits that tree-dwelling precursors to modern birds jumped from branch to branch using their feathers for gliding before becoming fully capable of flapping flight. In contrast to this, the terrestrial hypothesis holds that running was the stimulus for flight, as wings could be used to improve running and then became used for flapping flight. Like the question of how flight evolved, the question of how endothermy evolved in birds still is unanswered. Feathers provide insulation, but this is only beneficial if body heat is being produced internally. Similarly, internal heat production is only viable if insulation is present to retain that heat. It has been suggested that one or the other—feathers or endothermy—evolved in response to some other selective pressure.

During the Cretaceous period, a group known as the Enantiornithes was the dominant bird type (Figure (PageIndex{5})). Enantiornithes means “opposite birds,” which refers to the fact that certain bones of the feet are joined differently than the way the bones are joined in modern birds. These birds formed an evolutionary line separate from modern birds, and they did not survive past the Cretaceous. Along with the Enantiornithes, Ornithurae birds (the evolutionary line that includes modern birds) were also present in the Cretaceous. After the extinction of Enantiornithes, modern birds became the dominant bird, with a large radiation occurring during the Cenozoic Era. Referred to as Neornithes (“new birds”), modern birds are now classified into two groups, the Paleognathae (“old jaw”) or ratites, a group of flightless birds including ostriches, emus, rheas, and kiwis, and the Neognathae (“new jaw”), which includes all other birds.

Career Connection: Veterinarian

Veterinarians treat diseases, disorders, and injuries in animals, primarily vertebrates. They treat pets, livestock, and animals in zoos and laboratories. Veterinarians usually treat dogs and cats, but also treat birds, reptiles, rabbits, and other animals that are kept as pets. Veterinarians that work with farms and ranches treat pigs, goats, cows, sheep, and horses.

Veterinarians are required to complete a degree in veterinary medicine, which includes taking courses in animal physiology, anatomy, microbiology, and pathology, among many other courses. The physiology and biochemistry of different vertebrate species differ greatly.

Veterinarians are also trained to perform surgery on many different vertebrate species, which requires an understanding of the vastly different anatomies of various species. For example, the stomach of ruminants like cows has four compartments versus one compartment for non-ruminants. Birds also have unique anatomical adaptations that allow for flight.

Some veterinarians conduct research in academic settings, broadening our knowledge of animals and medical science. One area of research involves understanding the transmission of animal diseases to humans, called zoonotic diseases. For example, one area of great concern is the transmission of the avian flu virus to humans. One type of avian flu virus, H5N1, is a highly pathogenic strain that has been spreading in birds in Asia, Europe, Africa, and the Middle East. Although the virus does not cross over easily to humans, there have been cases of bird-to-human transmission. More research is needed to understand how this virus can cross the species barrier and how its spread can be prevented.

Birds are endothermic, meaning they produce their own body heat and regulate their internal temperature independently of the external temperature. Feathers not only act as insulation but also allow for flight, providing lift with secondary feathers and thrust with primary feathers. Pneumatic bones are bones that are hollow rather than filled with tissue, containing air spaces that are sometimes connected to air sacs. Airflow through bird lungs travels in one direction, creating a cross-current exchange with the blood. Birds are diapsids and belong to a group called the archosaurs. Birds are thought to have evolved from theropod dinosaurs. The oldest known fossil of a bird is that of Archaeopteryx, which is from the Jurassic period. Modern birds are now classified into two groups, Paleognathae and Neognathae.

Review Questions

A bird or feathered dinosaur is ________.

  1. Neornithes
  2. Archaeopteryx
  3. Enantiornithes
  4. Paleognathae

B

Which of the following feather types helps to reduce drag produced by wind resistance during flight?

  1. flight feathers
  2. primary feathers
  3. secondary feathers
  4. contour feathers

D

Free Response

Explain why birds are thought to have evolved from theropod dinosaurs.

This is suggested by similarities observed between theropod fossils and birds, specifically in the design of the hip and wrist bones, as well as the presence of a furcula, or wishbone, formed by the fusing of the clavicles.

Describe three skeletal adaptations that allow for flight in birds.

The sternum of birds is larger than that of other vertebrates, which accommodates the force required for flapping. Another skeletal modification is the fusion of the clavicles, forming the furcula or wishbone. The furcula is flexible enough to bend during flapping and provides support to the shoulder girdle during flapping. Birds also have pneumatic bones that are hollow rather than filled with tissue.

Glossary

Archaeopteryx
transition species from dinosaur to bird from the Jurassic period
contour feather
feather that creates an aerodynamic surface for efficient flight
down feather
feather specialized for insulation
Enantiornithes
dominant bird group during the Cretaceous period
flight feather
feather specialized for flight
furcula
wishbone formed by the fusing of the clavicles
Neognathae
birds other than the Paleognathae
Neornithes
modern birds
Paleognathae
ratites; flightless birds, including ostriches and emus
pneumatic bone
air-filled bone
primary feather
feather located at the tip of the wing that provides thrust
secondary feather
feather located at the base of the wing that provides lift
theropod
dinosaur group ancestral to birds

Prevalence and phylogeny of coronaviruses in wild birds from the Bering Strait area (Beringia)

Coronaviruses (CoVs) can cause mild to severe disease in humans and animals, their host range and environmental spread seem to have been largely underestimated, and they are currently being investigated for their potential medical relevance. Infectious bronchitis virus (IBV) belongs to gamma-coronaviruses and causes a costly respiratory viral disease in chickens. The role of wild birds in the epidemiology of IBV is poorly understood. In the present study, we examined 1,002 cloacal and faecal samples collected from 26 wild bird species in the Beringia area for the presence of CoVs, and then we performed statistical and phylogenetic analyses. We detected diverse CoVs by RT-PCR in wild birds in the Beringia area. Sequence analysis showed that the detected viruses are gamma-coronaviruses related to IBV. These findings suggest that wild birds are able to carry gamma-coronaviruses asymptomatically. We concluded that CoVs are widespread among wild birds in Beringia, and their geographic spread and frequency is higher than previously realised. Thus, Avian CoV can be efficiently disseminated over large distances and could be a genetic reservoir for future emerging pathogenic CoVs. Considering the great animal health and economic impact of IBV as well as the recent emergence of novel coronaviruses such as SARS-coronavirus, it is important to investigate the role of wildlife reservoirs in CoV infection biology and epidemiology.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1. Neighbour-joining tree of CoVs based…

Figure 1. Neighbour-joining tree of CoVs based on a 560-nt fragment (excluding primer sequences) of…

Figure 2. Map of Beringia showing locations…

Figure 2. Map of Beringia showing locations where wild bird samples analysed in this study…


Finding the Best Binoculars for Birding

Selecting binoculars is a lot like tasting wines. It takes most people years of experience to be able to notice subtle differences in quality and articulate preferences using just the right lingo. Personal preference plays a large role in picking favorites. You could sip one of the world’s finest chardonnays and dislike the smooth, buttery finish derived from the oak barrels. In the same way, you might turn your nose up at the open-bridge design of a pair of top-of-the-line Swarovskis, a feature adored by many.

