Measurements
Both Sexes
- Length
- 18.1–20.9 in
46–53 cm - Wingspan
- 40.9–45.3 in
104–115 cm - Weight
- 13.1–22.7 oz
371–643 g
Other Names
- Goéland de Heermann (French)
- Gaviota de Heermann, Gaviota mexicana (Spanish)
Cool Facts
- The Heermann's Gull, like many other gulls, frequently steals food from other birds. The Brown Pelican is a frequent victim. An adult Heermann's Gull is most likely to try to steal food from an adult pelican, and an immature gull is more likely to steal from an immature pelican.
- The Heermann's Gull is the only North American gull that breeds south of the United States and comes north to spend the nonbreeding season. After breeding is over in July, the gull quickly comes north all the way to southern Canada. It heads back southward by December, and most breeders are at the breeding islands by March.
- Perhaps as a result of the increasing populations in Mexico, several attempts have been made by Heermann's Gulls to breed in California. The first was on the island of Alcatraz. So far these attempts have been unsuccessful, but eventual successful nesting is expected.
Habitat
Shore-line
- Nests on arid offshore islands.
- Winters along coast and out to sea.
- Rarely inland.
Food
Fish
Small fish, marine invertebrates, lizards, insects, refuse, and carrion.
Nesting
Nesting Facts
- Clutch Size
- 1–3 eggs
- Egg Description
- Pale bluish gray to olive, with brown blotches.
- Condition at Hatching
- Semiprecocial with eyes open. Covered in down, grayish white mottled with dusky on back, pinkish buff on head and underparts.
Nest Description
Nest a shallow depression in the ground, or an open platform of sticks, dry grass, and weeds. Nests in colonies among boulders or nestled in grass.
Nest Placement
Ground
Behavior
Aerial Dive
Picks food from surface of water, plunges into water to pursue fish. Hovers and dips over waves. Steals food from marine mammals and other birds.
Conservation
Near Threatened
Vulnerable to human disturbance because 90-95% of the total world population breeds on one island, Isla Raza. The island was made a wildlife sanctuary in 1964, and populations have increased since then.
Credits
- Islam, K. 2002. Heerman's Gull (Larus heermanni). In The Birds of North America, No. 643 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.