Aleutian Tern vs Sooty Tern

Aleutian Tern

Onychoprion aleuticus

Medium120 gCoastal

The Aleutian tern is medium-sized tern (32–39 cm (13–15 in) long), with a 75–80 cm (30–31 in) wingspan, a short pointed bill and a long, deeply forked tail. It weighs 84–140 g (2.9–5.0 oz). Breeding adult and juvenile are the only plumages likely to be encountered in North America. Breeding adult (definitive alternate plumage) has a white forehead, a black cap, a mid-grey mantle with darkish grey underparts, and white rump and tail. Its underwing is whitish, with dark-tipped primaries and a diagnostic dark bar on the secondaries. The Aleutian tern has a black bill as well as black legs. Voice: The Aleutian tern is associated with different calls reported in the literature. Their call can be distinguished from the common tern ones, since it has a higher pitch and is characterized by a soft and rolling whistled tone. The most distinctive sound is the choppy "chif-chif-chu-ak" described by Olsen and Larsson in 1995, less harsh than the sustained note of the Arctic tern.

ID text from Wikipedia, CC BY-SA 4.0

Photo: usgs.gov · Public domain

Sooty Tern

Onychoprion fuscatus

Medium186 gMarine

It is a medium-large tern, similar in size to the Sandwich tern (Thalasseus sandvicensis) at 36–45 cm (14–17.5 in) long with an 82–94 cm (32.5–37 in) wingspan. The wings and tail are long, and it has black to dark blackish-brown upperparts and white underparts, and a white forehead. The tail is moderately deeply forked (more deeply forked than in Thalasseus terns, but less deeply than most Sterna terns), black, with white outer edges. It has black legs and bill. The average life span is 32 years.

ID text from Wikipedia, CC BY-SA 4.0

Photo: Duncan Wright, USFWS · Public domain

Photos and recordings are credited to their authors under the licence shown. Full profiles: Aleutian Tern and Sooty Tern.