7 replies to this topic

[Coastie]

Cape Cod. Apr 7


bn 065 by Coastie32, on Flickr



bn 067 by Coastie32, on Flickr

[Joejr14]

An adult and juvie Great Black-backed Gull.

[Grandpa577]

IMHO, based on the scapular pattern the second gull is a first winter Herring Gull. Great Black-backed Gull have a mottled black scapular pattern in the first winter and by second winter the black is more solid color. A second winter Herring would also be developing solid coloring in the scapulars but it would be grey. Because the head is so bleached white it looks more like a great Black-backed Gull than a typical Herring Gull, but the pattern and color of the undertail coverts, belly and greater coverts has the appearance typical of a Herring Gull.

[JimBob]

All I can say is that the first one is a GBBG.

[Joejr14]

IMHO, based on the scapular pattern the second gull is a first winter Herring Gull. Great Black-backed Gull have a mottled black scapular pattern in the first winter and by second winter the black is more solid color. A second winter Herring would also be developing solid coloring in the scapulars but it would be grey. Because the head is so bleached white it looks more like a great Black-backed Gull than a typical Herring Gull, but the pattern and color of the undertail coverts, belly and greater coverts has the appearance typical of a Herring Gull.

Hmmmm. Looks like I might have looked at the picture a little too closely. I have some problems with Herring, though. First, by this point this would be a 1st summer Herring (nit-picking, I know), because a 1st winter bird would be WAY darker, and should have a solid dark bill. While I agree on most of your points on coverts and belly, I disagree that head is bleached. The whites in the picture aren't blown, so are we assuming that they're just very worn? Additionally, I know all individualds in gull species can be highly variable, but this bird appears to have a HUGE bill...perhaps it's just due to angle? It also seems a bit odd to me that this bird appears to be exhibiting 1st summer traits, while still having mostly black primaries?

Shrugs. I'd agree more Herring than GBB....what about a cross?

[Grandpa577]

Hmmmm. Looks like I might have looked at the picture a little too closely. I have some problems with Herring, though. First, by this point this would be a 1st summer Herring (nit-picking, I know), because a 1st winter bird would be WAY darker, and should have a solid dark bill. While I agree on most of your points on coverts and belly, I disagree that head is bleached. The whites in the picture aren't blown, so are we assuming that they're just very worn? Additionally, I know all individualds in gull species can be highly variable, but this bird appears to have a HUGE bill...perhaps it's just due to angle? It also seems a bit odd to me that this bird appears to be exhibiting 1st summer traits, while still having mostly black primaries?

Shrugs. I'd agree more Herring than GBB....what about a cross?

The molt cycles and winter/summer designation seem so inadequate to explain how a gull should appear at a particular time in its life. For example, Sibley defines 1st Winter (Sep-Apr) and 1st Summer (Apr-Aug). The second molt cycle begins with the start of the second prebasic molt in "Apr" of the bird's first year and the molt can last until August or beyond when the second prealternate molt begins. The difference in appearance between Mar and Apr is due to bleaching and feather wear, predominantly and yet the bird is in different classifications. The confusion is further compounded by suggesting that a bird on Apr 1st of its first year (first summer) will look the same as the same bird six months later (still first summer) after a complete prebasic molt and the effects of summer seems to me a bit of a stretch.

This bird could be a GBBG or a hybrid, I can't know for sure. I do have reasons why I think it is a first year Herring Gull in April. The bill size: My experience is that the Herring Gull bill size can vary significantly much of it is explained away by the presumed sex of the bird with females having the smaller build and bill. I believe it appears longer than a GBBG while the GBBG bill is thicker and stouter looking. Also for a bird under one year of age the GBBG bill is in most, if not all cases, black. For example:


Great_Black-backed_Gull_9239f - Copy by Grandpa577, on Flickr

I believe the following picture, also taken on March 3, is of a GBBG, a year older.


Great_Black-backed_Gull_9244l by Grandpa577, on Flickr

The pattern of the undertail coverts and the bill shape and color don't seem to me to be consistent with the OP's second bird.

As for the darkness of the first winter HEGU, I couldn't have agreed with you more until two weeks ago when a flock of HEGU in migration stopped for a few days at the jetty at Jones Beach. The extent of paleness in these birds was way beyond anything I had seen on the HEGU that winter here. Some of it was bleaching, but I would guess some of it must have been a result of nutrition/diet. There were primaries the color of light cocoa.

[ColoTomo]

Good discussion on this thread. One thing I haven't seen brought up is the iris color on the second bird. It is strikingly pale. I haven't seen an adult GBBG with an iris this pale, much less one that I presume is being stated to be between 2nd and 3rd cycle. I'm not saying that I agree with Herring, but that's what I'm leaning to on the second bird. My initial impression the first time I saw this thread before Grandpa's response was Herring-but instead thinking more of a 2nd to 3rd cycle transition for Herring (based on bill+eye+scaps)... I'm not calling it a HEGU, but don't feel comfortable calling it GBBG

Would be nice to have Aberrant's input on this one !!! Who's the best at summoning Aberrant?

[Grandpa577]

I agree with you, Tom, the eye color is another factor. As for its age, without a clear view of the condition of the scapulars, I have a hard time discerning whether the pattern is fresh or worn.

I saw the following bird today and thought it was very similar to the OP's, (perhaps not quite as bleached out). On this bird you can see the solid grey scapulars coming in and that the PA1 molt scapulars with the brown centers are very worn which would lead me to believe this is a second year bird. The problem I have with this is that most second year birds in winter develop the gray mantle and scapulars as a result of PA2 molt. (According to Howell and Dunn, HEGU PB2 molt begins Apr-May late and PB3 molt begins May/June while adults PB molt begin in June/July (presumably just after breeding)

Herring_Gull_3303m by Grandpa577, on Flickr