Today I found the first casualty at the Noble Research Center since late October, 2014: a Northern Mockingbird at the northeastern alcove. This was one of those birds that would have been really difficult for me to overlook.
Now a mockingbird would presumably be a resident, and the mocker who seems to have laid claim to this corner of campus was singing his head off while I conducted my rounds. Was this his mate? Nope – my examination suggested that this was a male by his rather conspicuous cloacal protuberance. Was it a local rival? It would be pretty cool to think of the resident male driving this guy to his death my making him collide with a window. I doubt that though and here’s why: this was the fattest mockingbird I had ever seen. It was easy a “2” by my scoring, with the furcular hollow more than half full. The only reason I can see for a mockingbird to have accumulated fat would be if it was in passage. This otherwise resident species was most likely an individual of that species on his way back north to some portion of the species’ range where mockers bug out for the winter.
Migration is fraught with difficulty and real danger. Many birds experience the highest mortality of their lives while in passage. For many, that risk is worth it for the chance to exploit some environmental conditions in spring and summer that are excellent for the production of the next generation. For some like this guy, the gamble doesn’t pay off.