28 June 2016

Sheboygan Gulls - Late June

For a small Midwestern town that sits on the western shore of Lake Michigan, Sheboygan, Wisconsin can hold relatively nice numbers of larids in the summer months (primarily May-July). I recorded 7 species there on Friday, missing an 8th species (Franklin's Gull) seen by others.

  1. Little Gull (5-6)
  2. Bonparte's Gull (700+)
  3. Laughing Gull (2)
  4. Ring-billed Gull (200+). Breeder.
  5. Herring Gull (125+). Breeder.
  6. Lesser Black-backed Gull (23+)
  7. Great Black-backed Gull (2)

So what would attract these birds to Lake Michigan in late June? Sheboygan sits well south of the breeding grounds of species like Bonaparte's, Little Gull, and presumably Lesser Black-backed Gull. And aren't Great Black-backs and Laughing Gulls coastal species?

Eat & Molt - Simple

The majority of the unexpected gulls here are sub-adults that are in the midst of a complete molt (prebasic molt) and have no pressing reason to situate themselves among a colony of conspecifics. So long as a reliable food source is available - and a reliable food source there is - the gulls summer here under low-pressure conditions, and complete their molts.

LBBG. Sheboygan, WI. 24 June 2016.

This bird has begun its 2nd prebasic molt. Three inner primaries have been renewed, with the fourth primary about half grown.The greater upperwing coverts have been dropped exposing the white bases to the secondaries. A mostly complete set of new median wing coverts is visible too.

On a "good" year like this, the food source is no other than alewives. The young fish are stagnant near shore where they're either close to dying or already have perished. The gulls don't bother with the dead fish. Instead, they go for the "fresh" ones that are almost dead. This makes for easy pickins'.

A 1st summer Bonaparte's with a nice-sized alewife. In front sits a similar-age Little Gull.

Any bird coming this close to shore, allowing this sort of approach, must have something good it wants to eat.

This Lesser Black-backed Gull made the whole process look easy...

Greater Lessers than All the Land of Great Lakes

Speaking of Lesser Black-backeds, I know of no other site on the Great Lakes where one can easily find 20+ individuals loafing around on one beach in the breeding season. In one scan I counted 23 birds (all 1st and 2nd summer), but I'm sure I saw over 30 on this day (photographs show unique 3rd summer types that weren't counted with the 23 scan).

Yes, Lessers! How many? My count is 15.
Young Lesser Black-backs can be a bit tricky to nail, especially since many of the 1st summer Herrings can show solid, dark upperparts on their 2nd generation feathers.

How many Lessers in this image? I can't confidently make out a single one.
Many 1st/2nd summer Lessers retain more black on the bill, like this one of the left (although NOT always). Also note the longer wing projection and attenuated look to the rear. The other two are Herrings (notice the right bird has lighter gray scapulars that have recently grown in).
From left to right: Herring, Herring, Lesser, Lesser, Herring, Herring, Lesser. The stuctural clues on the LBBGs is primaries that project farther pass the tail, smaller heads and straighter bills (but not necessarily shorter).

Little Gull numbers here aren't too shabby either. Sheboygan and Manitowoc, Wisconsin are among the top 5 sites on the Great Lakes to see this species in summer.

Two Little Gulls with similar-aged Bonaparte's in the background.

Little Gull with new greater coverts grown in. Two Bonaparte's in the back.
Soon the alewives will be virtually non-existent on the lakefront...by late July/early August most of these birds will have moved on.