Black-headed Gulls On The Reservoir

Birders patient enough to look through all of Central Park’s gulls have been rewarded with some rarities this winter. In January, we had a Short-billed Gull, Glaucous Gull, and a few Lesser Black-backed Gulls, Iceland Gulls and Black-headed Gulls. These gulls were in addition to our regular Ring-billed Gull, American Herring Gull and Greater Black-backed Gull species which we see daily during the winter.

Over the last few weeks, we’ve been seeing the return of some Black-headed Gulls. What’s unclear is how many different individuals we’re seeing. We’re seeing at least one in adult plumage and at least two different individuals in 1st cycle plumage, possibly three.

These are rare gulls, so on eBird to report them one is asked to include a picture and/or a description. What has been interesting to see this week is that some comments included the word “continuing”. I even used the word in a Discord post. While this made sense for the single Snow Goose and the pair of Common Mergansers that were seen on the reservoir consistently this winter, for this last week it doesn’t for the Black-headed Gulls. We’ve seen at least four different individuals this March.

Adults
The gull seen on March 16th and 20th could easily be the same gull transitioning to alternate plumage.

Adult – January 27

Adult, March 16

Adult – March 20

Sub-Adults
There are at least three different individuals being seen in March, maybe more. The gull seen on March 15 has a darker head than the ones seen later in March. Also the bird on March 18 has a tail that ends in a black band, while the others had a black subterminal band, with a thin bad of white at the tip of the tail.

What has been an interesting lesson for me is how different the head marking appears based on the posture of the bird and the light. The dark earspot can appear round when the head is raised and appear as a crescent when the bird is resting. Also, as the plumage changed, the darker feathers just coming in on the hood can be hidden or be seen depending on the angle or the light. Even the leg and the bill color changes depending on the light.

Sub-Adults – January 18