14 December 2014

Black-backeds & White-wingers



I smelled trouble stirring early last week when I read the weekend forecast calling for upper 40-degree temperatures in the Chicago area. Both Saturday and Sunday made it above 50F, with a high of 54 degrees recorded on southern Lake Michigan today (14 Dec 2014). To top it off, overcast skies dominated all of Saturday and most of the day Sunday.

Despite a notable absence of gulls at some of our better gull-watching sites, I still managed to see all five of our winter species with a bit of effort!

Saturday: 13 Dec 2014; Rainbow Beach, Chicago, IL.

GBBG (adult type).
GBBG (adult type).
LBBG (2nd cycle type).
LBBG (2nd cycle).
LBBG (2nd cycle) with Ring-billed (adult) and Herring (1st cycle).
Sunday: 14 Dec 2014; Whiting, IN.


GLGU (2nd cycle).
GLGU (2nd cycle) with adult type Herring.
GLGU (2nd cycle).
GLGU (2nd cycle).
GLGU (2nd cycle) with HERGs.
A heavy-billed, dusky-eyed 3rd/4th cycle type Thayer's Gull.
THGU (3rd/4th cycle type).
Thayer's (3rd/4th cycle type) on far left, with 3 Herrings on right.
THGU (3rd/4th cycle type) with similar-aged HERG (right) and adult type HERG (left).
A shot of both the sub-adult Thayer's and the Glaucous in one frame...not the best photo, but it captures the day's highlights for me:


Here's a nice hatch year Ring-billed to conclude this post. Note how well it's holding on to its juvenile flank, chest and neck feathers. Most similar-aged RBGU's have for some time now shown mostly whitish feathers here, with variable streaking on the head and hindneck that's not as extensive as this:

 RBGU (1st cycle).

RBGU (1st cycle).

11 December 2014

Glaucous & Iceland Day

It's not often that I hit my exact target(s) for the day, but I left my house in the morning saying to myself "I need Glacuous and an Iceland today". The day was a success!

Glaucous Gull (1st cycle). Lake County, IL. 04 Dec 2014.
Notice how the lowered tertials and empty crop (pre-feeding) make this bird look sleeker and somewhat thin. It wasn't a very big GLGU to begin with - not much larger than many of the male type Herrings.
Glaucous is always a long shot at the Fairgrounds and this is only my 5th one for that site.

Adult Icelands are always a treat too, especially when their identity is not clouded by darker, thayeri-like primaries :

Kumlien's Iceland Gull (adult) with similar-aged Herring. Lake County, IL. 04 Dec 2014.
It may take some squinting and stepping back from your monitor, but the tonal values to the upperparts of the Iceland do strike me as being lower than the Herring's. The wingtips of this bird somewhat resemble the Hammond Indiana Kumlien's.

All in all though, the Lake County Fairgrounds had substantially lower numbers this first weekend of December, in comparison to the great end to November. This goes against my prediction of gulls packing the arena after Turkey Day...maybe they were present but glued to the landfill. Temperatures were about 15 degrees warmer and in my experience, this almost never helps the cause.

04 December 2014

Banded Juvenile California Gull

A very exciting part of gull-watching for me is finding banded individuals and retreiving their histories from the Bird Banding Lab. I've reported quite a few birds in the last two years, and have had so many conversations on the phone with the lab, that some of the employees there have come to personally know me as the "gull guy". What a legacy.

Anyway, here's another one to add to the collection:

California Gull (juvenile). Half Moon Bay, California. 12 September 2014.
I entered this bird into the system the same day of the sighting, but just heard back from the lab yesterday:


It's not unusual for the database to be missing data on juveniles, particularly because of banders who haven't submitted their logs (it's a lot of data). The other reason one might get a delayed response from the lab is if the band is very old and predates some of the electronic records (rarely a problem).

In any case, back to the juvenile California Gull. It originates from Mono Lake - one of the biggest California Gull colonies in the United States. Notice the bird has retained a mostly black bill in mid-September, and there are no post-juvenile scapulars grown in yet:

Mostly black bill and juvenile scapulars (slightly late hatch?).
Also note the cinnamon tones to the breast, neck and loral region.
Compare the juvenile above to this hatch year CAGU:

Mostly all of the juvenile scapulars have been replaced and the bill has taken on the classic "bi-colored" pattern that 1st cycle California Gulls are readily identified by. In addition, a few lesser upperwing coverts as well as a single, inner, greater covert have been replaced (the latter perhaps adventitiously).  
Is it likely this individual fledged well before the subject bird? Surely it must have taken some time to acquire all of these post-juvenile scaps (PF/PA1?). A similar thing occurs with our early Fall Ring-billeds here on Lake Michigan. A cohort of hatch year RBGUs on the same beach can have scapulars that range from entirely juvenile to almost all adult-like gray. I've for some time now believed they have to have different hatch/fledge dates.

