An Immature Killdeer: Let’s Do the Math

In my last post on Bell’s Vireo I guessed at some dates in its breeding cycle. What really started my thought process on the Bell’s followed my initial reaction to the following photo:

And I am only going to post one photo today because I think the dialog is more important to this post.

KILL 052415A
The initial view of an adult and immature Killdeer which lead to this post. Johnson County Park. 5/24/15

After viewing the Bell’s Vireo, I came across an adult Killdeer that seemed to be making more of a raucous than usual.  Not giving the broken wing distraction, but loud and running around. I figured she had a nest somewhere in the loose, sandy gravel.  After searching for several minutes I finally saw why she was trying to divert my attention.

There was an immature Killdeer about three-fourths full-grown.

I was completely surprised and caught off-guard.

Many times I have seen recently fledged Killdeer. Those cut little balls that run around chasing their parents.  But that is always towards the end of June or early July in the warm, humid summer.

So by doing the math I found out that this immature Killdeer was either early or there was something I didn’t know.  And this lead to figuring the math on the Bell’s Vireo. 

As it turned out, I didn’t know the breeding cycle of the Killdeer. Since I usually see the downy young around July 4 I figured that they started nesting sometime around June 1.

But what I found out is Killdeer usually start the process much earlier.  Looking at the following chart you can see that I took the day I saw the Killdeer, May 23, and back figured the dates. Which means the adult Killdeer started working on the nest in late March, much earlier than I figured.

I learned it takes them approximately 8 days to build the nest, they usually lay four eggs over 6 days, it takes an average of 26 days to incubate the eggs, and the young leave the nest within one day of being born.  It takes somewhere around 30 days to almost reach full size, so I guessed this young one was around 20 days. Thus the nest start date of March 23. Not unusual but much earlier than I would have guessed.


Killdeer Days Date
started nest-building   3/23/15
nest-building 8 3/31/15
egg-laying 6 4/6/15
incubation 26 5/2/15
days in nest 1 5/3/15
young – days old out of nest 20 5/23/15

This also makes me wonder since she laid 4 eggs, what happened to the other young ones. Never hatched? Something got them when they were small? Already gone? And will this female try for another brood this year? Probably not since they usually only have one brood per year.

I previously had no idea of the breeding cycle of Killdeer. My complete lack of knowing once again shows how little I know about our local birds and that I don’t need to go very far to have an enlightening outing.

The information in this post came from The Birds of North America Online and The Birder’s Handbook – A Field Guide to The Natural History of North American Birds.

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