3 June 2012 – Mourning Dove and Black-and-white Warbler

It’d been a few days since I had checked the Noble Research Center, and we’d had a few storms during that time.  June 1st was actually just a plain, old rainy day – very unusual.  Given the unusual weather, I figured there might be something waiting limply at the base of a window.  I did not, however, anticipate that it would be a resident bird:  an adult Mourning Dove:

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Given the state of decomposition on this bird, I will assume that it died at least one day ago.  It might have been longer, but I will consider for my analysis that it died on June 2nd.

Next, I was surprised by a window-killed Black-and-white Warbler.  This was a bedraggled and somewhat decomposed 2nd year female, and for my records I will also consider June 2nd as the date of death.  This is at least the second time that I’ve found a Black-and-white Warbler in June.  What to make of these birds?  It’s well past the normal spring migration for this species (March and April here in Oklahoma), and late enough that this movement could be post-breeding dispersal.

Here is a range map for Black-and-white Warbler:

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While they breed far to the north in Canada, they don’t even range into Alaska.  I wouldn’t be too surprised to find something that breeds way north like a Wilson’s Warbler at this time of year, given that some of its breeding range might just now be productive for breeding.  So it doesn’t make sense – at least to me – that there should be migrants streaming north this late in the season. 

Check this out though – frequency of Black-and-whites in eBird checklists:

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Well there it is.  You see two distinct peaks of the species appearing on checklists that obviously indicate spring and fall migration, respectively.  But where we might expect a steep drop in reports at the end of May, there’s actually a little bit of a bump in early June.  Now that could just be people finding them on territory where they breed, but it could also reflect movements of Black-and-whites that cause them to be detected in other places as well.  Given that we have found fully fledged Black-and-whites as early as 28 April, I’m suspicious that there is a bit of post-breeding dispersal that I might be experiencing with these window-killed birds in June.  Anyway, here’s the bird:

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