While reviewing this month’s walk data, I came upon a resighted bird reported by Warren Mumford on his Cape Cod beach. The bird was nothing but a single wing and some gnawed bones, but still with a bright, shiny, aluminum tag affixed reading 588. I looked back through our records to determine when Warren first found and tagged 588, and was impressed to find that this bird has been on his beach almost a year, having been seen initially in March 2014. Here is a series of photos documenting 588’s decline:
First off, I can’t resist even a mini-DBQ, so, can you tell what species this is? Second, this case got me thinking about how we count dead birds and how to account for their persistence (or lack thereof) on beaches. As I begin analyzing data from the past two or three years, I am interested in looking at these tagged birds in particular. Once we instituted the numbered aluminum tags, how many of them were resighted on later surveys? How many were never seen again? How does this differ across beaches? And moreover, 588 shows us how long wings can stick around. Who knows how long dead 588 was when it turned up on Warren’s beach in the first place? How long can a set of wings and a sternum drift around before landing on a beach? And if wings can stick around for so long, are they really useful in trying to track mortality through time? If a set of wings might be from a bird that died a year previous, should it be counted, for instance, in an acute mortality event, or should only intact carcasses be used for that?
Lucky for me, there are actual trained scientists with trained scientific minds who can help me sort this out as I tackle the data. We shall see what it all yields.