31 March 2012

Pink Coloration in Gulls

The pink suffusion found on some gulls is considerably different than known color abnormalities such as albinism, leucism and melanism. This pink flush is said to be diet-related and is not permanent, changing in intensity from season to season, and sometimes within the same plumage (McGraw, Hardy 2005). At least 13 species of gulls are known to show this pink coloration to varying degrees. Some species rarely or never show it, whereas a few, such as Ross's and Franklin's, almost always show some trace of pink.

Adult Ross's Gull showing obvious pink tones on underparts . Cherry Creek Reservoir, CO. 21 NOV 2010.

The earlier literature suggested that this pink coloration was a result of red preen oil containing carotenoids that were applied to the feathers via preening (Stegmann, 1956). Grant also used this explanation in his identification guide but this explanation overlooks the fact that some white-headed gulls (such as Ring-billeds) show this coloration on parts of the head that are impossible to reach with the bill while preening.

Adult Ring-billed showing uniform pink coloration all throughout. Tinley Park, IL. 11 March 2012.
It's now thought that the carotenoid "astaxanthin" is responsible for the pink feathers we see in gulls (McGraw, Hardy 2005). What isn't very clear is why some individuals within the same species or same population show these pink suffusions and some don't. It's thought that some may have "sufficient access" to or "sufficiently utilize" these carotenoids. That is, some individuals find food sources that provide sufficient amounts of astaxanthin, or, physiologically, some individuals are able to accumulate and/or produce this carotenoid.

1st Summer Little Gull. Sheboygan, WI. May 2013.
As a rule, the smaller tern-like gulls are much more likely to display pink hues than the larger gulls.

Adult Little Gull with pink cast on underparts. Carlyle Lake, IL. 21 January 2012. Photo courtesy of Dan Kassebaum.

Most interesting is Hardy's suggestion that as of 1998, more and more Ring-billeds (up to 30%) in the Pacific Northwest have been found with traces of pink in their plumes. This was two years after salmon hatcheries in Washington state began providing synthetic astaxanthin as a diet supplement to their young fish. A natural question I've asked is why Mew and Glaucous-winged Gulls don't show these pink tones. I don't know of any gull species that consumes more salmon than Glaucous-wingeds - this species thrives on the spawning streams of salmon all throughout the Pacific Northwest. Could it be Glaucous-wingeds (and Mews) don't sufficiently accumulate, utilize and/or produce these carotenoids?

Observing this pink suffusion in the field is not very difficult, but it can be tricky. Overcast conditions are most favorable for observing and photographing pink gulls. Strong sunlight significantly washes out these pink tones. Take for example this Franklin's Gull:

2nd cycle FRGU. Chicago, IL. 25 March 2011.
When I first found this individual standing by itself on the beach, the deep pink hues were what first caught my attention. When it got up and began flying, the overexposed pink on the underparts was almost instantly diminished.

As for the implications this pink coloration has within conspecifics, McGraw and Hardy suggest the following, "Because carotenoid colors often are sexually selected indicators of mate quality in adult birds, there may be signaling benefits to producing pink plumage in these gull species". Although this may hold with Ross's and Franklin's Gulls, I've found that Ring-billeds with pink tones are at the bottom of the feeding hierarchy and they seem to be slight social outcasts among their flocks.

White and "pink" adult Ring-billeds. Oak Forest, IL. 27 March 2012. 

These "pink" individuals almost always seem to be more dirty and untidy, giving me the impression that it's difficult to remove dirt from their feathers via bathing and preening. Do these feathers possess an adhesive-like property? That would indeed be disadvantageous to any bird. Tentatively, I suspect the pink found on Ring-billeds, at least outwardly, is sufficiently "different" than what is observed on Ross's and Franklin's.

"Pink" adult Ring-billed. Chicago, IL. 24 April 2010.

What happened to the bird in the back? 
I would add that these "pink" Ring-billeds appear most intense at the onset of the breeding season and almost never in the winter season. This has also been my experience with Franklin's Gull. Is it possible that the carotenoid "astaxanthin" is hormonally induced?

Carolyn Marsh and I were recently discussing the increase in Ring-billeds exhibiting an exaggerated amount of pink feathers and she feels a steel factory in East Chicago, where now sits the largest Ring-billed colony on southern Lake Michigan, might be the cause. Her unverified thoughts on this is that some type of iron deposit or chemical is acting as an external dye in the water. I have a very strong impression that these birds have been subjected to ore dust that they nest near.

Calumet Park. Chicago, IL; 14 April 2012.

Although more is known about this colorant now than just one decade ago, there are still many questions that remain to be answered. I'd appreciate learning about your experiences and observations with these "pink" gulls.

05 March 2012

Same Gulls, Different Year

There's something comforting in having reoccuring birds return to our birding haunts. I went out on Sunday, 04 March 2012, to watch gulls on the Chicago lakefront. I started at Calumet Park and was treated to great looks at this hooded larid:
Presumed adult Laughing x Ring-billed hybrid. Chicago, IL. 04 March 2012.

This gull is believed to be a returning adult that has frequented the Lake Calumet area for the last 9 years! Amazingly, it always seems to move in with our first wave of returning Ring-billeds. Where it spends its winters is a mystery, but it goes absent around mid-November and reappears around early-mid March. Needless to say, I was ecstatic when it made its first pass along the pier:

I hit Hammond Marina next with Kumlien's Iceland Gull as my target. Within a few minutes of chumming, this adult Kumlien's came charging through the Ring-billeds:

Adult Kumlien's Iceland Gull. Hammond, IN. 04 March 2012.
I thought for sure this one was half-way north to its breeding grounds by now considering the mild winter we've had, but it was still halfheartedly clinging to its winter grounds. I should mention that this bird holds a strict winter territory unlike any other wintering gull I've seen.

