7–18 October 2017 – all kinds of stuff

I’ve been behind with stacks of papers to grade, and they’ve kept me from keeping up as often as I’d prefer. During the period from October 7–18, I conducted 8 surveys, skipping Oct. 8, 14, and 15. The data from these last 11 days look a bit like this:

  • Oct. 7: HOWR
  • Oct. 9: no casualties
  • Oct. 10: no casualties
  • Oct. 11: LISP
  • Oct. 12: TUTI
  • Oct. 13: no casualties
  • Oct. 16: OCWA, SOSP, LISP, and NAWA
  • Oct. 17: no casualties
  • Oct. 18: no casualties

Just past mid-October, and we are crushing the annual mortality count right now with 55 dead birds.

Oct. 7 – I found just the third House Wren on the project.  This one ended up on a warm air outflow grate from the air conditioning unit and was quickly desiccated.

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Oct. 11 – I collected this Lincoln’s Sparrow from the south portico.

Oct. 12 – This Tufted Titmouse was a surprise in the southwestern alcove.

Oct. 16 – This was not a good day for migrants. I found an Orange-crowned Warbler at the northeast alcove, a Song Sparrow at the south portico, and a Lincoln’s Sparrow at the southwestern alcove. Shortly after completing my survey, a Nashville Warbler was turned in from a collision in the southwestern alcove.

 

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9 August 2017 – 1.33 hummingbirds

Hummingbirds have been takin’ it in the shorts of late . . .

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But what’s with the fractional hummingbird reference above?  Well, “scavenging” and “removal” are not necessarily the same thing. Often I find the remains of a bird that has been scavenged, but there’s enough left behind that I am able to detect that a casualty has occurred. Those remnants – let’s say a pile of flight feathers left behind by a scavenging cat – can last in place for many weeks.  Each time I survey for casualties I’m greeted at that spot with the information that a bird died there (or at least somewhere nearby) even though all the edible bits are long gone. We should be clear that scavenging isn’t the important rate to help us better estimate detection of window-killed birds, removal is.  It’s only when every piece of that carcass is gone that I’m unable to detect the evidence of a casualty.

We see this played out all the time with hummingbirds.  For some reason, the ants seem to get to the hummingbirds more quickly than they get to other birds.  (I have some hypotheses about this, e.g., that hummingbirds are more often flying in daylight and might have lain in place longer than the night-flying warbler and sparrow migrants.) The result is that hummingbird carcasses are rarely in pristine shape when I find them, but they are still there.

Check out hummingbird #1 this morning from the southeast alcove.  First, look how obvious it is to detect the carcass even from ~20m away.  Up close, note that a good bit of her face has already been carted away, one ant-mandible-sized piece at a time.

 

 

This next one (or 0.33 of one) from the southwest alcove will put your observational skills to the test:

See it yet?

 

 

Oh, that explains it!

 

 

In this case, there’s a pre-scavenged hummingbird (likely also AHY-F Ruby-throated) that is represented by its tail only. But it’s still detectable and largely identifiable.

(UPDATE 10 AUGUST 2017: Today I found a head and wing near where I found the tail on Aug. 9. First, this looks much more likely as a HY-M than an AHY-F.  Also, literal scavenging seems less likely.  I suspect more that the carcass was chopped up by a lawnmower.)