Off to the next one.

02 December 2014

Cook-Inlet or Thayer's Gull?

I found this first cycle gull in Lake County, Illinois on Friday (28 Nov 2014):

Cook-Inlet (Herring x Glaucous-winged) or Thayer's?
My initial identification was "heavy set" Thayer's, partly because that's what "dark" white-winged gulls default to here, but the more I looked at it, the more I began to wonder. Adam Sell was present at the time, and after pointing the bird out to him, I commented on the semi-muddied look to the scapulars and how they seemed odd.

Jizz-wise, this bird stacked up equally to most of the Herrings around it. Not your run-of-the-mill juvenile Thayer's, although the bill size and structure seemed fine for THGU.
Martin Reid questioned the darker bases to the upperwing coverts and the seemingly short primary projection. This was the motivation I needed to think a bit more about the reservations I had in the field.

Broad arm, dark uppertail coverts and solid, dark tailband seem untraditional for Thayer's.

Barrel body, broad wings and larger head are very reminiscent of Glaucous-winged.
Another thing that bothered me during my observation was what sometimes seemed like an oddly high-placed eye.

It's amazing how a slight change in posture can give a longer look to the primary projection, but the eye-to-face look now appears like a classic Glaucous-winged hybrid.
Notice in the photo above (slightly overexposed) that the bill base looks like it's paling, and it actually was - another strike against a November, 1st cycle Thayer's.

Dark uppertail coverts with wide, solid, distal band. The proximal scapulars look solid brown and not the neatly patterned look I'm used to seeing on 1st cycle Thayer's. This, along with the dark-based upperwing coverts, and darker outer webs to the inner primaries all look like they've been influenced by Herring.
So the final verdict on this one is Cook-Inlet Gull...not the first one I've seen in Illinois and probably not the last!

30 November 2014

Second Cycle Kumlien's Gull

Here in the Western Great Lakes region, many Kumlien's & Thayer's could be suspected of being one or the other. You see, the two have a suite of characteristics that can - and do - overlap in every possible respect. Of course this is not to say that there aren't any clear-cut Kumlien's or clear-cut Thayer's here. There are.

But we also have many birds that take on a "range bias" when they're looked at by outsiders. Thus, the majority of gull enthusiasts on Lake Superior and Lake Michigan are left having to make arbitrary identifications with some of these birds. Fortunately, 2nd cycles are not as difficult as 1st cycles and adults.

Consider this 2nd cycle:
Dark Kumlien's or pale Thayer's? Lake County, IL. 28 November 2014.
I circulated the photos of this bird to several trusted gull aficionados from both regions of the continent (West and East coasts), and as expected, some birders from Colorado and areas to the west, identified it as a pale Thayer's, while birders from New York and east called it a Kumlien's. I favor the latter identification.

Rather plain outer primaries and overall pallid upperparts seem fine for Kumlien's Gull. 
One of the comments made by a birder from the western United States was that the tertials show solid pigmentation throughout and that this ought to support a Thayer's ID. I think that's generally true, but the caveat is that the tertials need to be considered in conjunction with the primaries and upperwing coverts. That is, the tertials on Thayer's tend to be a bit paler than the primaries, which are ideally a darker brown than is seen on this bird. Here's my idea of a "no gimmick" 2nd cycle Thayer's:

Thayer's Gull (2nd cycle). Santa Cruz, California. 17 January 2014.
Thayer's Gull (2nd cycle). Lake County, Illinois. 31 January 2014.
Notice how the tertials act as a color-bridge between the noticeably darker primaries and somewhat paler upperwing coverts.

