A Very Common Species Provides a Very Big Surprise

Cooper Island, Alaska, July 27, 2010 — When my interest in bird-watching first developed in the 1960s (the avocation would not be called “birding” for a number of years), a common wintertime activity was visiting the Cleveland lakefront and scanning the flocks of gulls for any interesting vagrants among the large number of Herring Gulls that wintered on the south shore of Lake Erie. One of our “fantasy birds” was the Glaucous Gull. The thought that this large and very pale arctic species might visit our temperate latitudes was very exciting and a sighting would provide a link to remote northern areas which, at that point in my life, were also the stuff of fantasies.

My arrival in Barrow in the early 1970s modified my view of Glaucous Gulls rather rapidly when, on my first trip past the Barrow landfill, I saw hundreds of Glaucous Gulls feeding on the village’s garbage. Over the past forty years I have seen Glaucous Gulls in every possible tundra and marine habitat and also preying or scavenging on almost every possible food source. I still consider them a beautiful gull but their ubiquity means that any individual Glaucous Gull flying past the island does not warrant a second glance. I pay some attention to the odd individual attracted to the guillemot colony in hopes of preying on eggs or chick, but soon realizing that the nest boxes prevent predation on nest contents. Last summer they impressed me with their numbers as thousands gathered to feed on the krill wash-ups that were attracting thousands, and possibly tens of thousands, of Arctic Terns and Sabine’s Gulls.

Ice-remnants Cooper Island

Ice remnants along the coast of Cooper Island

Given my history with Glaucous Gulls I did not think they could easily surprise or engage me but that all changed this summer in early July when I took a walk to the east end of the island with my visitors from the BBC. Next to a grounded fuel barge that marks the end of the island I saw a conical mound of peat that was not present last year and which, upon closer examination, was found to harbor a Glaucous Gull nest — the first on Cooper Island in at least 35 years and probably much longer than that. I was truly taken aback, although given the abundance of the species in the region, the discovery did not have the same impact on me as lifting up a box in 1972 and finding the first Black Guillemot nest in the Beaufort Sea. The Plover Islands, of which Cooper Island is the largest, are not typical Glaucous Gull nesting habitat. While Glaucous Gulls breed in a wide range of habitats on the mainland their colonies on barrier islands are typically limited to locations near river mouths that have open water earlier in the season than places like Cooper.

george-gull-nest

George inspect a Glaucous Gull nest.

My discovery of the nest at the east end of the island did not prepare me for what I discovered a week later when I censused the west end of the island. After finding a small number of tern and Sabine’s Gull nests I was about to head back to the cabin when I noticed two Glaucous Gulls acting territorial. As I left the area one of the gulls set down on what looked to be a driftwood pile but proved to be the second Glaucous Gull nest I have ever found on the island. The discovery of the second nest was almost more of a surprise than the first in that there was no clear connection between the two nests. The four-mile distance between them precludes there being any social facilitation and it appears that two pairs of gulls independently made the decision to breed on the island. When I went back to visit the west-end nest a few days later I was delighted to find a chick and the other egg in the process of hatching.

A Glaucous Gull nest

A Glaucous Gull nest

The reasons for and implications of this most recent addition to the small list of birds breeding on Cooper Island are not clear. At the simplest level it may be that last summer’s abundance of nearshore prey enticed some previously nonbreeding gulls (out of the thousands feeding here) to consider Cooper as a suitable breeding location. This year the krill wash-ups have yet to occur but even in their absence it is likely that the nearshore waters near Cooper Island can provide enough scavenging and predation opportunities to raise a few gull chicks. While it seems unlikely that Cooper Island could support a large gull colony sometime in the future, I thought the same thing about Brant twenty years ago when the first pair bred on the island. There are now 75-100 pairs of Brant within sight of my cabin.

cooper-island-glaucous-gull-chick

Newly hatched Glaucous Gull chick and an egg in the process of hatching

Glaucous Gull chicks leave the nest rather soon after hatching so tracking fledging success of the two nests could be difficult. More importantly the time I can spend monitoring the gulls is now limited as Black Guillemot hatching is in full swing with approximately 80 chicks appearing in the past few days with enough eggs to triple that chick count in the next week. The new chicks are benefitting from the ice that remains adjacent to the island with its associated Arctic Cod. The big question now is how long that ice will persist and how the month of August — with its potential for bear predation, puffin disturbance and prey shortages — treats this year’s crop of nestlings.

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