13 October 2014

More Gull Specimens From Chicago's Field Museum

I again had the pleasure of looking through the gull collection at Chicago's Field Museum last Friday. The most interesting specimen studied during my visit was this first cycle bird:

Monterey County, CA. March 1909.
It was identified as a California Gull (L.californicus), but the bill's pattern and shape didn't seem consistent with that species. I also felt the lack of post-juvenile scapulars seemed wrong for a 1st cycle California Gull in March. Herring Gull crossed my mind but the uppertail coverts and outer tail edges didn't agree with Herring. I left the specimen alone and wasn't comfortable labeling it. Thanks to Steve Hampton and Tristan McKee - both gull aficionados from California - for steering me in the right direction on this one and suggesting "Western Gull" (which I fully agree with). Here are Tristan's comments regarding the scapulars:

"...looks just like a March Western. The small size is probably a preparation thing. My impression is that ALL the juvenile scaps have been replaced, as expected. Western's preformative molt is so early that the feathers come in quite young-looking".

Given that it was collected in Central California in March is another reason to believe it's indeed a Western.
The last few days have been very educational for me as several people have cautioned me on the condition of old specimens housed in museums. In particular, taxidermist Keith Mueller had many useful comments to make that were taken to heart:

"Be careful about relying on bill and tarsii measurements on any Taxidermy mount (unless an cast artificial head is used) especially very old skins whether full mounted or drawer skins. These dried skins can dry and shrivel so varied that it would be impossible to gauge the extent or the shrinkage and distortion, and for that matter, color fading. Even plumage coloration fading and handling wear can be completely different than the actual color values. I have been a Taxidermist since 1974 and have seen s o much variation in fading and distorted bare parts, actually this info is almost useless in relation to reality."

"Amar, the colors can do just about anything as the bill dries. I have seen a few lighten up, but mostly they get darker and often turn blotchy and uneven."

"A skin that is that old will be subject to quite a bit of degradation through time, especially if they are not cared for properly. Markings can change also when the feather texture degrades giving a false optic as to the actual shapes and forms of the markings. Evaluating study skins can be challenging with all these factors taken into consideration. The best approach I have found is to compare a drawer skin to an actual photograph and make your conclusion that way."

"When a skin is prepared for a drawer skin, how the "inside" of the skull is handled will also change the shape of the skull and bill. The concept behind drawer skins is to prepare the skin so it can be examined, referenced and researched for time."

It's becoming clearer to me that size measurements and bare part colors from old skins - perpared decades ago - are to be carefully considered, especially if no in-field experience is tied to these values. This makes the measurements taken from live birds (such as those found on gullresearch.org) much more meaningful. I wonder what implications this has on measurements found in the literature, specifically our gull guides.

Other interesting specimens from this visit include a leucistic 2nd cycle type Laughing Gull:

New Jersey. Early June.
The faded hood feathers are interesting - this might be a consequence of long-term feather deterioration exhibited by old skins, or a result of this bird's leucism. Notice the complete fading of the bill color! This is a clear example of a dark bare-part color becoming light, just as a light bare part color may become darker when housed over a long period of time.

There are lots of other interesting skins that I saw during this visit and I'll eventually get around to posting all or most of them with comments, but for now, I'll finish with a set of four folded wingtips, from darkest to lightest. Care to guess what species these are? The answers are posted below.

The two on the left were identified as Thayer's Gulls (Alaska and British Columbia) and the two on the right as Iceland Gulls (Nova Scotia). The third bird was actually collected by Earl Godfrey.

08 October 2014

Not A Most Wanted Poster, But...

I put this collage together, just for fun, knowing all of my gull-inclined readers would get a kick out of it.

The identities are intentionally left off, so feel free to give it a go and see if you can identify these individuals. They're all adults and they all occur in North America. Looking forward to your comments!

05 October 2014

A Note on Upperpart Color Variation in HY Ring-billed Gulls

I think it's fairly safe to say that adult Ring-billeds don't deviate from the Kodak Gray values that they've been assigned in the literature (KG value 4-5), but what about sub-adults, particularly hatch year birds?

Hatch Year Ring-billeds. Slightly darker scapulars shown by the individual on the left.
I'm most confident that post-juvenile scapulars on HY Ring-billeds do vary in color tones. I believe this to be primarily a result of these feathers not being "entirely" gray, showing a random mix of brown hues (on dark birds) and white hues (on pale birds).