In optics as in wines, there is a large spectrum of prices, subtle differences are many, and the process of selecting one or describing why you like a particular one can be intimidating. Wines and binoculars follow the same general rule: you get what you pay for, and purchasing the best you can afford almost always pays off. That said, you don’t need to be a master sommelier or professional optics rep to make a good decision. In whatever price range you choose, when all is said and done, we hope you will feel that you’ve gotten good value for your money.

As you select new binoculars, we encourage you to try several pairs on your own and figure out what you like, if you haven’t already done so. In this review we showcase some of the favorites based on ratings by our 60 “tasters”—including optics aficionados and casual and hardcore birders—as well as our own personal experience. Rather than provide a comprehensive list of the specifications and ratings for all of the binocular models we tested, the optics presented here are our Top Picks in each price category—those we feel are the best value, optically solid, and ergonomically comfortable. For the full report, visit our website at www.birds.cornell.edu/binos. We aim to help you find binoculars that will fit you and your birding style.

A disclaimer: testing binoculars follows another important rule of wine tasting. After tasting a flight of wines, they all start to taste the same. We found this to be true after testing a lineup of binoculars. After a while, as your eyes get tired, it’s harder to discern differences.

WHAT’S NEW?

Since our last full binocular review in 2005, the sheer number of binocular models has steadily increased, and fortunately so has the overall quality of models in all price ranges. Although the price tag for the top models has crept toward the $3,000 mark, optics-makers have also improved optical performance with new types of glass, new lens coatings, and new ergonomic features that reduce weight and bulk. A relatively compact and fully waterproof roof-prism design, with high-quality, close-focusing optics, adjustable twisting eyecups, and excellent eye-relief are all now standard for models in nearly every price range.

Readers will recognize many familiar binocular brands among our Top Picks, but some new names—Alpen, Atlas, Opticron (popular in the United Kingdom), Vixen, and Zen-Ray—now vie for birders’ attention. Competition for brand loyalty among a growing and ever-more-discerning birder market has also fueled a trend toward greater corporate attention to service, sustainability, and support for birding and conservation programs. Along with fine optics, birders can now expect lifetime service warranties, superior customer support, and company presence at birding festivals and on conservation websites.

More Resources

Save and print the following resources via our downloads page:

  • Full PDF of the Living Bird review
  • Top Picks table, with comments and specifications for 27 models
  • Full review spreadsheet, with data for all 102 binocular models

THINGS TO CONSIDER

With all that’s new and exciting in the world of binoculars, the same basic principles still apply for choosing the right binoculars for your birding needs. The daunting task of selecting from among the dozens of binocular models available can be made simpler by considering the following options.

Price: In general, we recommend spending as much as you can afford on binoculars, because a higher price usually indicates (with some exceptions) higher quality and durability. We were excited, however, by the excellent choices in the lower and midpriced categories. We’ve selected our Top Picks in each of five price ranges. Although many birders always opt for the latest top-of-the line binoculars, several models in the “New Midrange” are so nice, they really make us wonder whether the extra $1,000 to $2,000 might be better spent on a trip to an exotic birding destination or to help support your favorite bird organization. For birders on a tight budget or educators looking to buy several binoculars, we were pleased to see a few remarkably good models for under $200—although how well these hold up under rugged or wet field conditions remains to be seen. Please note: the prices we list are the manufacturer’s suggested list prices you can often find lower prices than these online or at discount retailers.

Magnification: Nearly all of the models we tested come in a choice of 10x or 8x (or sometimes 7x) magnification, and because they are usually so similar in design and overall quality, we present review data mostly for the 8x models. Selecting 8x or 10x is highly subjective, with strong opinions among birders on both sides. Whereas some birders prefer using higher magnification to discern greater feather detail and for long-distance birding (for example, hawk watching, seabird watching, or peering into the rainforest canopy), others prefer the slightly brighter image and wider field of view offered by 7x or 8x binoculars. Hand-shake can also be an issue for people who are not used to 10x binoculars, but this also depends on the weight and ergonomics of the particular model. If you opt for lower-priced binoculars (under $400), we generally recommend using only lower-magnification models.

Ergonomics and eyeglass friendliness: As with wines, the many subtle variations in binocular design make it all the more important to “taste” as many binoculars as you can before buying. Our reviewers made copious comments on the weight, balance, ease and closeness of focus, and overall feel of each model. There were as many opinions as there were sizes and shapes of hands and faces, with each reviewer keying in on different features. If you wear eyeglasses while birding, eye-relief is the all-important metric, and fortunately most binoculars now provide an excellent image for us bespectacled types.

Corporate sustainability and conservation: With so many choices in binocular manufacturers and distributors, consumers may also consider what the companies give back to the birding community and to conservation. Several optics companies are major contributors to nonprofit birding and conservation organizations, support bird expeditions or research projects, or provide optics for international birding guides and students. Here at the Cornell Lab, for example, we are particularly grateful for generous support from Zeiss and Swarovski Optik and for their long-term commitment to our mission. We urge all companies to support these important activities and publicize them to the birding community.

More Info to Help You Choose

These interactive graphs will help you pinpoint the price range and attributes that are right or you.

How Much Should You Spend?

Click the image to compare binocular prices against our Quality Index for all 102 binoculars.


How Much Will You See?

Click the image to explore close focus and field of view for all 102 binoculars.


OUR METHODOLOGY

To sort through the mounds of binoculars we received for review, we used a similar approach to past reviews, assembling a small army of 60 “binocular-tasters” on the patio at the Cornell Lab of Ornithology for several days in May. On our first afternoon, a locally rare Prothonotary Warbler fed along the edge of Sapsucker Woods pond, bedazzling reviewers who got to compare its beauty side-by-side through a wide range of optics. We asked each taster to rate at least five binocular models on a 1-to-5 scale, in terms of (1) clarity and crispness of image, (2) overall feel (ergonomics, weight, ease of focus), (3) eyeglass friendliness (eye-relief and sturdiness of the eyecups), and (4) overall performance (“Would you buy these binoculars?”). We then combined these ratings with our own rankings to derive an overall Quality Index, presented as the familiar “1-star” to “5-star” rating. Below we provide our Top Picks in each of five price categories.

