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Kestrels starting again before finishing what they’ve got?

If you been checking in on our American Kestrels you already know they had a successful nesting season.  The adult kestrels appear to have successfully fledged two female and two male young kestrels over the weekend, although one male remains in the nest box.  Hopefully, he takes his first flight soon and leaves his wooden prison (note: about 30 minutes after publishing this blog post, he bolted).  What came as a surprise over the weekend is the adults seem as though they can’t wait to get going on brood #2.   On Sunday, the female came into the nest box and laid an egg while the kestrel chicks were still in the nest box!   I thought one egg may just be an anomaly, but now there are two new eggs in the nestbox, as can be seen in the screenshot, below.

Kestrel chick and eggs
A view inside the Kestrel nestbox on 26 May shows two newly-laid eggs and the final remaining chick which is poised to leave the nest box at any moment.

I am not surprised the kestrels would, at some point during the summer, attempt to raise a second brood, but this behavior has perplexed me.  The adults still have to tend to the fledged youngsters for up to two weeks before they can fend for themselves.  Thus, laying eggs this quickly seems premature if these birds are indeed attempting to raise another brood.  An alternative explanation is that these eggs developed and they needed to be laid, but they are infertile.  The female returned instinctually to the place where eggs are laid.   With that said, it will be interesting to see if the adult female lays any more eggs and then if she starts incubating them right away.

We have observed successful double-brooding in our nest box in two other seasons, including last year. As wrote in an earlier posts, American Kestrels do not typically lay a second clutch of eggs or raise a second brood.  According to the Birds of North America (BNA) species account, only 11% of American Kestrels in Florida raised a second brood.   The BNA account also noted a “second brood less likely with increasing latitude.”  Based on this information, one might conclude a double-brooding is a rare event in Nebraska, but we keep producing data in our nest box to the contrary.  And no, we do not know if these are the “same” adults as previous years since the kestrels are unbanded.  However, it is not an unreasonable suspicion to think we are dealing with the same prolific pair over the past several years.  This is just more falcon drama.

Good birding!

Nongame Bird Blog

About Joel Jorgensen

Joel Jorgensen is a Nebraska native and he has been interested in birds just about as long as he has been breathing. He has been NGPC’s Nongame Bird Program Manager for eight years and he works on a array of monitoring, research, regulatory and conservation issues. Nongame birds are the 400 or so species that are not hunted and include the Whooping Crane, Least Tern, Piping Plover, Bald Eagle, and Peregrine Falcon. When not working, he enjoys birding.

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