31 July 2014

Juvenile Ring-billeds: Late July

A small selection of juvenile Ring-billeds, photographed on the very southern tip of Lake Michigan, in East Chicago, Indiana:

Brown type. East Chicago, IN. 26 July 2014.

Intermediate type. East Chicgao, IN. 26 July 2014.
Besides the subtle variation in the bill patterns, also note the immense differences in leg color, so early on in the season.

Ghost type. East Chicago, IN. 26 July 2014.
Peter Pyle recently informed me that it's not very unusual for juvenile feathers to show color patterns that are found in formative feathers. This adds to the excitement of trying to determine whether some of these feathers are juvenile or not, especially with species like RBGU that begin molting in earnest after leaving their natal colonies. Consider this individual:

Ghost type with a considerable amount of gray juvenile feathers. East Chicago, IN. 26 July 2014.
Here's this same individual with outer primary still growing out:

Note the extensive gray in the juvenile greater coverts and in the scapulars sitting over the proximal side of the wing.
I suspect that 2nd generation feathers (whether replacing feathers that were dropped accidentally or via molt) look longer, broader and tend to be "fluffier", covering a number of smaller adjacent juvenile feathers, like this:

Note the long broad, gray, median covert that has a different pattern than the surrounding "true" juvenile feathers.

The progression of 2nd generation feathers is obvious once it begins. Here are several birds that illustrate this nicely, spanning from August through September of their hatch year - all photographed on Lake Michigan:

24 July 2014

Accidental Versus Deliberate Feather Replacement

As more juveniles of all our species begin to appear in the next weeks, it's important to bear in mind that some feathers are replaced "accidentally" while others "deliberately" by traditional molts.

In the first stages of juvenile feather growth, some 1st basic feathers may grow out weak, defective, or even be tugged at by adults. These feathers are dropped, adventitiously. Take for instance this hatch year Ring-billed with a renewed mid-primary:

Ring-billed Gull (1st cycle) with adult-like primary flight feather. Chicago, IL. 05 Nov 2011.
First cycle Ring-billeds don't begin molting their primaries until May of their second calendar year via the 2nd prebasic molt. This adult-like feather has replaced a juvenile primary that was dropped "accidentally". As a rule, most of our gulls in the northern hemisphere retain their flight feathers, including rectrices, until early spring of their 2nd calendar year. Franklin's and Sabine's Gulls, which are our only "true" transequatorial migrants, are exceptions.

This is not to say that hatch-year gulls shouldn't show new, adult-like, gray feathers. Many deliberately replace their feathers via a strategic molt soon after leaving their nest site. For example, here's a recently fledged juvenile Ring-billed showing a couple of gray upperwing coverts:

Ring-billed (juvenile). Tinley Park, IL. 23 July 2014.
Hatch-year Ring-billeds begin their prealternate molts (or possibly preformative molts?) as early as late July, usually beginning with their scapulars and some with upperwing coverts. This relatively quick replacement of juvenile feathers is said to occur for two reasons: 1) Ample food supply, and, 2) The demand for a more rugged and stronger set of feathers that will be needed in the upcoming winter.

Some of our gulls replace most or all of their scapulars via a prealternate (or preformative) molt in their hatch year, like these individuals:

California Gull (1st cycle) with replaced, gray, scapulars. New Buffalo, MI. Oct 2012.
Ring-billed (1st cycle) with replaced scapulars, some upperwing coverts AND a few upper tertials. Chicago, IL. Oct 2012.
Bonaparte's Gull (1st cycle) with replaced scapulars. Chicago, IL. Oct 2010.
Note that the gray greater and median coverts on the Bonaparte's above are not preformative feathers. These are juvenile feathers that were originally grown as gray. This is a variable trait found in a number of species. One example that comes to mind are the silvery gray-tinged greater coverts of some Ring-billeds.

Ring-billed Gull (1st cycle) with extensive gray on juvenile greater coverts. Chicago, IL. 04 July 2013.
An extreme example of juveniles that begin with a sizable percentage of their upperparts showing adult-like gray, are kittiwakes. Take this Black-legged Kittiwake, for instance:

Black-legged Kittiwake (1st cycle) with gray juvenile upperwing coverts and scapulars. Marseilles, IL. Dec 2013.
Most gulls that show gray on their backs acquire that color through a second generation of feathers by molt, making 1st winter kittiwakes an interesting case.

Knowing which feathers are supposed to be replaced "when" is lots of fun to monitor and observe throughout the year. Fortunately, gulls and their feather tracts are large enough, and usually cooperative enough, for us to study in the field with some ease.

17 July 2014

Lesser Black-backeds Galore: Sheboygan, Wisconsin

On Friday, 11 July 2014, I recorded a "Lake Michigan" personal high count of 20 Lesser Black-backed Gulls on the Sheboygan lakefront - a count I've imagined would only be possible in winter. After spending more than 5 hours between Deland and North Point parks, I was confident that at least twenty individuals were present (16 seen together off the point near the gazebo). The age breakdown was 13 first summers, 5 second summers and 2 third summers - no adults!

Between Deland and North Point. Six Lesser Black-backeds shown in this small group, outnumbering the Herrings
A collection of some of the more photogenic individuals:

The so-called mystery gull from my last post (left) is now showing fairly typical Lesser Black-backed inner primaries. Structurally, it looks perfectly fine for that species, almost exactly matching the darker LBBG on the right.

Also of interest was a very cooperative 1st cycle Great Black-backed, catching approximately 1 fish every 4 minutes (this went on for roughly 25 minutes). Keep in mind that Great Black-backed is one of our most skittish gull species on the Great Lakes.

Great Black-backed (right) seen here with a Lesser Black-backed (left).
I worry about the easy pickings at this site. The dying alewives and shad may be an undetected problem for these birds. Most of the gulls don't eat the dead fish that litter the shoreline, but they readily catch the slowly-dying individuals. One has to wonder if the fish here are carrying Type E botulism. Historically, this bacteria has been responsible for the death of thousands of gulls, terns, cormorants and other water birds on the Great Lakes, and Lake Michigan is no exception. For a great account of this unfortunate phenomenon, I'd recommend reading, "The Dismal State of the Great Lakes", by James Ludwig.

Another highlight of the day was a 1st summer Thayer's Gull (different than the bird Ethan Gyllenhall, Alex Hale and I observed on 08 June):

Well into its 2nd prebasic molt (p1-p5 fully grown, p6 3/4 grown, p7 1/2 grown, p8 dropped, p9-p10 retained 1st basic.
Finally, some open wing shots of the Lesser Black-backeds, displaying an array of primary molt patterns, with the least having only renewed to p3, and some all the way out to p8:

Somewhat puzzling was these two fledgling Herrings, not yet suited for flight, sitting on the lakefront with partial down. I only noticed them coming out of the vegetation when I was already too close for comfort.

They quickly made their way to the water and swam away as one of the presumed parents began circling over my head and threatening an attack. I hit the road after a, good, long afternoon of summer gulling with the juveniles to my back, wondering what the chances of survival will be for these Lake Michigan Herrings.