Heermann's Gull

The Heermann's Gull (Larus heermanni) presents a striking figure with its medium gray body, contrasting blackish-gray wings and tail adorned with white edges. In breeding plumage, the head is a resplendent white, while in non-breeding plumage, it adopts a dusky gray hue. The red bill, tipped with black, is a distinctive feature of the adult. Immature birds share a resemblance with non-breeding adults but are discernibly darker and browner. Their bills, a youthful pink, mature by the second winter. A rare few, perhaps one in two hundred, boast white primary coverts, creating a conspicuous spot on the upper wing. This gull is a unique sight along the west coast of North America, unlikely to be mistaken for any other species due to its singular white-headed, gray-bodied appearance.

Identification Tips

When observing Heermann's Gulls, look for the red bill with a black tip, a key identifier. Adults in breeding plumage will have white heads, while those in non-breeding plumage and immatures will display a dusky gray. The white-edged blackish-gray wings and tail are also telltale signs of this species.

Habitat

Heermann's Gulls are coastal dwellers, typically found near shores or out at sea, and very rarely venture inland.

Distribution

The majority of Heermann's Gulls, about 90% of the population, breed on Isla Rasa in the Gulf of California. They can be found from Mexico to extreme southwestern British Columbia, dispersing post-breeding to areas as far north as central California and occasionally reaching British Columbia and south to Guatemala.

Behaviour

This gull species is colonial in its nesting habits, laying two to three eggs that are grayish buff to buff with gray and brown markings. The nests are densely packed, sometimes reaching 110 nests per 100 square meters. Heermann's Gulls have been known to engage in kleptoparasitism, pilfering prey from other seabirds, notably the brown pelican.

Song & Calls

The calls of the Heermann's Gull are deep and resonate with a pattern similar to other gulls, yet with a distinct quality that sets them apart.

Breeding

Heermann's Gulls nest colonially on the ground, with a high nest density. They lay two to three eggs that are grayish buff to buff, adorned with gray and brown markings.

Similar Species

Due to its unique coloration and red bill with a black tip, the Heermann's Gull is not easily confused with other species along the west coast of North America.

Diet and Feeding

The diet of Heermann's Gull includes small fish, marine invertebrates, lizards, insects, refuse, and carrion.

Conservation status

The IUCN has classified the Heermann's Gull as "Near Threatened." The species faces vulnerability due to its breeding concentration on a single small island, Isla Rasa, which is a sanctuary since 1964. The breeding success is highly dependent on prey availability, which fluctuates with ocean temperature changes, particularly during El Niño events.