28 July 2015

July Lesser Black-backeds on the Cape Cod Peninsula

The frequency at which Lesser Black-backed Gulls are being seen along the Atlantic coast in the summer months continues to steadily increase. There are some sites where the species is locally abundant and is found in the hundreds (such as Chincoteague NWR in Maryland and Virginia). But at other sites, Lessers tend to be unpredictable, seen by the tens and even hundreds one week, and then all but non-existent the next week.
Some of this may be due to observer-bias, but also likely is a rapid turnover rate as the species moves out at sea or up and down the coast in search of a food source.

Similar to when I wrote about the status of LBBG in Birding magazine a few years ago, the age distributions are still consistently in favor of young birds - mostly 1-2 year-olds in the midst of complete molts. Rarely do I find evidence of definitive adults being recorded in the breeding season.

It seems to me, however, that a percentage of younger birds may be going unnoticed in Herring and Great Black-backed flocks, especially as one moves north into New England where the latter two species are found in greater numbers.

A mixed flock of Herrings, Great Black-backeds and Lesser Black-backeds. How many LBBGs do you see in this photo?
A not so uncommon summer sighting on the mid-north Atlantic coast, a Herring, Lesser Black-backed and Great Black-backed, all seen together. Provincetown, MA. 18 July 2015. 
Certainly a percentage of any species will go "unnoticed" without comprehensive counting efforts, but I feel it's especially true with immature Lesser Black-backeds in the summer months (see for example what I discovered on the Wisconsin lakefront a couple of summers ago).

Earlier this month I spent a total of 3 days surveying gulls at two sites along the northernmost point of the Cape Cod peninsula: Herring Cove & Race Point Beach in Barnstable County, Massachusetts. These two locations hold an impressive diversity of summer gulls, and one need not look any further than recent eBird reports to verify this. Surprisingly though, high counts of Lesser Black-backed Gulls reported at these sites in early July 2015, by reliable observers who regularly count birds at these locations, were 5 and 8, respectively. Below are my high counts.

High Counts:
Herring Cove. 18 July 2015. 27 Lesser Black-backed Gulls
(22 1st summer, 4 2nd summer, 1 3rd summer).

Race Point Beach. 19 July 2015. 39 Lesser Black-backed Gulls
(21 1st summer, 13 2nd summer, 3 3rd summer, 2 4th summer types).

I don't mean to be critical of the experienced birders that frequent these sites as I'm sure they're perfectly capable of identifying sub-adult Lesser Black-backeds. But as one birder put it to me, the attitude in the summer months is much like this: "I'll just add any gulls I didn't feel like looking at to the HERG count".

GBBG, HERG, GBBG, LBBG. Barnstable County, MA. 19 July 2015.
So in effect what may be happening with many birders is that they find a few LBBGs, check the species off for the day, and then proceed to not pick through larger gull flocks. In other words, they're not actively looking for Lessers but will count any obvious birds that are caught in their peripheral (I suspect this happens with other species from various families as well). In addition, certain sites are birded while stationary, and would there have been more miles put in surely more LBBGs would turn up in these day-list totals.

Advanced 2nd summer type LBBG, 4th summer type GBBG and 1st summer LBBG. 
4th summer GBBG (Appledore Island Black 9M0, born in 2012) and 1st summer LBBG.
1st summer LBBG and 1st summer GBBG.
First summer LBBG and GBBG
Two 3rd summer type LBBGs, one 1st summer type and an adult type HERG. The second bird from the left is big-billed, big-bodied and has noticeably pale upperparts. I do suspect it may be a LBBG x HERG hybrid (so called Appledore Gull).
Very similar in plumage aspects, these 1st summer cousins are readily told apart by size and structure.
Both this bird and the individual below appear to be 4th summer types, and not yet definitive adults.
Perhaps the maturest LBBG I've seen in July on the Atlantic coast. Barnstable County, MA. 19 July 2015.
Flight shot of the same individual pictured above. Secondary feather replacement nearly complete but it appears to be a "stepwise" molt. EDIT: THE OPEN WING ON THIS BIRD SUGGEST THE OUTERMOST PRIMARIES (P9-P10) ARE 2ND GENERATION. IT'S MORE LIKELY THIS IS AN ADVANCED 3RD SUMMER LBBG. THANKS TO MARS MUUSSE FOR THE USEFUL COMMENTS ON AGING THIS GULL.  
I've received several requests in the last few weeks about identifying first summer Lesser Black-backeds. Stay tuned for an upcoming post where I'll describe identifying this age group in its first plumage cycle.

And now the answer to the "number of LBBGs" from the photo in the beginning of this post:

A total of 8 LBBGs in this frame. Barnstable County, MA. 19 July 2015.

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