For at least the last 4 winters, it's returned to the same perch at the harbor mouth, escorting out intruding gulls with a less than gentle attitude. One thing it doesn't often do is put down on the north side of the harbor, but today it allowed great views, perching for about a minute that went too fast!

My last stop was the BP Refinery in Whiting. As expected, Great Black-backeds were present on the beach (adult, 3rd cycle and 2nd cycle), but had no interest in coming in. Aside from several adult Herrings picking at a dead fish on the beach, there wasn't much to be seen here.

2nd cycle Great Black-backed. Whiting, IN. 04 March 2012.
3rd cycle Great Black-backed. Whiting, IN. 04 March 2012.
Here are some other gull photos for the day:

1st cycle Herring Gull. Whting, IN. 04 March 2012.
2nd cycle American Herring Gull. Hammond, IN. 04 March 2012.

Presumed Laughing x Ring-billed hybrid. Chicago, IL. 04 March 2012.

Adult Ring-billed with dark iris. Chicago, IL. 04 March 2012.

02 March 2012

Gull Sit 2012

On Sunday, 26 February 2012, a few birders and I conducted a "Gull Sit" at North Point Marina (Lake County, IL) in an effort to count gulls! Winds were primarily from the south all day at 17-30 mph and temperatures ranged from 26F-48F. Approximately 70% of the harbor was ice-free. The harbor south of the yacht club was monitored continuously from 7:00 a.m. through 5:30 p.m with some interesting results.

First cycle Thayer's Gull. NPM, IL. 26 FEB 2012.
The day's high for "stationary" gulls was approximately 1,150 individuals (~ 970 American Herrings, ~ 180 Ring-billeds). This maximum was reached in the last 90 minutes of daylight, while average numbers throughout the day hovered at or around 800 (over 85% consisting of Herrings).

No "mass exodus" was observed at any one point throughout the day, but rather, 2-3 small groups of 75-100 gulls were noted flying westward early in the morning (very likely to the Zion landfill). Returning numbers from the west consisted of small, loose, groups throughout most of the day. There were two instances when ALL of the gulls got up and were reshuffled, once because of a low-flying helicopter and once because of a Snowy Owl that came in directly over the harbor from south to north. This Snowy was markedly whiter than last week's bird.

Hourly counts verified a constant flow of gulls coming and going, which was expected. For instance, between the hours of 7- 11 a.m., at least 4 adult Lesser Black-backeds were noted, but not one was to be seen again for the entire day shortly after 11:00 a.m.

The Herrings began their evening cacophony of yelps, mews and caws around 4:45 p.m., and at 5:10 p.m., approximately 3/4 of them took wing in unison and flew out quite a distance over the lake. Why some Herrings stayed in the harbor is puzzling, but the majority of Ring-billeds (~ 150) stayed in the harbor as well. With that said, I'd point out that birds noted coming into the harbor during the early morning hours were ones that very likely roosted on Lake Michigan.

An intermediate Thayer'/Kumlien's type, tending towards Kumlien's. NPM, IL. 26 FEB 2012.
A well-marked adult Thayer's.
As for other notable sightings, we did tally all 7 expected gull species. It's difficult to be certain which were counted more than once, so these numbers are ONLY minima at best, accounting for the possibility of recounts:

11 Thayer's Gulls (8 distinct adults, 1 second cycle, 2 first cycle).
4 Kumliens' Iceland Gulls (4 adults. One of these adults showed all white wingtips but with upperparts that matched Herring - see photos).
2 Glaucous Gulls (1 adult, 1 first cycle).
7 Lesser Black-backed Gulls (4 adults, 1 third cycle, 2 first cycles).
1 Great Black-backed Gull (1st/2nd cycle).

Adult Kumlien's Gull with stage zero wingtip pattern. Upperparts matched surrounding Herrings.
Other: 2 adult Thayer's/Kumlien's -type intergrades were observed and are probably best left as "in between" birds. It's always difficult making a quick assessment of these birds in flight, but detailed photographs have made this easier.

Left as an intermediate type although likely a Kumlien's (note the slaty black-ish color on the wintips). The combination of an all white tip to P10, unmarked P5, broken subterminal band on P6, white tongue merging into mirror on P9 and faint dark gray band on underside of primaries are all suggestive of Kumlien's.

Tending towards Kumlien's (same bird as above).
Adult Thayer's.
I find it interesting that LBBGs outnumbered Kumlien's (I think this was the case last year as well), but admittedly, their darker upperparts make them hard to miss. I thought the chances of seeing a GBBG would be slim and I'm still puzzled by why this species is found in decent numbers a short distance to the north in WI, and in great numbers just a ways south in places like Calumet Park, Hammond and Whiting Indiana. Of our "special" winter gulls, Thayer's continues to dominate here and I suspect (gulp) there were at least 2 dozen of them present throughout the day. Overall, I was pleased with the numbers we reported.

Thayer's/Kumlien's in back with dark eye. American Herring in front.
First cycle Ring-billed Gull.

First cycle Thayer's (a bit on the pale end).
A special thanks to Al Stokie for his insightful thoughts on the gull dynamics in this part of Lake County - he and his team had the "harshest" part of the day. I'd also like to thank the Gyllenhaal's, Paul Sweet and Bob Erickson for manning part of the day. A similar two-day, consecutive, "Sit" will be conducted next winter in hopes of comparing Saturday/Sunday numbers. More volunteers will likely be needed -- some for NPM, some for Sand Pond, and some outside the Zion landfill. Please email me if you're interested in helping out.