TOP PICKS

Top-of-the-line ($2,000 to $2,775, median $2,400)

When crafting the world’s finest burgundy or pinot noir, wine-makers take extreme care every step of the way. Creating the world’s finest optics is very similar. This category brings together an outstanding suite of products. Choosing among the Top Picks comes down mostly to your personal preference. “Tasting” them for yourself is an important step, but at the same time you really can’t go wrong with any of the top models. We decided not to name a “Best in Class” for this top category, because the “tasters” scores were so similar. Among the 15 models in this category, the Zeiss Victory T* HT, Swarovski Swarovision, and Leica Ultravid HDs were the three favorites. Some people were critical of the warping, or “fishbowl” effect, apparent in the new Swarovisions, more so in the 8x than 10x models. Our reviewers also loved several top-of-the-line 8吜 binoculars, which offer the same exceptional optical quality in a smaller, lighter, and less-expensive option. Although the 8x32s may not be as bright in low-light conditions, we believe their benefits may outweigh the rare situations when someone might need that extra bit of light. Get full recommendations, ratings, and specs for all our Top Picks in our online review.

★ ★ ★ ★ ★ Zeiss Victory T* HT 8否 (29.5 oz.) $2,444

★ ★ ★ ★ ★ Swarovski Swarovision 10否 EL (29.8 oz.) $2,777

★ ★ ★ ★ ★ Zeiss Victory T* FL 8吜 (21.7 oz.) $2,055

★ ★ ★ ★ ½ Leica Ultravid HD 8否 (29.5 oz.) $2,099

★ ★ ★ ★ ½ Swarovski Swarovision 8吜 (20.1 oz.) $2,399

★ ★ ★ ★ ½ Leica Ultravid HD 8吜 (21.3 oz.) $1,899

The New Midrange ($700 to $1,999, median $1,050)

A decade ago, $1,000 was the going rate for top-of-the-line binoculars. These days, high-end optics cost upwards of $2,000, and optics companies have introduced an entirely new class of binoculars around the $1,000 price point. This begs the question, is it worth paying an extra $1,000? This is a question you should answer by trying the binoculars for yourself. We can say several exceptional choices have emerged in this new class. The Zeiss Conquests, particularly the 8x32s, were among the top-scoring binoculars in the entire review. Optically, you will notice a step-up in the high-end category if you are pushing the boundaries of bird identification, trying to resolve differences in seabirds or raptors that are just pepper flakes in the sky. For many birders, however, our Top Picks in the New Midrange will serve you well. We reviewed 21 binoculars in this category, and found Zeiss Conquest, Leica Trinovid, and Vortex Razor led the class. Get full recommendations, ratings, and specs for all our Top Picks in our online review.

★ ★ ★ ★ ★ Zeiss Conquest HD 8吜 (22.4 oz.) $999 (Best in Class)

★ ★ ★ ★ ½ Zeiss Conquest HD 8否 (28.0 oz.) $1,077

★ ★ ★ ★ ½ Leica Trinovid 8否 (31.0 oz.) $1,449

★ ★ ★ ★ ½ Vortex Razor HD 8否 (25.5 oz.) $1,279

★ ★ ★ ★ Swarovski CL 8吚 (23.5 oz.) $1,054

★ ★ ★ ★ Meopta Meostar 8吜 (21.5 oz.) $959

The 400 to 699 Club ($425 to $680, median $530)

There seem to be more and better options in this class each year, with several models offering glass and coatings traditionally used only in high-end optics. All of the Top Picks include ED (extra-low dispersion) or HD (high-definition) glass, designed to enhance contrast, resolution, and color. We tested 27 pairs in this class and found five excellent options. Leading the pack were the Nikon Monarch 7 series 8x42s, the high end in the completely redesigned Monarch line, which ruled the midprice class in past reviews. These offer exceptional value, with a sharp, bright image in a comfortable and fully waterproof body. Nearly identical in terms of reviewer scores, but a bit heavier and pricier were the Opticron Verano BGA HD. Other very good options include the Celestron Granite ED, Eagle Optics Golden Eagle HD, and Vortex Viper HD. Get full recommendations, ratings, and specs for all our Top Picks in our online review.

★ ★ ★ ★ ½ Nikon Monarch 7 8否 (22.6 oz.) $530 (Best in Class)

★ ★ ★ ★ ½ Opticron Verano BGA HD 8否 (27.6 oz.) $641

★ ★ ★ ★ ½ Celestron Granite ED 8否 (26.1 oz.) $440

★ ★ ★ ★ ½ Eagle Optics Golden Eagle HD 8否 (25.7 oz.) $600

★ ★ ★ ★ Vortex Viper HD 8否 (24.2 oz.) $655

The 200 to 399 Club ($210 to $399, median $315)

This group offers remarkable quality for the price. You can even get high-quality ED glass in the Nikon Monarch 5 and Zeiss Terra ED. This category is a mix of longtime favorites including the Nikon Monarch (the 5 is definitely worth the price and a step up from the Monarch 3) and Eagle Optics Ranger. Zeiss Terras are brand new, and represent Zeiss’s first attempt to offer a binocular in this price range. The Opticron Trailfinder 3 WP and Vixen New Foresta HR WP are newer to the North American birding scene and offer diversity to the Top Picks. We reviewed 24 binocular models in this class. Get full recommendations, ratings, and specs for all our Top Picks in our online review.

★ ★ ★ ★ ½ Nikon Monarch 5 8否 (20.8 oz.) $309 (Best in Class)

★ ★ ★ ★ ½ Zeiss Terra ED 8否 (25.4 oz.) $385

★ ★ ★ ★ Opticron Trailfinder 3 WP 8否 (27.0 oz.) $219

★ ★ ★ ★ Eagle Optics Ranger 8否 (22.1 oz.) $333

★ ★ ★ ★ Vixen New Foresta HR WP 8否 (25.0 oz.) $399

Budget Bins (under $200, median $155)

If you are on a tight budget, the options in this price range have never been better. Reviewers were stunned to learn the price of the Celestron Nature DX, after rating them as highly as models many times their price, and the Opticron Oregon 8x32s could well be the best binoculars we’ve seen for kids. Among the remaining 16 models we tested, the Leupold Yosemites are very decent for the low price, and they are available in 6x, 8x, and 10x models. Educators looking to purchase binoculars in quantity to lend to visitors or to outfit a class or afterschool group are unlikely to be disappointed with any of our Top Picks. It’s worth noting, though, that spending less than $100 on a pair of binoculars is likely to lead to a relatively poor birding experience or the need to upgrade quickly also, we have yet to find a pair of compact binoculars that we would recommend for serious birding. Get full recommendations, ratings, and specs for all our Top Picks in our online review.

