13 July 2013 – unknown passerine (scavenged)

Of the 138 casualties I have documented on this project there are just four I have not been able to confidently identify, most recently this feather I found Saturday morning:

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The feather appears to be an outer rectrix from a bird that collided with the building and was scavenged in less than 24hrs.  The rachis is dark on the upperside and whitish on the underside. The exterior edge of the vane is olive green without pattern.

The feather is the right size and shape to have come from assorted warblers, vireos, or other species.  I’m okay simply including it as an “unknown”.  There are other single-feather finds that I have been able to identify (e.g., cardinals); this one apparently not.

The feather, together with the ongoing scavenging rate trials a few meters from where it was found, illustrates well the difference between “scavenging” and “removal”.  The Northern Cardinal carcass that I found in June was not scavenged except by beetles, ants, and isopods.  Thus it was never removed from its final resting place.  Weeks later, a single rectrix remains of that bird.  I judged that one day last week I would’ve overlooked that feather in the course of my daily monitoring, so I estimated that it was in evidence for 26 days.  It’s actually still there, however, and I noticed it this morning.  I could keep counting it as “detectable”.  Either way though it illustrates the point:  I could have detected that feather at any point during the 26-day period that it was noticeable and I would have a record of that mortality even though the carcass had technically been scavenged.

With respect to the two buntings and the chickadee from last week, they’re still there even though all have been scavenged in situ:

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From top to bottom:  Carolina Chickadee, Indigo Bunting, and Painted Bunting.  All have been scavenged but none have been removed.  Traces of these birds might last for weeks, increasing my chances of detecting the casualty even if the bird has been scavenged.  What matters is whether or not the carcass has been removed.

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