What Does the Ornithologist See? Journey North’s Laura Erickson viewed the same three pictures and shared these observations: Spreading a Wing to Shade the Baby? Bothered by Her Brood Patch? Baby On the Edge! Spreading a Wing to Shade the Baby? Eagles Online My guess is that she’s opening her wing to shade the baby. You can see by the shadows that it’s a sunny day. I don’t know how hot it is, but the eagle is facing away from the sun and appears to be protecting the baby from the sun. The eaglet is pretty fuzzy but has some bald spots and can still get sunburned and overheated. The eaglet is still not perfectly able to thermoregulate, but I’d guess she's more shading it than anything right now. The adult eagle has to be careful not to overheat herself. When a bird gets too warm it doesn’t sweat (their down feathers would absorb the water if they sweated, and could get saturated). Birds can pant to cool down (but we can’t see if she’s panting). They can also spread their feathers to expose bare skin and release heat. Here’s how: When the bird’s skin is relaxed, the feathers cover the skin entirely. However, each feather is attached to its own muscle, and the bird can control the feather to expose skin to air. This gets rid of the heat. On a baby bird you can see the feather tracts really easily. See these baby hummingbirds in their nest. Photo: D. Edington This works because feathers don't grow out of every square inch of the body. Feathers grow on “feather tracts” and there's bare skin between the tracts. So, by moving the feathers and exposing a bald area, heat can escape. Anybody who's had goose bumps has seen how muscles control the tiny hairs on our skin. For humans, it’s an involuntary response to temperature. But birds have control of these muscles. Why doesn't the eagle open the feathers on her back? To avoid sunburn. The skin on birds is very thin. It’s so thin you can sometimes see muscles right underneath. Bird skin doesn't need to be thicker because feathers do many of the jobs skin does (protects from water, sun, cold). Everything birds have must be light weight for flight, so the extra weight of thicker skin is avoided. Bothered by Her Brood Patch? Eagles Online What is a “brood patch”? I noticed that she keeps looking under her, EVEN when the eaglet isn't under her. One guess is that she's checking on the other egg. (Even though the site says it’s not a viable egg, it can take time for the adult to abandon incubation entirely.) Another possibility is that the brood patch on her tummy might still be a bit itchy. (Both male and female eagles have brood patches. The brood patch is more developed on female.) Now that egg incubation has ended the feathers would be growing back about now, and growing feathers are itchy. So it could be she's tugging at new feathers on her belly. Baby On the Edge! Eagles Online Will the baby fall off? I wouldn’t be concerned. Their claws are pretty sturdy even at that young age to protect them from falls. And notice how the edges of the nest are lipped and made of sturdy sticks. The baby has to work to really make it to the edge, and once there, has something to hang onto. Eagles are birds of heights, and babies who are inquisitive and adventurous are still safe in the nest. Copyright 2003 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form