Elegant Tern
Thalasseus elegans
This is a medium-large tern, with a long, slender, slightly downcurved orange bill, pale gray upperparts and white underparts. It is 39–42 cm (15–17 in) long with an 76–81 cm (30–32 in) wingspan, and a weight of 190–325 g (6.7–11.5 oz). Its legs are black. From late summer to winter, the forehead becomes white. The black of the crest that comes down from the crown extends through the eye, creating a small black "smudge" in front of the eye even in winter plumage. On royal terns, the black crest stops at the eye, while lesser crested tern has a less shaggy crest.
ID text from Wikipedia, CC BY-SA 4.0
Greater Crested Tern
Thalasseus bergii
The greater crested tern is a large tern with a long (5.4–6.5 cm or 2.1–2.6 in) yellow bill, black legs, and a glossy black crest that is noticeably shaggy at its rear. The breeding adult of the nominate subspecies T. b. bergii is 46–49 cm (18–19.5 in) long, with a 125–130 cm (49–51 in) wing-span; weight 325–397 grams (11.5–14.0 oz). The forehead and the underparts are white, the back and inner wings are dusky-grey. In winter, the upperparts plumage wears to a paler grey, and the crown of the head becomes white, merging at the rear into a peppered black crest and mask.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
Learn this pair in BeakBrain
Photo and call practice, free in any browser.
Play BeakBrainPhotos and recordings are credited to their authors under the licence shown. Full profiles: Elegant Tern and Greater Crested Tern.