Heermann's Gull
Encyclopedia
The Heermann's Gull is a gull
resident in the United States
, Mexico
and extreme southwestern British Columbia
. Of the current population of about 150,000 pairs, 90% nest on the island of Isla Rasa off Baja California
in the Gulf of California
, with smaller colonies as far north as California
and as far south as Nayarit
. After breeding, birds commonly disperse to central California, and less commonly north as far as British Columbia
and south as far as Guatemala
. They are usually found near shores or well out to sea, very rarely inland.
This species looks distinctly different from other gulls. Adults have a medium gray body, blackish-gray wings and tail with white edges, and a red bill with a black tip. The head is dusky gray in non-breeding plumage and white in breeding plumage. Immatures resemble non-breeding adults but are darker and browner, and the bill is flesh-colored or pink till the second winter. A few birds, no more than 1 in 200, have white primary coverts, which form a showy spot on the upper wing.
Calls are described as deep and similar in pattern to other gulls but noticeably different in quality.
This species nests colonially on the ground, like many gulls. It lays two or three eggs, grayish buff, to buff with gray and brown markings.
Heermann's Gull sometimes pirates
prey from other seabirds, particularly Brown Pelican
s, with which it often associates.
Isla Rasa was declared a sanctuary in 1964, and egg-collecting and disturbance during the breeding season are discouraged. Current threats to this gull include the effects of weather on prey species.
Gull
Gulls are birds in the family Laridae. They are most closely related to the terns and only distantly related to auks, skimmers, and more distantly to the waders...
resident in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
and extreme southwestern British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
. Of the current population of about 150,000 pairs, 90% nest on the island of Isla Rasa off Baja California
Baja California
Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...
in the Gulf of California
Gulf of California
The Gulf of California is a body of water that separates the Baja California Peninsula from the Mexican mainland...
, with smaller colonies as far north as California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
and as far south as Nayarit
Nayarit
Nayarit officially Estado Libre y Soberano de Nayarit is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 20 municipalities and its capital city is Tepic.It is located in Western Mexico...
. After breeding, birds commonly disperse to central California, and less commonly north as far as British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
and south as far as Guatemala
Guatemala
Guatemala is a country in Central America bordered by Mexico to the north and west, the Pacific Ocean to the southwest, Belize to the northeast, the Caribbean to the east, and Honduras and El Salvador to the southeast...
. They are usually found near shores or well out to sea, very rarely inland.
This species looks distinctly different from other gulls. Adults have a medium gray body, blackish-gray wings and tail with white edges, and a red bill with a black tip. The head is dusky gray in non-breeding plumage and white in breeding plumage. Immatures resemble non-breeding adults but are darker and browner, and the bill is flesh-colored or pink till the second winter. A few birds, no more than 1 in 200, have white primary coverts, which form a showy spot on the upper wing.
Calls are described as deep and similar in pattern to other gulls but noticeably different in quality.
This species nests colonially on the ground, like many gulls. It lays two or three eggs, grayish buff, to buff with gray and brown markings.
Heermann's Gull sometimes pirates
Kleptoparasitism
Kleptoparasitism or cleptoparasitism is a form of feeding in which one animal takes prey or other food from another that has caught, collected, or otherwise prepared the food, including stored food...
prey from other seabirds, particularly Brown Pelican
Brown Pelican
The Brown Pelican is the smallest of the eight species of pelican, although it is a large bird in nearly every other regard. It is in length, weighs from and has a wingspan from .-Range and habits:...
s, with which it often associates.
Isla Rasa was declared a sanctuary in 1964, and egg-collecting and disturbance during the breeding season are discouraged. Current threats to this gull include the effects of weather on prey species.