28 October 2012

Primary Molt in an Adult Ring-billed

Adult Ring-billed Gulls typically complete their prebasic molts by the end of October. Here's a series of photos documenting primary growth of a known-age RBGU taken at Rainbow Beach in Chicago, Illinois. The photos are presented in three week intervals from late August through late October.This male was banded in the breeding season of 2007 at the Lake Calumet colony.

Just two white primary tips clearly showing past the tertials on 25 August 2012.
Three primary tips showing past the tertials on 15 September 2012. P8 grew significantly in the last three weeks.
Now 4 primary tips showing beyond the tertials on 06 October 2012.
Finally, the tip to P10 (black) has emerged from underneath P9. 26 October 2012. This generally concludes the prebasic molt as most of the body and flight feathers are renewed by the time P10 is fully grown.
The primaries, secondaries and rectrices are all new, crisp, feathers that will get this bird through the winter, spring and most of the next breeding season.

One thing worth noting here is that the mirrors on P10, and particularly P9, are relatively small. This may be an indication as to what an adult this young (6th cycle) should look like, but it's not uncommon for some adults to be without a mirror on P9 entirely. Are these young adult females? Also, might the choppy black markings up the inner web of P8 become "cleaner" as this bird ages? The black marks on the outermost greater primary coverts above P10 are not a sign of "subadultness" - this is an expected feature on adult Ring-billeds.

Rainbow Beach. Chicago, IL. 26 Oct 2012.
To read more about why this bird was tagged, click here.

27 October 2012

California Gull in New Buffalo Michigan

American Herring Gull numbers are beginning to build significantly at various hotspots along lower Lake Michigan. This only means one thing: among them will be some goodies!

I went out to Berrien County Michigan today to observe the relatively large number of Lesser Black-backeds, of which there were plenty, but much more surprising was this California Gull:
California Gull (1st cycle). New Buffalo, MI. 27 October 2012.
The mostly pink bill with black tip grabbed my attention right away. First cycle American Herrings don't typically loose that much black to the bill this early in the fall, and when they do, it appears as a blend of black and pink and is not as sharply demarcated as in CAGU. Also, the post-juvenile molt of the scapulars is rather advanced for the 1st cycle Herrings we're seeing on southern Lake Michigan right now. The gray coloration also stands out and is a bit dark for a Herring.

Overall, this bird appeared messier than the surrounding first cycle smithsonianus birds that were present, but I should mention that 1st cycle CAGUs on the West Coast currently appear much messier than this individual and don't have such "nice" looking post-juvenile scaps right now. Alvaro Jaramillo explained to me that this bird's upperwing coverts are exceptionally neat and appear very "Herring-like". The uniform gray on the scaps is also much "neater" than what is being seen on October CAGUs along the Pacific.

Note the "double" wing bar formed by the darker bases to the greater coverts. It's not uncommon for CAGUs to have a few inner primaries with pale inner webs which resembles Herring.

As for Lessers, I found at least 5 (3 first cycles, 2 adults) but probably could have pulled out another sub-adult if I had the time to comb through the incoming flocks. These birds use the beach as a preen/lube spot before roosting out on the lake for the night.
First cycle LBBG

First cyle Lesser harassaing adult Ring-billed.
Two of the three young Lessers working the surf together.
My estimate of the number of American Herrings at this site is between 600-700 birds. It's not even November yet! WOW!!


 And one last shot of the Cali Gull's wings:

10 October 2012

Another Cinnamon Ring-billed

Here's another juvenile Ring-billed Gull showing cinnamon tones throughout:

Rainbow Beach. Chicago, IL. 06 October 2012.
It shows limited post-juvenile molt of the scapulars (PA1) and has retained a good amount of juvenile chest, neck and head feathers.

Compare this to the first basic individual below:

Tinley Park, IL. 27 September 2012.
It's hard to believe these are both hatch-year birds given the amount of post-juvenile molt this second individual exhibits. Most of the scapulars have been replaced along with many median and some lesser upperwing coverts. Most urprising though is the renewal of the tertials via PA1 - this is an exception in first cycle birds. A possible explanation for the difference in these two birds is "early hatch" versus "late hatch" coupled with the former being somewhat delayed and the latter advanced.

03 October 2012

Berrien County Gulls

One thing I've tried to do more of lately is get out to Berrien County, Michigan as fall migration picks up. Some photos from this past Sunday:

First cycle Franklin's. First found resting about 200 yards out on the lake with a few of the large gulls, this bird readily came in when the Ring-billeds started feeding on my offerings.
Adult Bonaparte's Gull. This bird, along with another first cycle below, came right in and landed on the beach.
First cycle Bonaparte's.
 The only large gulls of note were two Lesser Black-backeds - one adult on the lake at Warren Dunes SP, and one 2nd cycle at the beach  at New Buffalo. The adult was way too far out resting on the lake and the 2nd cycle was a flyby:

2nd cycle Lesser Black-backed.