★ ★ ★ ★ ½ Celestron Nature DX 8否 (23.4 oz.) $185 (Best in Class)

★ ★ ★ ★ Atlas Optics Sky King 8否 (26.7 oz.) $199

★ ★ ★ ★ Opticron Oregon LE WP 8吜 (19.5 oz.) $155

★ ★ ★ ★ Eagle Optics Denali PC 8否 (22.6 oz.) $199

★ ★ ★ ★ Optics Planet OPMOD 8否 (24.7 oz.) $195

★ ★ ★ ½ Leupold BX-1 Yosemite 8吚 (19.0 oz.) $129

CONCLUSION

With so many excellent binoculars on the market, choosing just one pair can be overwhelming, but take comfort in the fact that the overall selection is improving. Binoculars are an essential tool, providing a spectacular window into the natural world for birders and other nature enthusiasts. We hope this review is helpful and that you find a pair of binoculars that suits you. To view a chart rating all of the binoculars tested in this review, visit our website at www.birds.cornell.edu/binos. ♦

Jessie Barry is a member of Team Sapsucker, the Cornell Lab’s Big Day team, and is project leader of Merlin, a new bird-identification app being developed at the Lab. Ken Rosenberg is a conservation biologist at the Cornell Lab and a longtime aficionado of birding optics.

Acknowledgments

We’d like to thank the staff of Wild Birds Unlimited at Sapsucker Woods for their patience in generosity in allowing us to test and re-test many of their binoculars during this review: Barry and Sue Stevens, Walt Blodget, Elise Dentes, Ann Perna, and Ann Spinelli.

We also thank the more than 60 Cornell Lab staff and local bird watchers who provided ratings for binoculars: Joanne Avila, Bernd Blossey, Nick Bruns, Shannon Buckley, Tilden Chao, Russ Charif, Miyoko Chu, Greg Delisle, Henk den Bakker, Marc Devokaitis, Martha Fischer, Tom Fredericks, J. Grenier, Emily Griffiths, Yiaing Guo, Kim Haines-Eitzen, Becky Hansen, Greg Heist, Wesley Hochachka, Marshall Iliff, Eduardo Iñigo Elias II, Sara Keen, Anne Klingensmith, Gary Kohlenberg, Stuart Krasnoff, Amanda Larracuente, Nicola Leckie, Tim Lenz, Pat Leonard, Alberto López, David McCartt, Kevin McGowan, Bill Michener, Charles Mollenhauer, Will Morris, Diane Morton, Mary P., Chris Pelkie, Ruth Pfeffer, Alicia Plotkin, Hugh Powell, Mike Powers, Ashik Rahaman, Syed Rehman, Anne Rosenberg, Jesse Ross, Tom Schulenberg, Sharon, Aisha Siebert, Laura Stenzler, Rob Stevenson, Jae Sullivan, Derrick T., Don Timmons, Benjamin Van Doren, Brad Walker, Peter Wiedmann, Andrea Wiggins, Chris Wood, Suan Yong, and Matt Young.


Introduction

The ability to amplify and detect specific DNA sequences is a powerful tool routinely used for a wide variety of applications including disease diagnostics, qualitative trait loci (QTL) selection and mutant screening. In diagnostic applications, nucleic acid-based analysis has many advantages over more traditional methods such as enzyme or antibody-based assays offering increased sensitivity, faster sample-to-answer results, and flexibility as it can be rapidly modified to meet new challenges as they arise [1]. However, the major bottleneck preventing the widespread adoption of molecular diagnostics outside the modern laboratory environment is the requirement to purify nucleic acids from samples, which is a complex task that traditionally requires trained technicians and involves many liquid handling steps [2–4].

The demand for simpler and more rapid nucleic acid purification methods resulted in the expansion of commercially available solid-phase extraction kits. A large majority of these kits are based on the binding of nucleic acids to a solid silica support in the presence of a chaotropic salt [5–8]. Contaminants are then removed by a series of wash and centrifugation steps before finally eluting the nucleic acids from the silica in a low salt solution. Commercially available paramagnetic beads with a variety of different functionalised surface chemistries designed to capture and purify nucleic acids have become available, removing the need for centrifugation [9–11]. In these systems, a magnet is used to attract and hold the paramagnetic beads to the side of the tube to allow supernatant removal during the wash and elution steps. Even though paramagnetic particle-based nucleic acid purification is relatively fast (approximately 10 minutes) and does not require electrical equipment, it is still too complicated for applications that are performed outside the modern laboratory environment such as field-based point-of-need (PON) assays.

Recent publications have reported rapid nucleic acid extraction using different types of membranes including aluminium oxide, the cellulose-based Flinders Technology Associates (FTA) cards (GE Healthcare, USA), and the silica-based Fusion 5 filters (GE Healthcare, USA) [12–18]. These new methods simplified the nucleic acid purification process by eliminating the need for a separate nucleic acid elution step by directly amplifying the nucleic acid off the membrane. This is an advantage over many of the other solid-phase extraction techniques as either the surface chemistries of the matrix or the residual reagents attached to them (e.g., ethanol, chaotropic salts) inhibit DNA amplification [17,19]. However, despite eliminating the elution step, all of these methods require relatively complex fabrication or experimental set ups, multiple pipetting steps, or electrical equipment to help purify the nucleic acids, which, again, limit their usefulness for field-based assays.

Cellulose-based DNA binding is ideal for molecular diagnostics as it is inexpensive, portable, disposable, and easily modified [20–22]. Therefore, we set out to develop a nucleic acid purification method using cellulose paper that does not require any complex fabrication or specialized equipment such as pipettes and centrifuges. Herein, we describe a simple, equipment-free method that can purify nucleic acids from a wide range of plant, animal, and microbe samples within less than 30 seconds, and is therefore equally suited to nucleic acid-based applications both within and outside the modern laboratory environment.


Protected area networks and savannah bird biodiversity in the face of climate change and land degradation

The extent to which climate change might diminish the efficacy of protected areas is one of the most pressing conservation questions. Many projections suggest that climate-driven species distribution shifts will leave protected areas impoverished and species inadequately protected while other evidence suggests that intact ecosystems within protected areas will be resilient to change. Here, we tackle this problem empirically. We show how recent changes in distribution of 139 Tanzanian savannah bird species are linked to climate change, protected area status and land degradation. We provide the first evidence of climate-driven range shifts for an African bird community. Our results suggest that the continued maintenance of existing protected areas is an appropriate conservation response to the challenge of climate and environmental change.

