Kestrel Eggs Appearing in Ulster County


Yesterday was my day to make the rounds of the nest boxes and check for eggs. Since rain was forecasted for today (correctly) and I hadn't checked most boxes for about 10 days, I needed to see nest contents before clutches were complete, which typically takes 9 days. I was really hoping for eggs and was not disappointed. Five of the boxes had either one or two eggs. Here's what the inside of three boxes looked like yesterday: 









The female from the box with two eggs likely began laying, at the earliest, on 20 April. An average clutch is 5 eggs, so if she lays one egg every other day, her clutch should be complete around 29 April and her eggs should hatch sometime around 1 June (incubation takes about a month). Box checks with incomplete clutches are ideal, because now I know roughly when incubation will start and the eggs will hatch. If my first look at eggs was of a complete clutch, the female could have completed yesterday or a week ago...not ideal. I will estimate clutch completion dates for these boxes, and check again a few days later to confirm the final clutch size. All of this allows for a fairly precise estimate of hatching date. I will then check the boxes again about a week later to get a count of nestlings and estimate their age to determine when to return for banding...the really fun part. 

The news yesterday wasn't all rosy, as I found a couple of starling nests, with eggs, in boxes where kestrels were in residence only a few days prior. Starlings...grrrrrrr. These persistent, non-native birds are a serious competitor with kestrels for nest sites here in the northeastern US where open habitat and cavities are at a premium. 

But the kestrels are breeding, which is great news. There are pairs occupying a few of the new boxes I installed this year, which is encouraging. Hopefully these birds will establish breeding territories that will be occupied for years to come.  ¡Viva cernicalos!

Comments

Popular posts from this blog

Spring Weather, Chick Banding and some Fledglings

Hatching

Foreign Recovery, Clutch Sizes and Hatching Imminent