In previous Keeper Stories, I’ve written to you about the importance of different types of beaks and feet. Well, I’m back to discuss another important part of a bird’s anatomy with you: the wings!
It has always been fun to remind people that the forelimbs of birds, though appearing vastly different with their array of feathers, are considered homologous structures to the human arm. Homologous structures are body parts with similar features that indicate a common ancestor; the examination and comparison of homologous structures allowed early scientists to make connections such as “mammals and birds have a more recent common ancestor than birds and fish.” From the humerus down to the phalanges, the same bones found in our arms exist in a bird’s wing. All birds have wings, though some, such as the cassowary or kiwi, have reduced vestigial structures. While the anatomy is fascinating, I have recently been intrigued more by the use of wings.
The most obvious use is flight, which I promise I will discuss in a bit, but there are other functions for these limbs. Well demonstrated by the members of the Columbiformes (i.e. pigeons and doves) is the art of self-defense. Very often, whenever a pigeon is trying to protect themselves or what they deem as theirs, their first instinct is to raise their wings to intimidate any potential aggressor or thief, only to follow with a nice quick smack. We call this “wing-slapping,” and while you could imagine the feathers softening the blow, getting pummeled by the humerus of any bird is certainly not a pleasant experience. Our most notable employers of this tactic are none other than the Victoria crowned pigeon pair found in the Grigsby Aviary. Another example of weaponized wings comes in the form of the masked lapwings, just a short walk away from where the Victoria crowned-pigeons are housed. These individuals have small spurs located on their carpal joints; when viewing the birds, this is the spot on their wing (when at a folded, neutral position) that is commonly mistaken for their shoulder but is actually akin to the wrist!
Another use of the bird’s wing is for thermoregulation. You may often see this employed by individuals settling in for a nap or trying to keep the exposed skin on and around their beaks and eyes covered during a cold day. The wings will serve the same role as placing a scarf around your face. Wings also function to help chicks. Not only is hiding under mom or dad’s wings a safe spot, but it is quite toasty there.
Speaking of chicks, to get to the rearing of young, displays are often performed across numerous species of birds using their wings beyond simply relying on vibrant colorations. If you have never had the opportunity of watching courting birds, I highly recommend you spend some time on YouTube. Some immediate recommendations that come to mind include the great argus pheasant, who uses his wings in a very similar fashion to that of our male peafowl’s tail, or almost any bird of paradise will be a true treat.
Then, as promised, there is flight.
As terrestrial-bound organisms, it’s not unreasonable to watch a bird in flight and think of how enthralling such an activity would be. I’ve heard guests muse about the dreamy concept of soaring for hours in the clouds, how effortless it would be to get to a beloved destination, and while those are great wishes, flight serves more purpose than fanciful entertainment. Birds use flight to obtain food, commute to feeding grounds, or perform aerial displays. It’s a form of locomotion that helps them avoid predators via quick take-offs to safety and allows them to nest in spots potentially out of the reach of those same foes. In fact, there are five general wing shapes that allow for different strategies of flight. The different strategies (and examples) are: passive soaring (eagles and hawks), active soaring (albatrosses and gulls), short bursts with elliptical wings (passerines such as crows, sparrows, and robins), high-speed flight (terns, falcons, or swifts), and hovering (hummingbirds).
Still, flight is considered an energetically costly behavior. You can see this by watching the way native robins respond to your approach – their first instinct tends to be to run away and then fly when that does not prove sufficient. Scientists also debate whether the disuse of flight (due to filling an alternative niche or the lack of natural predators) led to losing flight entirely among the species by citing examples such as penguins or the flightless cormorant.
Now, a conversation about wings would not be complete without discussing “wing trims”. A wing trim is the process of trimming a bird’s primary wing feathers or remiges so that it is not fully flight-capable. All feathers are composed of keratin, the same material from which our fingernails are composed. So just as a nail trim is not painful for you, cutting the feathers does not harm the individual involved and is not permanent, but allows them to safely remain in their habitats.
Once more, this is just another feature of birds that strongly ties them together while simultaneously can help differentiate them in so many ways. So, the next time you visit Zoo Atlanta, I implore you to take a moment and watch the birds. Watch them fly and maneuver around their habitats or study which wing shapes might aid in different lifestyles.
Keeper II, Birds