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INTRODUCTION

Earth's biodiversity is essential to human well-being, but the expanding scale of human activities severely threatens it (Johnson et al., 2017 ). For geographical and historical reasons, transboundary regions often contain critical ecosystems that support rich biodiversity and play important roles in maintaining connectivity (Liu et al., 2020 ). More than half of terrestrial vertebrate species have ranges spanning international borders (Mason et al., 2020 ), yet transboundary conservation has so far focused on a few flagship species, such as mountain gorillas (Gorilla beringei beringei), Amur tigers (Panthera tigris altaica), and the eastern black crested gibbon (Nomascus nasutus), largely neglecting other species (Liu et al., 2020 ). Some species can disperse outside of existing protected areas (PAs) or shift their distributions by crossing international borders in response to climate change or human disturbances (Johnston et al., 2013 Urban, 2015 ). However, lack of transboundary planning has put many species in increasing peril through uncoordinated management among neighboring countries, which greatly impairs conservation effectiveness (Mason et al., 2020 Thornton et al., 2018 ). Transboundary conservation can also make a major contribution to current efforts to reduce future extinction risks by increasing the area protected, in accord with the zero draft of the Convention on Biological Diversity's (CBD) post-2020 global biodiversity framework in which a target of 30% of land and oceans by 2030 is proposed (CBD, 2020 ). Appropriate spatial prioritization is crucial for both transboundary conservation and achieving the CBD's proposed target because it can ensure that most important areas for biodiversity are included and PAs are well-connected within and across borders (Thornton et al., 2018 Hannah et al., 2020 ).

Species distribution mapping and land–use change analysis are widely used in conservation planning. Spatially explicit maps can help identify priority areas for biodiversity conservation (Zhang et al., 2012 ). Land-use change caused by human activities alters landscape structure, which may hinder or promote dispersal and migration of species and ultimately influence population viability (Hanski, 2011 Saura et al., 2014 Martensen et al., 2017 ). Landscape connectivity is determined by the dispersal abilities of species and the spatial configuration of habitat patches in the landscape (Saura & Rubio, 2010 Saura et al., 2011 ). Changes in connectivity over time as a consequence of land-use change may determine whether a species can persist in a landscape in the long term (Metzger et al., 2009 ). Generally, specialist forest-inhabiting species, such as small mammals and insectivorous birds, disperse poorly across unforest areas and are thus expected to be at increased risk of extinction when connectivity decreases (Martensen et al., 2012 ). Differing land-use policies between adjacent countries can reduce connectivity in transboundary regions, leading to weakened conservation effort. Therefore, assessing changes in connectivity is essential for strengthening biodiversity conservation in transboundary areas.

China's Yunnan province borders Myanmar, Laos, and Vietnam the total border length is 4060 km. This region is largely in the Indo-Burma biodiversity hotspot, yet habitat destruction and hunting have caused declines in wildlife populations (Myers et al., 2000 Xu & Wilkes, 2004 Harrison, 2011 Hughes, 2017 ). Despite forceful appeals for transboundary conservation, the spatial distributions of biodiversity and threats to landscape connectivity in the transboundary region remain unknown because there have been few biodiversity surveys and little transboundary sharing of data (Wang et al., 2016 Basnet et al., 2019 Liu et al., 2020 ). We integrated species distribution patterns and recent land-use change and determined the change of landscape connectivity for natural forest in the transboundary region to identify priority transboundary areas for conservation and restoration.


Key Features

  • Includes new chapters on endocrine disruptors, magnetoreception, genomics, proteomics, mitochondria, control of food intake, molting, stress, the avian endocrine system, bone, the metabolic demands of migration, behavior and control of body temperature
  • Features extensively revised chapters on the cardiovascular system, pancreatic hormones, respiration, pineal gland, pituitary gland, thyroid, adrenal gland, muscle, gastro-intestinal physiology, incubation, circadian rhythms, annual cycles, flight, the avian immune system, embryo physiology and control of calcium
  • Stands out as the only comprehensive, single volume devoted to bird physiology
  • Offers a full consideration of both blood and avian metabolism on the companion website (http://booksite.elsevier.com/ 9780124071605). Tables feature hematological and serum biochemical parameters together with circulating concentrations of glucose in more than 200 different species of wild birds

Thylacine Was Smaller Than Previously Estimated

Until its extinction, the thylacine (Thylacinus cynocephalus) was the largest living carnivorous marsupial, but little data exist regarding its body mass, with an average of 29.5 kg the most commonly used estimate. However, a new study shows the extinct predator, also known as the Tasmanian tiger, only weighed about 16.7 kg on average.

Tasmanian tigers (Thylacinus cynocephalus) in captivity. Image credit: University of Melbourne / Museums Victoria.

Despite extinction in the 1930s and film footage, the thylacine is a true enigma with almost no direct observations supporting an understanding of their behavior and biology.

Only four reliable records of its body mass can be found in the peer-reviewed literature: 15 kg for an ‘excessively fat’ male a 14.97 kg male, and two records from the 1914 death registry of the London Zoo, a 13.2 kg female and a 26.1 kg male.

Beyond these four records, reported thylacine body masses are scant, anecdotal, and problematic, leaving scientists with no clear record of adult body mass.

“We wish we could watch just how the thylacine hunted, and what sort of prey it could take — this is our closest look yet at an essential ingredient of the predator’s behavior, how big it really was,” said co-author Dr. Alistair Evans, a researcher in the School of Biological Sciences at Monash University and Museums Victoria.

Using traditional measurement techniques, advanced 3D scanning and volumetric methods, Dr. Evans and colleagues estimated body mass for 93 adult thylacines, including two taxidermy specimens and four complete mounted skeletons, representing 40 known-sex specimens.

The scientists established that there were strong differences in the average male and female body size, with the male mean of 19.7 kg and female mean of 13.7 kg.

The mixed sex population mean of 16.7 kilograms is then well below the 21 kg threshold for when predators are likely to take large prey.

“We demonstrate strong differences in average male and female body size,”
Adams

“This result also fundamentally challenges prior views about the thylacines as a carnivore, and underscores that thylacines were a predator that evolved to consume prey smaller than themselves.”

The newly established body mass estimates for thylacines place them as specialists on small prey, challenging prior interpretations of them as convergent with species like wolves that specialise in pack-hunting prey substantially larger than themselves.

“Rewriting the thylacine as a smaller animal changes the way we look at its position in the Australian ecosystem — because what a predator can (and needs to) eat is very much dependent on just how big they are,” said lead author Douglass Rovinsky, a Ph.D. student in the Department of Anatomy and Developmental Biology, Biomedicine Discovery Institute, Monash University

“Many of the 19th century newspaper reports just might have been ‘tall tales’ — told to make the thylacine seem bigger, more impressive… and more dangerous!”

