11 December 2017

Another Slaty-backed Gull

A day trip to Kenosha County, Wisconsin yesterday was rewarded with this adult Slaty-backed Gull.

Adult Slaty-backed Gull (L. schistisagus). Pleasant Prairie, Wisconsin. 10 December 2017.

I found it at Lake Andrea around 1:00 pm after having spent the last 4.5 hours there, working a growing flock of Herring Gulls. The flock wasn't too shabby to begin with, giving up 11 Iceland

10 December 2017

Variable Widths to Inner Primary Tips in Iceland Gulls

A few years ago I began to notice a small percentage of adult-type Iceland Gulls (thayeri & kumlieni) that have relatively broad white tips to the inner primaries.

The most extreme of these types recalls a pattern not unlike the trailing edge on Slaty-backed Gull:
An unusual pattern with white tips to the inner primaries congruent in width to those of the secondaries. Also note how white eats into the feather shafts on p2-p5. Chicago. January.

I've only seen 3-4 birds similar to the one above. Others generally have slightly more narrow tips to p1-p2, but widen thereafter.

09 December 2017

Detecting Thayeri P9 Patterns

Outer primary patterns in large gulls provide much appeal to the discerning eye. One particular pattern that "pops" is the so-called thayeri pattern found on the 9th primary:

The mirror on p9 merges with a white inner web. © Martin T. Elliott

This pattern is found on multiple taxa - not only Thayer's - but is only visible when the primaries are sufficiently spread. Below is a short series of the same bird demonstrating this:

The inner web to p9 is sufficiently exposed with the primaries spread.

As the wing begins to fold the inner webs are less exposed.

No thayeri pattern is detected here as the inner web to p9 is covered by the outer web of p8. 

With many contemporary papers on large gull ID relying less on "birds in the hand" and museum specimens, it's imperative that fully spread wings are obtained. Digital photography has made capturing these details relatively simple, and it allows a closer look at what would otherwise be fleeting glimpses in the field.

01 December 2017

Monthly Notables November 2017

  • Sabine's Gull (1st cycle). Gila County, Arizona. 03 November 2017.
  • Lesser Black-backed Gull (adult). Los Angeles, County, California. 03 November 2017.
  • Sabine's Gull (1st cycle). Lake County, Tennessee. 03 November 2017.
  • Slaty-backed Gull (3rd cycle). Labrador-Happy Valley-Goose Bay County, Newfoundland & Labrador. 04 November 2017.
    • 2nd record for Labrador. Incidentally, the 1st record was only last year in April 2016. That individual was an adult, found roughly 1 mile away from the 2017 bird.
  • Great Black-backed Gull (2nd cycle type). Stark County, North Dakota. 05 November 2017.
  • Little Gull (adult). Lawrence County, Alabama. 12 November 2017.
  • Lesser Black-backed Gull (adult). Inyo County, California. 12 November 2017.
  • Black-headed Gull (adult). Butler County, Pennsylvania. 12 November 2017.
    • A returning adult since at least 2011. 8 county records which may prove to be of the same individual.
  • Thayer's Gull (1st cycle). Mohave County, Arizona. 17 November 2017.
    • Only about the 15th record for the state.
  • Black-legged Kittiwake (adult). Sedgwick County, Colorado. 16 November 2017.
  • Little Gull (1st cycle). Okanagan-Similkameen District, British Columbia 17 November 2017.
    • First record for the Okanagans.
  • California Gull (adult). Lake County, Illinois. 19 November 2017.
  • Black-legged Kittiwake (1st cycle). Scott County, Iowa. 20 November 2017.
  • Black-legged Kittiwake (1st cycle). Washington County, Minnesota. 24 November 2017.
  • Thayer's Gull (1st cycle). Accomack County, Virginia. 24 November 2017.
  • Black-legged Kittiwake (1st cycle). Battleford County, Saskatchewan. 25 November 2017.
  • Black-legged Kittiwake (2 - 1st cycle). Sangamon County, Illinois. 29 November 2017.
  • Great Black-backed Gull (1st cycle). Polk County, Iowa. 30 November 2017.
    • Rare for inland Iowa. 


A relatively large influx of Ross's Gulls was found in the Gambell, Alaska region beginning on 13 November, and continued through the end of the month. Some estimates put numbers at 14-20 birds roaming the waters of the northwest portion of St. Lawrence Island.

Black-legged Kittiwakes were reported in above-average numbers, inland, on the western Great Lakes and beyond.

An adult 'Taimyr Gull' was reported in Sonoma County, California (24 November 2017). It's believed this individual is a returning bird, first found last winter. The taxonomy of this form remains unsettled and has yet to be clarified.

30 November 2017

November 2017 Quiz

Age/Molt stage: This appears to be a large 3 or 4-year, large white-headed gull. Given the black markings on the tail, we can be sure it's not a definitive adult. It appears the outer primary is still growing in, as are some inner secondaries, and so the prebasic molt hasn't concluded.

Flight Feather Molt in November Lake Michigan Iceland Gulls

Wisconsin Point Thayer's Bonanza