Left bird shows slightly paler scapulars with whiter hues, while the individual on the right has browner hues.

These differences can be nearly impossible to detect under bright sunglight, and as always, observers should choose overcast days to accurately evaluate grays. Notice how the gulls in my photos aren't casting any shadows onto the ground - a good indication that the lighting is neutral, or mostly neutral.

The variation in upperpart "hues" on these two individuals should be noticeable.
Aside from gray, these post-juvenile scapulars show a mix of grown centers and white edges. These cololrs surely influence how the eye perceives the gray colors on HY birds.
A good example of a "pale" HY Ring-billed. This individual shows silvery-white hues on the post-juvenile scapulars. 

If it was later in the season, the pale gray on the individual above might be attributed to "bleaching", but being this early in the season, my guess is that there's actually very little bleaching - if any - that has affected these feathers. Further, it would seem that individuals with paler upperwing coverts would have paler scapulars, and individuals with more solidly brown upperwing coverts are more likley to show these darker scaps.

Perhaps this caveat also applies to other gull species - American Herring Gull being the first example that comes to mind. I've long suspected that sub-adult Herrings (3rd and 4th cycle types) can show slightly darker grays, and my explanation for this has long been that some of these birds show an excess amount of underlying brown tones within their gray feathers. More to come on this in an upcoming post...

04 October 2014

Three Herrings and a [Dead] Fish

It's not uncommon to find Herring Gulls feeding on dead fish along the Illinois, Lake Michigan lakefront, especially in the Fall season. Below is a series of photos taken at 63rd Street Beach on 01 Ocotober 2014.

When I arrived at the beach this adult was feeding:

Close by were two younger birds - a second cycle and a hatch year bird - patiently waiting their turn to feed. Somehow the HY bird snuck in after the adult, and this seemed to disobey any hierarchy-of-feeding code, if such a thing exists with gulls:
But not for long. The 2nd cycle almost instantly moved in and flexed its muscles:
They locked bills for about 30 seconds...
 ...a little tugging and splashing...
 ...and even an unfair wing-lock from the 2nd cycle...can you predict the victor?
The older and more experienced gull definitely won this short scuffle and proceeded to claim its booty:

A couple of comments on plumage features from this set: the adult type has relatively large p10 mirrors (p9 dropped here), but I've come to accept this as "variation at the species level" that's perfectly okay for individuals on southern Lake Michigan. Whether this is age-related or not remains unknown with American Smiths.

The 1st cycle has almost completely replaced all of its juvenile scapulars which is just a tad more advanced than what I've been seeing for the last couple of weeks in Michigan City and New Buffalo, but still, completely expected for this region.

The relatively large pale tips to the newly grown primaries on the 2nd cycle bird are the boldest they'll appear all season. Here's a better look at the open wing:

The white tips will soon start to wear down as the season progresses and will likely be unnoticeable by the end of winter.

29 September 2014

Hatch Year Franklin's: Carlyle, Illinois

We had at least 3 first cycle Franklin's Gulls following our boat on Saturday, 27 September 2014, on Carlyle Lake in southwest Illinois:

Note how the black tail band does not typically extend to the outer rectrices.

This species is very reliable at Carlyle in the Fall, and I'm beginning to get the feeling that hatch year birds are more common here than adults. For the last 4 years, every Franklin's I've seen on the lake has been a hatch year. Perhaps the adults don't partake in following boats and competing for "bread" and "popcorn"?? In general though, I think the majority of the adult population tends to keep west of the Mighty Mississipi River while on their southbound migration...

25 September 2014

First Cycle California Gulls

Below is a collection of 1st cycle California Gulls photographed in Half Moon Bay, California in mid-September. All are hatch year birds - some still in complete juvenile plumage while others showing early 1st alternate scapulars. Subspecies unknown.

(1) All juvenile scapulars, a few showing a holy-leaf pattern (a pattern that's been associated with Herrings). The mostly black bill is shown by a minority of birds in mid-September. Band information to follow.

(2) Still entirely juvenile. White forehead. Bill pattern with a mixture of black not uncommon for mid-Sept.