The results were published in the Proceedings of the Royal Society B.

Douglass S. Rovinsky et al. 2020. Did the thylacine violate the costs of carnivory? Body mass and sexual dimorphism of an iconic Australian marsupial. Proc. R. Soc. B 287 (1933): 20201537 doi: 10.1098/rspb.2020.1537


Chronobiology: The Science of Time

Most of us have very little knowledge about the human body’s inner clock. However, a young science from Europe called Chronobiology has been gaining importance over the past 30 years. Chronobiology refers to the day-night cycle that affects the human organism when the earth rotates. Since the beginning of mankind, human history has been shaped by light and darkness. Genetically manifested timers reside deep in our bodies that control this fundamental rhythm. The more intelligently we absorb their information, the more useful it is. This connection is important in the prevention and treatment of diseases, as well as for the healing process.

The beginnings of Chronobiology date back to the 18th century. The astronomer Jean Jacques d’Ortous de Mairan reported daily leaf movements of the mimosa. Through experimentation he was able to show that the leaves continue to swing in a circadian rhythm, even in permanent darkness. Renowned scientists like Georg Christoph Lichtenberg, Christoph Wilhelm Hufeland, Carl von Linné, and—most importantly—Charles Darwin reported similar rhythmic phenomena. Yet it wasn’t until the 20th century when chronobiology research truly began. Wilhelm Pfeffer, Erwin Bünning, Karl von Frisch, Jürgen Aschoff, Colin Pittendrigh and Arthur Winfree are among its pioneers.

The Three Basic Cycles of Chronobiology

Infradian Rhythms

(derived from the Latin word infra, meaning “below,” and the Latin word diem, meaning “day” – breaking down the origin of the word, Infradian means the period of this rhythm is longer than 24-hours, therefor, the frequency is below/under those of one day.)

These are rhythms that last more than 24 hours. These are repeated only every few days, weeks, months, or even once per year.

Good examples are seasonal rhythms such as bird migration, lunar rhythms (which follow the phases of the moon, or about 29.5 days) and semi-lunar rhythms (about 14 days) that are associated with tidal cycles. Another example is unpredictable rhythms (aka “non-circadian rhythms” that do not have any environmental correspondence) such as a woman’s menstrual cycle.

Ultradian Rhythms

(derived from the Latin ultra, meaning “beyond,” and from the Latin word diem, meaning “day” – breaking down the origin of the word, Ultradian means the period of this rhythm is shorter than 24-hours, and therefor has a frequency beyond/higher than one day.)

These are biological rhythms that are shorter than 24-hours. There are many physiological functions of the human body that exemplify an ultradian rhythm. These rhythms have multiple cycles in one day. An adult, for example, has an exertion and rest cycle about every two hours.

Ultradian rhythms regulate physical, emotional and spiritual functions. They often last several hours and include the ingestion of food, circulation of blood, excretion of hormones, different stages of sleep and the human performance curve. These processes are built into our bodies in millions of ways. Some last merely seconds, such as the control of breathing. Some last only milliseconds, such as the majority of processes that take place in the cell on a microcirculatory level. Tidal rhythms (about 12.4 hours) are often observed in marine life, follow the transition of the tides from high to low and back and have a special function for many people living inside a surf zone.

Circadian Rhythms

(from Latin “circa” meaning “around,” and “diem” meaning “day”)

These are rhythms that take approximately 24-hours, i.e. the human sleep/wake cycle or the leaf movements of plants. Many effects of circadian rhythms directly and immediately affect humans, therefore, they are the most extensively researched. Thus, all further explanations refer to circadian rhythms.

Chronobiology Today

The field of chronobiology is rapidly expanding around the world. Medical professionals, researchers and the general population are beginning to see the benefits of using chronobiological principles in everything from medication administration to determining the most effective time of day to exercise. Chronobiology is being used in the study of genetics, endocrinology, ecology, sports medicine and psychology, to name a few.

The chronopharmacology branch of chronobiology has been especially lucrative. Thousands of studies have yielded information on how the precise timing of a medication or supplement can decrease side effects, have a more potent effect on the target organ system or disease and even completely disrupt a physiological process.

Many renowned institutions have added departments, labs and curriculum centered on the study of chronobiology. These institutions have provided groundbreaking research and insights that have helped shape modern medicine and the understanding of our innate biological rhythms. Melatonin, also referred to as the “mother hormone of chronobiology,” the effects of light on a variety of diseases and the phenomenon of chronotypes have been areas of particular interest.

While chronobiology is still considered a young science, the possibilities it presents are endless. Our methods of research are becoming more advanced and with that brings the reality that chronobiology will eventually become the leading scientific discipline.


Animal Diversity Web

Leatherbacks are primarily pelagic animals. They travel great distances from their nesting beaches to their feeding grounds. Although leatherbacks are most often found in tropical waters, they are distributed around the globe in temperate oceans, and even on edges of subarctic water. The leatherback sea turtle travels further north than any other sea turtle. They live in Northern Atlantic waters as far north as Newfoundland, Nova Scotia, and Labrador. They also inhabit South Atlantic Waters, as far south as Argentina and South Africa. This turtle inhabits waters as far east as Britain and Norway.

During the nesting season they are discovered along the coasts of French Guiana, Suriname, Guyana, Trinidad, Gabon, West Africa, Parque Marino Las Baulas in Guanacaste, Costa Rica, Papua New Guinea, Andaman and Nicobar Islands, Thailand, in the U.S. on St. Croix, U.S. Virgin Islands, and in Puerto Rico and Florida. The largest nesting colony is in Africa, along the coast of French Guiana. More than 7,000 females laid as many as 50,000 eggs there in 1988 and again in 1992. There is one nesting record in Cape Lookout, North Carolina. (Eckert, 2006 Martof, et al., 1980 Spotila, 2004)

Habitat

Leatherback sea turtles live in many different oceans throughout the world. They are widely known as pelagic animals but are seen in coastal waters when searching for food. They live in tropical, temperate and even some subarctic oceans. They have been discovered in waters as deep as 1230 m, well below the photic zone.

Leatherbacks lay their eggs in the sand of tropical beaches. It is the only time they emerge onto land, and only the females do so. (Eckert, 2006 Spotila, 2004)

  • Habitat Regions
  • temperate
  • tropical
  • saltwater or marine
  • Aquatic Biomes
  • pelagic
  • coastal
  • Other Habitat Features
  • intertidal or littoral
  • Range depth 1230 (high) m 4035.43 (high) ft

Physical Description

The leatherback sea turtle is the largest of living turtles. It may reach a length of ca. 2.13 m. Adults may have a span of ca. 2.7 m from the tip of one front flipper to the tip of the other. They have a secondary palate, formed by vomer and palatine bones. The leatherback has no visible shell. The shell is present but it consists of bones that are buried into its dark brown or black skin. It has seven pronounced ridges in its back and five on the underside. Leatherback hatchlings look mostly black when looking down on them, and their flippers are margined in white. Rows of white scales give hatchling leatherbacks the white striping that runs down the length of their backs.

