Laura Catterton and I spent a couple of hours at the PW landfill today:
noon-2 pm.
There was no sign of any white-winged gulls.
We had two yellow-legged birds, other than Ring-billeds. One of these was a
'no-problem' adult Lesser Black-backed Gull. The other was fairly close to
the LBBG, allowing some comparisons. We are not sure what it was, so a
description follows. Anyone with views on it is asked to let me know, copy to
Laura - - thecattertons@xxxxxx.
The mystery bird was about the same size as a Herring Gull, perhaps a little
smaller. It appeared to be an adult, with bright yellow legs. The wings were
noticeably lighter than for the LBBG but darker than for Herring. I was
hoping for California Gull: unfortunately for that hope, the bird's eyes were
clearly pale, and I am not aware of any Californias without quite dark
irises.
Perhaps it was a Yellow-legged Gull, especially as our bird's bill did seem a
little shorter and a little deeper than for Herrings nearby. However, our
bird's head seemed too strongly streaked for YLG, never mind being too
widespread -- indeed, its head looked almost precisely marked like adjacent
adult Herrings. And we could not see any indication that our bird had a
'squarer' head, peaked at the rear of the crown -- again, it looked just like
the Herrings. So I tend to dismiss Yellow-legged Gull as well.
We have considered a yellow-legged form of Herring Gull, as the National
Geographic guide indicates that 'some smithsonianus Herring may show some
yellow during winter'. But the yellow on the legs of our bird was strong; and
the wings were too dark.
Another possibility is a lighter-winged form of Lesser Black-backed Gull, if
that exists relative to graellsii; but the head markings were much less
prominent than other US adult LBBGs (graellsii) we have seen. How variable
can LBBG be in terms of wing color and head markings?
Unfortunately, when the bird took off (and disappeared), it did so in a
general chaotic movement, and we were unable to add useful in-flight
description. Do we have to settle for yet another mystery gull?
PS. A little while ago, I posted a description of a 2nd-winter 'ring-billed'
type gull, with dark iris and gray legs. I 'guessed' this might be a
Ring-billed Gull, as the bill shape was more like that species than the Mew
Gull alternative, even though Sibley clearly shows pale iris and yellow legs
for 2nd-winter Ring-billed Gull and dark iris and gray legs for 2nd-winter
Mew Gull.
I was gratified to receive 3 thoughtful responses and subscribers might be
interested in a synopsis of what they said. While one respondent thought I
might have a Mew Gull, another suggested that I do give most importance to
the structural issue (bill shape) than coloration of iris and leg. On
coloration, Grant's guide to Gulls does state that 2nd-winter Ring-billeds
only 'usually' have pale eyes, with legs 'usually greenish-yellow, sometimes
yellowish, greenish-grey or gray,' thus allowing for my bird to be
Ring-billed. One respondent said that 'many' 2nd-winter Ring-billeds have
dark iris and gray legs, while another said that 'most' did so. CONCLUSION:
First, clearly my bird was a 2nd-winter Ring-billed Gull. Second, BEWARE
Sibley on this, which gives no clue concerning this variability.
Stephen Eccles
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