General Discussion : Kestrel biology/nestbox competition question

"Our" Kestrels (in Benicia, CA, in the San Francisco Bay Area) hatched around May 10th, and the adults have been regularly bringing food, etc. The chicks are now quite vocal, but are not yet peaking out of the box.

Earlier in the season there was competition for the box between two Kestrel pairs. I have not seen evidence of the second pair since well before the chicks hatched, but just now I saw two male Kestrels try to squeeze into the box at the same time and then fight each other. Does anyone have any comments/info about what might be going on? Will a second male kill this pair's chicks?

The Jessops


Sarah Schulwitz's picture

Interesting observation! I've heard anecdotes that kestrels may be "waiting in the wings" for an occupied box to become unoccupied. I have not read about or found any studies after a quick Google Scholar search of non-parental infantacide occuring in American Kestrels. I did, however, find a record of this behavior in another falcon species, Eleanor's Falcon, though it appears to be rare:

Thanks for your observations and questions! -Sarah

hollyjessop15's picture

This ended up being the last time that we saw an adult male come to our backyard Kestrel box (on 5/23/2017, when two males were seen trying to enter the box at the same time and then fighting each other) ... the chicks were about 17 days old at this point, I think. The adult female finished raising them, and they fledged on June 6, 2017. The chicks appeared to continue to do well after fledging, and were last seen in our backyard with their mother on June 20th.



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Posted in General Discussion by hollyjessop15 11 months 4 days ago.