Heermann's gull (Larus heermanni) is named after Adolphus Lewis Heermann, a 19th century American doctor, naturalist, ornithologist, and explorer. He collected specimens of birds, animals, and plants in the western United States and some were named after him including another bird, Heermann’s song sparrow. Breeding adults are dark grey above, grey below, with a white head, black legs, and a red bill with black tip. Non-breeding adults are similar but with streaky heads. Immatures are very dark sooty brown overall, with a pale bill that shows a dusky tip.