Friday, September 8, 2017

Heermann's Gulls

Gulls are a fascinating group of birds, a group that seems to draw polarizing opinions from even the most inexperienced naturalist or quasi-outdoorsman.  To some, the "seagull" is a loud and brazen theft of picnickers' food, boisterous scavenger and fouler of pristine boat decks.  But to others, the group of birds known as the gulls is an intriguing bunch of intelligent, opportunistic, charismatic and slightly rougish birds; without their presence, our sea sides would be very dull indeed.

Heermann's Gull in Monterey, California, expressing his opinion and dispelling rumors!

There is no such thing as a "seagull."  Let us dispense with that falsity immediately!  (Likewise, "starfish" also do no exist; the correct generic term is sea star.)  The group that belongs to the family Lairdae, along with terns and skimmers, may be referred to generally as gulls, or specifically by each species' common name, such as Western Gull, California Gull, etc.  Nearly 20 species of gulls have been recorded in California, though not all are common, many are difficult to distinguish as juveniles or non-breeding adults, and still others may be hybrids.  More commonly, the average birder on the Central Coast of California can reasonably expect to see closer to eight or ten species during the year, though accurate identification can still be challenging!

Heermann's Gulls in various plumages: the birds in front and back are both adults transitioning from
breeding plumage (gray body and white head) to non-breeding plumage (mottled gray head). 
The dark-colored middle bird is a juvenile.

Heermann's Gulls (Larus heermanni) are one of our more attractive and distinctive gull species, the only gull in North America sporting a gray body and white head during the breeding season.  They can be found year-round throughout California's central coast region (specifically Monterey and Santa Cruz counties), their numbers highest between July and January. 

In December or January, Heermann's Gulls fly south to their breeding grounds off the coast of Mexico.  By March, most have arrived in Mexico to breed and raise their young.  After the young have fledged by midsummer, Heermann's Gulls return north along the Pacific Coast, some flying as far as southern British Columbia.  No other North American gull species breeds south of the United States.

Heermann's Gulls nest in colonies on arid islands off the coast of Mexico.  Nests are placed on the ground, often among boulders or grass, and consist of a shallow scrape in the ground with a minimal amount of lining.  According to Cornell's All About Birds, a few nesting attempts have been made in California by Heermann's Gulls, though all have failed.  It is expected that eventually they may succeed, driven north by increasing populations in Mexico.
Like other species of gulls, Heermann's Gulls are known for stealing food from other birds.  It has been observed that Heermann's Gulls have developed a particular, almost parasitic symbiotic relationship with Brown Pelicans (Pelecanus occidentalis).  The gulls specifically target these expert fishers, going so far as to steal fish directly from the pelican's pouch!  The relationship is so finely tuned that the northward migration of the Heermann's Gull coincides with that of the Brown Pelican. 

As expected, this flock of Heermann's Gulls was found near a flock of Brown Pelicans at Carmel River State Beach.

It is estimated that 90-95% of the world's breeding population of Heermann's Gulls nest on one island in the Gulf of California, Isla Raza.  The island has been protected as a wildlife sanctuary since 1964, but the birds are still vulnerable to human disturbance. 

As always, minimize disturbance when visiting natural areas and keep wildlife wild!  As much as they may insist, gulls don't need your tasty handouts of fries and chips!

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