It would be nice if all of our 2nd cycle Kumlien's were as obvious as the bird pictured below:

Kumlien's Gull (2nd cycle). Lake County, Illinois. 31 January 2014.
Or even this one:
Kumlien's Gull (2nd cycle). Niagara River. New York. 29 December 2012.
But some do have dark, solid-colored, tertials. Here are a couple from the Eastern Great Lakes that would never be second guessed as Kumlien's:

Kumlien's Gull (2nd cycle). Toronto, Ontario. 27 December 2012. Overall solid dark tertails centers, but with lots of internal markings and stippled upperwing coverts. The primaries are not as dark as I'd like to see on a textbook Thayer's. 
Kumlien's Gull (2nd cycle). Toronto, Ontario. 27 December 2012. Very similar to the subject bird. The lack of contrast between the solid tertial centers and pale primaries is standard Kumlien's.
Same bird pictured above. The outer primaries don't contrast much with the rest of the upperparts.
Consider the difference when a classic, 2nd cycle Thayer's opens its wing:

Thayer's Gull (2nd cycle). Michigan City, Indiana. 27 November 2014. The outer 5-6 primaries are markedly darker than the rest of the flight feathers and upperwing.
Thayer's Gull (2nd cycle with adult Lesser). Michigan City, Indiana. 28 November 2014. Although the tertials show pale outer halves, the bases have a solid brown color that's complemented by considerably dark brown primaries.
The take-away from this post should be that 2nd cycle Kumlien's with solid tertial centers are not uncommon, and the key is not to look at this field mark in isolation (as is the case with any field mark). Always compare the tertials to the color intensity of the primaries, along with the overall color of the upperparts.

16 November 2014

A Tale of Two Thayer's

I made my first visit of the season to the Lake County Fairgrounds on Saturday. I was happy to find the gulls comfortable and resting as they should be. I tallied 6 Thayer's Gulls for the day (3 adults, 1 fourth cycle type and 2 first cycles). Highlights were the 2 first cycles on opposite sides of the color spectrum - one dark individual and one light - which the title of this post is referring to.

Thayer's Gull (1st cycle). Hampton Scale Score 28.

Thayer's Gull (1st cycle). Hampton Scale Score 21.
The lighter Thayer's falls squarely between a solid Kumlien's and Thayer's, and so it wouldn't be unreasonable to call this a Kumlien's/Thayer's type, or KT (for a review of these scores, click here).




Although given the relatively dark outer primaries, along with the darker tertials and darker secondary bar, I'm leaning heavily towards Thayer's.

It's always fun seeing definitive adult Thayer's, but finding a near adult is much more exciting. Here's an open wing with plumage features that are suggestive of a 4th cycle "type":

Note the less advanced wingtip pattern. For instance, the mirror on P10 is faint and smaller than that on P9. Also seen is relatively extensive black streaking on the alula and outer greater primary coverts. 

The upper tail shows black markings and the upperparts are tainted with brown tones - both sub-adult features.
The prebasic molt is finishing up with the inner secondaries and the outermost primary (still about 1" from fully grown).
Lesser Black-backed Gulls are the 4th most common species here (with Herring, Ring-billed, and Thayer's being the other three, in that respective order). Here's an individual that appears to be a 1st cycle Lesser Black-backed. I never did get to see the open wing and so I'll have to think about it a bit more:

Possible LBBG. It's my hope that observers aren't looking the other way when they see these brown types with paler bill bases. I've learned that using the descriptions in field guides, and not allowing for variation at the species level, hampers one's ability to really get to know a species. Large gulls can not be contained by a field guide. 
Of all the species I see here in Northern Illinois, adult type LBBGs are always in heaviest, and latest, flight-feather molt. Even more interesting is that birds at this landfill, in particular, seem to be farther behind in their PB molts than those near the lakefront in Michigan City and New Buffalo (data is insignificant, based on 3 years of observations). Could it be that birds under higher demands of molt-stress resort to a more reliable and "convenient" food source, such as landfills? Whereas others with mostly grown flight feathers may be more inclined to fly out on Lake Michigan and keep to a more aquatic diet?




Miscellaneous Notes:

A 1st cycle Herring with a paling iris. This is not something I often see. Same individual above. 
Herring Gull (1st cycle). Not uncommon is this bill color aberration found on 1st cycle HERGs.
These darker brown Herrings appear to be more common out West. Birds this uniform likely originate from farther north (or away) from the general Great Lakes region.
Many adult type HERGs are growing out their outermost primary right now which gives those birds with a larger mirror on P10 a thayeri feel.  Couple that with the large, fresh, apicals and I had to stop to closely examine these birds a few times yesterday - especially on a couple that had darker, amber-brown eyes.
Thayer's Gull (adult type). Outer two primaries still growing.
One of my most interesting Herring types of the day was this bird:

Herring Gull (2nd cycle).
The mostly black bill and white rounded head give it an interesting look. The pointed brown centers to the newly grown scapulars and long-winged look had me wondering if there was something else going on here. More to come on this bird in my next post!