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Friday, April 13, 2007

Pale Pair

On Wednesday, I chased a young Glaucous Gull that Bill & Inez Prather found east of Longmont, Colorado at Saint Vrain State Park. Unfortunately, from the moment I stepped out the door of my bird-mobile I was subjected to cold, shrieking wind. Not ideal observing conditions, but when I found the bar where the gulls were hanging out I quickly spotted a big, pale bird. But then I thought I was seeing two such birds- did I have wind-induced, hypothermic double-vision? No, one was actually a little bigger (likely a male- unlike raptors where females typically are larger) and was a different age class. So in-between shivers and smashing gusts I figured out that there was one youngster (1st-cycle, I think) and a 3rd-cycle bird.
Bird quiz fans: ID the birds from left to right, including age... (I'll declare the cropped one on the right un-identifiable in this view.)
Now this was cool for several reasons. First of all, Glaucous Gulls are just sharp-looking gulls. Second of all, they are pretty rare in Colorado even in winter, but by April it is indeed an unusual sighting (although something odd is going on this spring with pale-winged gulls around here with an Iceland Gull last weekend in Loveland and a really pale Thayer's Gull down in Aurora yesterday & today.) Third, I've only seen singles previously in Colorado- never a pair together. And fourth, this is the first third-cycle GLGU I've seen.

I know that plenty of birders bail out on gulls, but they are missing out on a lot of fun (and a lot of cool birds.) You've got to think a lot when dealing with gulls. For example, why are 3rd-cycle gulls the hardest to find? Well, some gulls don't have a distinctive 3rd-cycle plumage, for starters. But among 4-year gulls, 1st-cycle birds and adults are the most commonly seen. Why? Adults can live a long time, and plenty of youngsters are produced every year. In fact, I suspect that a high percentage of vagrant or out-of-common-range gulls are 1st-cycle individuals who messed up their migration. Anyway, lots of young birds don't figure out the game of life and die before their 2nd plumage cycle. So there are lots fewer 2nd-cycle gulls than 1st-cycles. 2nd-cycle birds also fare worse than experienced adults, leaving even fewer 3rd-cycle individuals. If they make it to adulthood, though, they are much more likely to survive for many successive years.

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