Blackpoll Warbler- Dendroica striata
When I went in to the Field Museum a couple of weeks ago, this was the bird that I worked on. It's the first bird I had worked on making in to a study specimen in over a year. I was worried that I would be rusty, but it actually turned out to be a really nice. Or, at least I won't be embarrassed to have it sitting in the collections with my name on it. It was a mature female Dendroica striata. There are a couple of ways to determine that it was a mature female. On passerines (song birds) mature skulls have a sort of stippling pattern throughout the bone. You can really see it when you hold the skull up to a light. Also, I was able to locate her single ovary. During the breeding season, it is relatively easy to locate on a mature bird, as it is somewhat enlarged and full of ovum. The same goes for male birds, as their testes are enlarged during the breeding season. During non-breeding season, it's a different story, as ovary and testes have shrunk to non-breeding sizes. And on a small bird like a warbler, they can be very difficult to locate if you are not a seasoned field biologist.
Blackpoll warbles have an extraordinarily long migration. This little female had traveled all the way from South America most likely, only to end her journey by smacking in to a downtown Chicago building. But we hope that by dedicating her body to research, we can learn more about how to minimize these types of window kills in the future.