(3) "Cinnamon" type. Pale underparts and chest partially due to bleaching but also plumage variation. Post-ocular line.

(4) Cinnamon type still fully juvenile. Note the characteristic white forehead commonly shown by this age class.

(5) Similar to the individual above, but more black in the bill and some smoky gray 1st alternate scapulars.

(6) Smaller bird showing the famous decurved gape. Large, plain juvenile scapulars.
Size variation is difficult to appreciate in photos, but what is obvious from these images is the immense variation in upperpart patterns and coloration.

(7) A bigger and darker Herring-sized bird. A few dark gray alternate scapulars mixed in. Note the long-winged look.

(8) Moderate post-juvenile scapular molt. More typical plumage aspect. Blue-gray tibia can be shown at this age.

(9) Longish bill, straight and skinny, with typical two-toned pattern. Moderate scapular renewal. Neater lesser/median upperwing coverts.

(10) Large individual with larger bill and head proportions (male?).  Upperparts more worn than average.

(11) Small bill. Variegated look to upperarts becomes more common as the season progresses. Classic anchor pattern on the lower scapulars. Replaced upper tertial?

(12) Very plain greater and median coverts. Note the dark post-ocular line. Undertail coverts plainer than most Herrings.

(13) A darker cinnamon type with smoky gray post-juvenile scapulars. Matching some Western Gulls in size. Massive.

(14) Extensive post-juvenile scapular replacement. Variegated and dark-gray scapular centers advanced. A few renewed lesser upperwing coverts and a renewed greater upperwing covert. Undertail coverts generally not as neatly barred as Herring. Lower hindneck blotchy with a heavily greased look.

Overall, 1st cycle California Gulls have upperwing coverts that are weakly patterned and not as neatly shaped as similar-aged Herrings. Their bills are mostly straight with little expansion to the gonys. By early October the bill pattern is two-toned on almost all individuals, but some birds can exceptionally retain a mostly black bill into late October. On average, the species appears shorter and smaller than Herring but slimmer towards the rear with longer wings. 

22 September 2014

Banded 2nd Cycle American Herring

I found this banded 2nd cycle American Herring in New Buffalo, Michigan yesterday, 21 September 2014:

USFWS Band: 1106-27490

The Bird Banding Lab gave the following: Banded June 25, 2013 (too young to fly); NE Jack Island, Door County, Wisconsin.

Incidentally, this is my 4th banded HERG that I've found in New Buffalo that's been banded on Jack Island. Are a lot of these birds migrating straight south along/over Lake Michigan? Do they migrate together? Do they remain on southern Lake Michigan until they're ready to breed, or do they migrate back north in the Spring?

Map from Jack Island (WI) to New Buffalo (MI). Roughly 300 miles.

This individual shows rather typical 2nd basic primaries and secondaries. The underparts have a bit more dark wash than average, and the scapulars are not as advanced with gray as many similar-aged 2nd cycle Herrings. Also, the uppertail coverts are more barred than what I believe the average 2nd cycle shows. In many ways, this bird is less advanced than what I consider typical of 2nd cycle American Herrings.

One thing that I'm beginning to wonder about is if some (many?) of the presumed 2nd cycle Herrings that we readily age as such, may actually be less advanced 3rd cycles. Birds with mostly white uppertail coverts, mostly gray backs and adult-like inner primaries like this one:

Herring Gull (2nd/3rd? cycle). Whiting, Indiana. 04 Jan 2013.
Tertials mostly adult-like.
Inner primaries very advanced.
Peter Adriaens once commented on this bird and mentioned that similar-looking European Herrings, of known-age, showing these advanced inner primaries, almost always turn out to be 3rd cycle individuals. Could it be that many of our Herrings become definitive adults in 5 plumage cycles?

Here's another one I've wondered about - advanced gray scapulars and mantle, white uppertail coverts and semi-advanced inner primaries:

Chicago, IL. 26 Oct 2012. Advanced 2nd cycle or delayed 3rd cycle?

I'm hopeful that more data from banded American Herrings will help shed some light on this ageing question, in due time.

American Herring. New Buffalo, MI; 21 Sept 2014.

To read more about the other 3 banded Herrings (HY birds) from Door County, Wisconsin, that I previously found in New Buffalo, click here.