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Tuesday, October 18, 2011

A good Kent Co tick, and not the age class I expected

Got a call from J Lau (aka Jonathan Lautenbach) yesterday morning which I knew was going to be a rare bird. Indeed, he reported 2 White-rumped Sandpipers at Millenium Park. This is a long-awaited county tick for me, so I shot down and was fortunate to find the birds with his help. First the location:

The birds frequented these 3 locations throughout our visit.
Here are the best photos I could manage of them:The big issue of course is not ID, but age. At this late date, i assumed theses birds would be automatic juveniles. However, I was struck by the lack of obvious juvenal markings on the tertials and wing coverts. Furthermore, when I got close looks, I realized that the terts and especially the wing coverts were heavily abraded. Juvenile White-rumpeds begin the preformative molt in November (Pyle Guide Part II), and even if they hadn't replaced their juvenal tertials and wing coverts by now they would be much much fresher and less abraded than those of this bird. Here is an example of a young bird from 19 Nov 2009 at Muskegon Wastewater. Note the juvenal patterning and broad, rounded edges (unabraded) of the already 5 month old juvenal terts and wing coverts.

So, I believe these two birds have to be adults. I would love to know when is "too late" for this age class at such a northerly latitude. I would expect adults to clear out of Michigan by mid September at the latest, but perhaps I need to rewrite my expectations. Thoughts on ageing and molt timing would be appreciated.

Kent co. tick 238! Looking forward to moving into the 240s sometime soon...


About this blog said...

Nice post. Very cool bird. Have White-rumped Sandpipers ever been found in Kent county? Thanks for posting.

Travis Mangione

Silly Putty said...

Travis- they surely occur annually or nearly annually, but detection and reporting are likely very limited. Here is the eBird map for Kent Co.:

It shows a series of sightings I hadn't heard about from June 2006. No idea about the accuracy of these sightings, but it is a plausible time of year to see them...