These turtles feed in waters that are far colder than other sea turtles can tolerate. They have a network of blood vessels that work as a counter-current heat exchanger, a thick insulating layer of oils and fats in their skin, and are able to maintain body temperatures much higher than their surroundings. (Spotila, 2004)

  • Other Physical Features
  • ectothermic
  • heterothermic
  • bilateral symmetry
  • Sexual Dimorphism
  • female larger
  • Range mass 250 to 900 kg 550.66 to 1982.38 lb
  • Range length 145 to 160 cm 57.09 to 62.99 in

Development

Hatching success of clutches is about 50% in an undisturbed nest. Many nests are destroyed by many different predators. Nest temperature determines the hatchlings' sex. At 29.5 degrees Celsius hatchlings are equally likely to be male or female, hatchlings incubated at 28.75°C or less will be male, above 29.75°C they'll be female. Hatchling turtles weigh 35-50 grams, and grow very fast. Leatherbacks may be the fastest growing reptile in the world, reaching adult size in 7 - 13 years. (Spotila, 2004)

Reproduction

The male leatherback turtles will migrate just offshore a common nesting beach generally before nesting season begins. There they will try and mate with as many females as possible. Also, studies have shown that the males will return to the same nesting beach if they were successful in the previous season. (Eckert, et al., 2005)

Leatherback sea turtles mate in the water, just offshore from the females' desired nesting beach. The female then swims ashore at night to nest and will produce a clutch of usually 50 - 170 eggs. However, a large percentage of those eggs are yolkless and will not develop further. The female will lay her eggs and then cover the nest with sand to discourage predation and moderate the temperature and humidity around the eggs. After the female has completed this process she will returns to the ocean. Male leatherback sea turtles never swim to shore and have no part in the nesting process. (Barbour and Ernst, 1972 Beacham, et al., 2000 Eckert, et al., 2005 Zug and Parham, 1996)

  • Key Reproductive Features
  • semelparous
  • seasonal breeding
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • fertilization
  • oviparous
  • Breeding interval Leatherback Sea Turtles will lay about 5 to 7 nests per year, renesting every 9 to 10 days. Also, they will return to the same nesting location every 2 to 3 years.
  • Breeding season They generally reproduce between the months of April and November.
  • Range number of offspring 50 to 70
  • Average number of offspring 105 AnAge
  • Range gestation period 55 to 75 days
  • Average time to independence immediate (no parental investment past egg-laying) minutes
  • Range age at sexual or reproductive maturity (female) 5 to 21 years

The only parental investment that occurs with leatherback sea turtles is when the female lays eggs on the shore and covers her nest after laying the eggs. No subsequent parental care occurs. (Barbour and Ernst, 1972)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female

      Lifespan/Longevity

      We have no information on the lifespan of Dermochelys coriacea . (Barbour and Ernst, 1972 Pope, 1939)

      Behavior

      Leatherbacks are mostly solitary. They migrate great distances between nesting and feeding grounds. They seem to locate locations that have high concentrations of jellyfish, and feed near the surface or dive to find the highest concentrations of prey. (Alderton, 1988 Carr, 1952 Pope, 1939)

      Food Habits

      Leatherback turtles are carnivores that feed in the open ocean. Their main prey are gelatinous invertebrates, mainly jellyfish and salps. They are known to eat other kinds of food though, including small crustaceans and fish (possibly symbiotes with jellies), cephalopods, sea urchins, and snails.

      Leatherbacks do not have the powerful muscles and hard crushing jaw apparatus that some other sea turtles have for eat hard-shelled prey. Instead they have sharp-edged jaws for biting soft-bodied prey. The esophagus in this species is lined with short spines that point downstream, preventing jellies from escaping once swallowed. (Caut, et al., 2006 Houghton, et al., 2006)

      • Primary Diet
      • carnivore
        • eats other marine invertebrates
        • Animal Foods
        • fish
        • mollusks
        • aquatic or marine worms
        • aquatic crustaceans
        • echinoderms
        • cnidarians
        • zooplankton

        Predation

        In modern times, humans have become the primary predator of this species, gathering eggs and killing adults.

        Leatherback turtles eggs are consumed by a large variety of predators, including ghost crabs (Ocypode), monitor lizards (Varanus), wading birds such as turnstones (Arenaria), knots (Calidris), and plovers Pluvialis). Many mammals excavate nests as well, including raccoons (Procyon lotor) and coatis (Nasua), dogs (Canis), genets (Genetta), mongooses (Herpestidae) and pigs (Suidae). Most of these same predators will take hatchlings as the little turtles race for the sea, as will raptors (Falconiformes), gulls (Larus), and frigate birds (Fregatidae). In the ocean, small leatherbacks are attacked by cephalopods, requiem sharks (Carcharhinidae) and other large fish. Adult leatherbacks are large and powerful enough to have few predators, but jaguars (Panthera onca) and other large predators may attack nesting females, and killer whales (Orcinus orca) and large sharks may attack them at sea.

        Nesting females pack the sand over their clutch of eggs, perhaps to obscure the scent of the eggs and make them harder for small predators to dig up. Hatchlings wait until nightfall to emerge and head for the water, to avoid predators. Throughout their lives leatherbacks are counter-shaded, dark on the dorsal surface and light underneath, to better blend with background light (though the dark dorsal surface is probably also better for basking).

        Although they don't have the bony shell of most turtles, they do have a thick layer of connective tissue over bony plates covering much most of their body. Leatherbacks are strong and fast swimmers, and adults may defend themselves aggressively. One adult (c. 1.5 m long) was seen chasing a shark that had apparently attacked it, and once the shark fled, the turtle attacked the boat that the observers were in. (Caut, et al., 2006 Chiang, 2003 Ernst, et al., 1994)

        • Known Predators
          • ghost crabs (Ocypode)
          • monitor lizards (Varanus)
          • turnstones (Arenaria)
          • knots (Calidris)
          • plovers Pluvialis)
          • raccoons (Procyon lotor)
          • coatis (Nasua)
          • genets (Genetta)
          • dogs (Canis lupus familiaris)
          • mongooses (Herpestidae)
          • pigs (Sus)
          • cephalopods (Cephalopoda)
          • requiem sharks (Carcharhinidae)
          • killer whales (Orcinus orca)
          • frigate birds (Fregatidae)
          • vultures and hawks (Falconiformes)

          Ecosystem Roles

          Leatherback sea turtles are predators that eat mainly jellyfish and other soft-bodied marine animals. Their affect on prey population densities is unknown, but might have been substantial before their populations were reduced by harvesting.

