From Our Readers
KEEPING IT COOL
The wonderful article about vultures [“There Goes the Neighborhood,” November-December 2008] has once again led me to question the validity of the concept of urohydrosis, the process by which some birds deposit their uric acid waste products on their legs in order to let evaporation lower their body temperature.
Over the past 40 years, I have always included a live vulture in my educational wildlife programs to illustrate these birds’ marvelous adaptations. Most of them revolve around cleanliness, since vultures stand on, feed on, and stick their heads into large decaying carcasses. The birds’ amazing digestive system allows them to consume spoiled meat that would put humans on their deathbed. When the stomach contents are expelled as a defense mechanism, the horrible stench is an effective deterrent against predators. When the end product of this digestive process is periodically deposited on the legs, it acts as a powerful disinfectant that quickly degrades even the tough leather jesses on a captive bird’s legs.
Several years ago I brought a baby captive-bred Andean condor to the ornithology class I was teaching. A student asked me about urohydrosis, and I asked her to consider the following: With over 9,000 different species of birds on the earth, why would just a handful of them exhibit this adaptation if it was a necessary and important cooling mechanism? Is it just a coincidence that the birds that do defecate on their legs are the same species that stand on decaying carcasses and have other adaptations such as bare heads for cleanliness? Also, why do turkey vultures that remain in the Northeast throughout the winter continue to cool their legs when keeping them warm would seem a higher priority?
I asked the student to draw her own conclusions based upon the evidence. Is the premise of urohydrosis valid, or is it an ornithological myth with a scientific name?
Field Editor Kenn Kaufman responds: The idea that vultures use urohydrosis mainly for temperature regulation is pretty widely accepted, but that doesn’t mean that it’s correct. What Bill Robinson says makes a lot of sense, especially if he has experience with captive vultures that continue to exhibit this behavior in cool weather—that would really suggest that he’s on to something. I encourage him to publish a short note about this in some scientific journal. He doesn’t need exhaustive proof of his theory in order to raise a significant question.
CONNECTING THE DOTS
Audubon does a great job of environmental education in connecting the consequences of man’s actions with the changes in the natural world. The articles “There Goes the Neighborhood” and “Pain in the Glass” [November-December 2008] bring the relationship between man’s urban environment and the causes of increases and declines in bird populations to our attention.
I am happy to see problem solving techniques being developed and discussed in the second article. I believe this type of thinking is what conservationist Aldo Leopold was looking for when he expressed his thoughts on the three things we need to do when making decisions concerning the natural world: maintain ecological integrity, preserve aesthetics, and do what is economically expedient.
Swarthmore College installed fritted glass to help save birds. After the initial investment, the school and the environment saw returns in the form of decreased cooling for the building and saved avian lives. This is what I feel Leopold meant by economic expediency. The connections, reactions, and solutions by reasoning through multifaceted problems of energy conservation, earth-friendly architecture, and reducing bird loss are excellent examples of what we must continue to do. I hope more common citizens and scientists catch on to this type of thinking!
“Put Up Your Guard” [Audubon Living, November-December 2008] discusses birds colliding with windows. When we find a stunned bird, we cup it in our hands to keep it warm until it awakens. The bird’s eyes clear up, and it sits for a few minutes before flying off. Is this okay for the bird? Is there anything else we should be doing to help it recover?
Dick and Judy Pike
St. Cloud, MN
Steve Kress responds: Some birds stunned by collisions with windows recover if they’re retrieved quickly, before a predator finds them. Treat a stunned bird as if it’s in shock. Keep it quiet, warm, and away from loud noises in a no-stress location. Physiologically, a restrained bird (even cupped in your hand) is under major stress, and its instinct is to fly away from danger. Stress causes the body to produce a high level of cortisol, known to impair the body’s ability to heal itself. Although it may seem like a bird is fine, you don’t really know what happens after it flies away.
Give the bird a chance to recover slowly. Put it in a cardboard box slightly larger than the bird so that it doesn’t injure or exhaust itself further by struggling. Place a towel inside the box to provide a surface for the bird to grip, and add a few ventilation holes. Gently place the bird on its feet in the box, propping it upright if needed with a rolled towel or cloth. Don’t force-feed the bird or give it water. Injured birds need to direct their energy to recovery rather than to digesting food; it’s easy to drown a bird by forcing it to drink. Secure the box flaps so the bird doesn’t escape.
Keep the box in a warm spot away from noise for a few hours before peeking inside to reassess the bird’s condition. If it’s ready for release, it will flutter about in the box. If you find a diurnal bird late in the day, keep it in the box overnight, and release it the following morning. If the bird isn’t ready for release, locate your nearest licensed wildlife rehabilitator by calling your state conservation department. Rehabilitators work with veterinarians, so they can often locate someone licensed to work with birds. Except for non-native species like starlings and house sparrows, most wild birds are protected by state and federal laws, so keeping them beyond a temporary recovery is illegal. Successful rehabilitation takes experience and equipment well beyond that found at home.
Re: “Put Up Your Guard.” What has worked for me for eight years in curtailing birds from hitting my windows is bright-colored Slinkies. I put hooks at the top of my windows, drape the Slinkies from hook to hook, then weave another one across the ones that hang vertically. A slight breeze will cause them to move, which helps birds see them. Prior to putting the Slinkies up, I had one or more birds hit my windows daily, but now they don’t come close.
DEPARTMENT OF CORRECTION
In the September-October 2008 Earth Almanac, we wrote that red admiral butterfly caterpillars live in tents made from silk and the leaves of willows, poplars, or elms. This is incorrect. The caterpillars make tents out of plants from the nettle family, most commonly the stinging nettle.
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