0 the heermann's gull (larus heermanni) is a gull resident in the united states , mexico and extreme southwestern british columbia , nearly all nesting on isla rasa in the gulf of california .
1  they are usually found near shores or well out to sea , very rarely inland .
2  the species is named after adolphus lewis heermann , nineteenth-century explorer and naturalist .
3 this species looks distinctly different from other gulls .
4  adults have a medium gray body , blackish-gray wings and tail with white edges , and a red bill with a black tip .
5  the head is dusky gray in non-breeding plumage and white in breeding plumage .
6  immatures resemble non-breeding adults but are darker and browner , and the bill is flesh-colored or pink till the second winter .
7  a few birds , no more than 1 in 200, have white primary coverts , which form a showy spot on the upper wing .
8  this gull is unlikely to be confused with other species as it is the only white-headed , gray-bodied gull found on the west coast of north america .
9 calls are described as deep and similar in pattern to other gulls but noticeably different in quality .
10 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 .
11  after breeding , birds commonly disperse to central california , and less commonly north as far as british columbia and south as far as guatemala .
12 this species nests colonially on the ground , like many gulls .
13  the nests are often at densities as high as 110 nests per 100 m2 (1,100 sq ft) .
14  it lays two or three eggs , grayish buff , to buff with gray and brown markings .
15 heermann's gull sometimes steals prey from other seabirds , particularly brown pelicans , with which it often associates .
