Tuesday, March 29, 2005



Wondering if you could ask your friend John Blakeman if he knows of any way to identify individual kestrels. We have a pair that has moved into the nestbox we installed, and we're watching anxiously via the nestbox cam (and hundreds of people are watching on the Internet) to see how many eggs she lays (3 so far) and how many chicks hatch, etc. But we've begun wondering...how will we know if they come back next year, if this is the same pair, or a different one? I'm *terrible* at individual bird identification, even for large raptors (I'm much better at large mammalian predators, like wolves)...so do these small falcons have any unique *individual* markings that we could observe?

Here's a quick pic of our two...quite the couple, don't you think? I'm sitting her watching her sleeping soundly right now :) It's actually more entertaining than any "entertainment" on television!

Stephen H. Watson

Here's Blakeman's helpful response:


As it happens, I worked with probably a dozen or so American kestrels along with my red-tails in my undergraduate research on raptor caloric requirements at varying temps. I know the species well.

Each bird will be different, with unique feather patterns on the head and chest. Detailed close-up pictures of these can reveal individual IDs. But even as an experienced expert, this gets too far beyond tedious . Occasionally a bird will have a feather or two that is quickly diagnostic, but in most cases it's going to be lengthy periods of time comparing jpeg after jpeg. I don't recommend it. It's frustrating and ultimately confusing.

The far better approach --one that can really work -- is to get the eyasses banded. Check with the California wildlife authority, or a local US Fish and Wildlife Service office and ask for a raptor bander. Tell them the unique situation you have. Banding of eyass kestrels causes no problems. The adults are back feeding the young just about as soon as the bander closes the door on the nestbox. An ornithologist at any of the local universities should know of a bander.

You might ask the bander to apply colored bands, for easier ID. This may not be authorized by USFWS, as they prefer to do this only with important research birds but give it a try).

As always, I'm very interested in what the adults are feeding the eyasses. I have no idea what Pasadena kestrels feed their young. I presume insects are a notable fraction of the prey, but what mammals are being fed? I don't think you have the common vole (Microtus spp.) there. I may be wrong.

Keep me posted.


John A. Blakeman

PS: In the next communication, Watson informed Blakeman that the kestrels seemed to be eating mainly lizards.