The Basics
Birds (class Aves) are one of the most accessible groups of wildlife. They are generally out in the daylight, live in many environments, and are much less timid than most wildlife since they can easily fly away to escape.
In addition to being accessible, they have some of the most spectacular colorings in the animal kingdom, some of the most interesting and complex mating behaviors, and are the last remaining dinosaurs.
The line between “bird” and “dinosaur” has gotten much more blurry over the past 200 years until it has finally been accepted that there isn’t one: birds are part of the same clade. Specifically, theropods, such as velociraptors.
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The closest living relatives of birds are alligators and crocodiles. Crocodilians appear very different than birds and they are not considered dinosaurs, although they are both archosaurs which contains dinosaurs and pterosaurs.
Birds are warm-blooded vertebrates, the only known living endothermic homeotherms besides mammals. They have lightweight skeletons, feathers, and bills. Birds are also bipedal, egg-laying, and have high metabolisms.
How diverse are birds?
More than half of birds belong to the order Passeriformes or perching birds. Passerines are the most derived group. The rest are divided into 22 more orders, all ending in “iformes”. These other orders go from ostriches (Struthioniformes) to parrots (Psittaciformes), from least to most related to the passerines. In other words, from the most ancestral to the most derived.
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Most of the groupings of birds that we refer to in common speech are at the family level. Some of these families include finches (Fringillidae), crows and jays (Corvidae), and sparrows (Passerellidae - not including the unrelated House Sparrow). These examples are all passerine species, but the remaining 22 orders are also divided into families.
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Birds are abundant on every continent and range greatly in size and form, from the Bee Hummingbird (5.5 cm) to the ostrich (280 cm). There are approximately 10,000 species worldwide that are spread between land or ice, air, and sea or freshwater.
This Wild Wonderland, 2021
This Wild Wonderland, 2020
Why is bird anatomy important?
Bird anatomy is important for identification. Looking at key parts of the body, flight patterns, and overall shape can often help you identify birds at least to family and often to species.
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Bird anatomy helps us understand taxonomic relationships. Looking at bird skeletal structure can show us how birds are related to dinosaurs, alligators, and other reptiles. It can also show us how different groups of birds are related to each other.
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Bird anatomy can also help us understand the basic physics and concepts of flight. Bird anatomy is essential to their flight, both in their lightweight, hollow bones and in their contoured, strong feathers.
How do birds reproduce?
Most birds are socially monogamous, meaning that a mated pair will raise offspring cooperatively. However, many of these bird species are polygynous and some are polyandrous.
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Many birds have extravagant displays to attract mates. This can include vibrant colors and feathers, elaborate dances, and complex and unique songs. Male birds invest many of their resources into producing these displays, so there must be a very strong payoff in the number of offspring these displays allow them to sire.
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Male and female birds possess an internal cavity known as a cloaca which opens to reveal their reproductive organs - testes or ovaries. In order to mate, two individuals rub their cloacas together, which swell outside of their bodies during mating season. The female will then lay fertilized eggs which will typically be incubated by one or both of the parents until they hatch. Even after hatching, birds typically invest much of their time into raising these offspring.
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