          Leatherback eggs and hatchlings may be a significant food source for egg predator populations near their nesting beaches.

          Economic Importance for Humans: Positive

          Although the flesh of adult leatherbacks can sometimes be toxic, adults and eggs are used for food in some locations, and in a few places the oil from the bodies of adults is extracted for medicinal use and as a waterproofing agent.

          Leatherbacks eat jellyfish that are pests for swimmers and fishermen, especially for marine fish-farming. Consumption estimates vary, one study estimated that adult leatherbacks probably eat about 1000 kg of jellyfish per year, an earlier study estimated 2900-3650 kg/yr. (Spotila, 2004 Ernst, et al., 1994 Spotila, 2004 United States Fish and Wildlife Service, 2007)

          Economic Importance for Humans: Negative

          This species does not harm humans or cause significant costs. It's flesh is sometimes toxic to humans and other animals, perhaps due to toxins ingested as part of its diet of jellyfish.

          Conservation Status

          This species is believed to be in serious decline. Populations of nesting females in the Pacific have declined as much as 70-80% in the last decade, and the status of the Atlantic population is unclear. Because females may nest on more than one beach each year, accurate counts are more difficult than for some other turtle species. The species is rated "Critically Endangered" by the IUCN, and "Endangered" by the U.S. Fish & Wildlife Service. It has been listed in Appendix I of the CITES, making any international trade illegal.

          The primary threat to the species is commercial fishing: turtles accidentally trapped and drowned in nets and trawls, or hooked or tangled by longlines and trap lines. Harvesting of eggs is a significant problem as well. Also, leatherbacks apparently sometimes eat plastic debris they find in the water, probably mistaking it for jellyfish. This plastic debris is indigestible, and an increasing number of turtles are found dead with blocked digestive tracts.

          Nature reserves have been established in the coastal areas where the turtles come to breed to prevent people from stealing the eggs. In some areas, scientists have taken the eggs into captive breeding programs to try to increase the population of the area. Some governments require use of turtle-exclusion devices on fishing gear, but this is not a widespread practice. (Ernst, et al., 1994 National Oceanic and Atmospheric Administration, Office of Protected Resources, April 13, 2001)

          In July of 2004, the “Marine Turtle Conservation Act” was signed into law in the United States. The purpose of this bill was to aid in the conservation of marine turtles, as well as to assist foreign countries in preserving their nesting habitats. To support this bill there are hopes of creating a “Multinational Species Conservation Fund” to support conservation of imperiled marine turtles, including the leatherback. (Evans, 2004)

          • IUCN Red List Critically Endangered
            More information
          • IUCN Red List Critically Endangered
            More information
          • US Federal List Endangered
          • CITES Appendix I

          Contributors

          Adam Farmer (author), Radford University, Annamarie Roszko (author), Radford University, Scott Flore (author), Radford University, Kevin Hatton (author), Radford University, Veronica Combos (author), Radford University, Andrea Helton (author), Radford University, Karen Powers (editor, instructor), Radford University.

          Fermin Fontanes (author), University of Michigan-Ann Arbor.

          Glossary

          the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

          body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

          having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

          an animal that mainly eats meat

          the nearshore aquatic habitats near a coast, or shoreline.

          animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

          union of egg and spermatozoan

          A substance that provides both nutrients and energy to a living thing.

          having a body temperature that fluctuates with that of the immediate environment having no mechanism or a poorly developed mechanism for regulating internal body temperature.

          the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.

          makes seasonal movements between breeding and wintering grounds

          having the capacity to move from one place to another.

          the area in which the animal is naturally found, the region in which it is endemic.

          islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

          reproduction in which eggs are released by the female development of offspring occurs outside the mother's body.

          An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

          an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).

          the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

          mainly lives in oceans, seas, or other bodies of salt water.

          breeding is confined to a particular season

          offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.

          reproduction that includes combining the genetic contribution of two individuals, a male and a female

          that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

          the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

          animal constituent of plankton mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

          References

          Bronsgerma, L.D. Guide for the identification of standard turtles of British Coasts. London, British Museum of Natural History.1976.

          Bustard, H. Roberts. Sea Turtles and the Turtle Industry of the West Indies, Florida and the Gulf of Mexico. Coral Gables. Fla., University of Miami Press (1974).

          Chang, Eng Heng. The Leatherback Sea Turtle:a Maylasian Heritage. Kuala Lumpur, Malaysia: Tropical Press Sdn. Bhd.,1989.

          Hartog, J.C. den. A study on the gut content of six leathery turtles Dermochelys coricacea:(Linneaus)(Reptilia:Testudines:Dermochelydae) from British waters and from the Netherlands. Leiden: Rijiksmuscum van Natururlijke Historie. 1984

          Recovery Plan for the St. Croix population of Leatherback turtle. Washington D.C.: United States Fish and Wildlife Service. 1981.

          Encyclopaedia Britannica, Inc. Peter B. Norton, Joseph J Esposito. Chicago. Vol.10, Vol. 11, Vol. 25, Vol. 26. 1986.

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          A medium-sized hawk with the classic accipiter shape: broad, rounded wings and a very long tail. In Cooper’s Hawks, the head often appears large, the shoulders broad, and the tail rounded.

          Relative Size

          Larger than a Sharp-shinned Hawk and about crow-sized, but males can be much smaller.

          crow-sized

          Measurements
          • Male
            • Length: 14.6-15.3 in (37-39 cm)
            • Weight: 7.8-14.5 oz (220-410 g)
            • Wingspan: 24.4-35.4 in (62-90 cm)
            • Length: 16.5-17.7 in (42-45 cm)
            • Weight: 11.6-24.0 oz (330-680 g)
            • Wingspan: 29.5-35.4 in (75-90 cm)

            Adults are steely blue-gray above with warm reddish bars on the underparts and thick dark bands on the tail. Juveniles are brown above and crisply streaked with brown on the upper breast, giving them a somewhat hooded look compared with young Sharp-shinned Hawks' more diffuse streaking.

            Look for Cooper’s Hawks to fly with a flap-flap-glide pattern typical of accipiters. Even when crossing large open areas they rarely flap continuously. Another attack maneuver is to fly fast and low to the ground, then up and over an obstruction to surprise prey on the other side.

            Wooded habitats from deep forests to leafy subdivisions and backyards.


            Watch the video: Birds Vertebrates. Biology. Nature (August 2022).