Wednesday, February 22, 2012

Thayer's week ! : Difficult adolescents

Thayer's week, day three.

Yesterday I talked a bit about how we can really only guess to the evolution of a Thayer's Gull's plumage as it gets older each year. But on top of that, I would like to take a look at how maybe the specific age of a bird can mess things up (and we may never know).

To help with the feature, another recent Waterloo Thayer's. This time, a bird in 2nd basic (2nd winter) plumage:

typical dark (but paler wings/tail/overall plumage than Herring gull) look... 

bigger/meaner look that many Kumliens

nice dark tail 

The flight shots aren't as pretty as some of the others, but I'll just use this bird as an example. I find myself seeing a LOT of 2nd winter Thayer's Gulls. Almost more than adults I think... And it got me thinking. What if the immaturity of these birds makes them darker? Many young gulls are darker than their adult plumages... Just look at our common Ring-billed Gulls in 2nd winter - almost all have darker wing tips (with more extensive black) than adults! 

Here's an old pic of a 3rd basic Thayer's: 

This bird as MEGA dark markings in the wingtips, but aside from that, doesn't look all that bad for Kumlien's. WHAT IF, next year (or 2 years down the road) the bird has lost 30/40% of the markings? Suddenly the hardcore gull watchers are saying the "adult" is a Kumlien's until proven otherwise? 

Old pic. 3rd basic Thayer's on left, 3rd basic Kumlien's on right.. 

Obviously this is rampant speculation on my part, but would be really interesting to know if (and how much) the wingtip pattern would change between ages 3 and 5+ ... As the above picture shows, we can still be fairly confident in telling these ages apart, since there are still many fairly obvious birds...

Oh Thayer's Gulls... You're so much fun. More on deck for tomorrow! (and it's a really sweet bird). 

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