South American Tern vs White-fronted Tern

South American Tern

Sterna hirundinacea

Medium188 gMarine

With adult South American terns reaching a length of 40 to 44 centimetres (16 to 17 in), they are larger than either common terns (Sterna hirundo) or Arctic terns (Sterna paradisaea). Otherwise they closely resemble these species in plumage at all times of year. The beak is larger and is red in adults, and they do not have a dark-coloured bar on the carpus of the wing. The black cap extends below the eye, usually separated from it by a white crescent, and the rear edge of the cap is neatly defined.

ID text from Wikipedia, CC BY-SA 4.0

Photo: Chris Pearson from Leuchars, Scotland · CC BY 2.0

White-fronted Tern

Sterna striata

Medium129 gCoastal

The white-fronted tern is an average-sized tern; its dimensions are 35–43 cm (14–17 in) in length, with a wingspan between 79 and 82 cm (31 and 32 in); the male weighs on average 130 g (4.6 oz). Females are marginally smaller than males, but this is difficult to determine when observing individuals in the wild. Breaking down their monochromatic colouring, the white-fronted tern's lightest features are its all-white body, tail and underwing, with the upper side of the wings a light silvery-grey hue. Voice: A very dull crek is used in courtship when the male is flying above groups, individuals may respond with the same noise. When descending upon intruders, they will let out a continuous keark. Generally calling between individuals is a high-pitched siet used frequently during flight, it will be repeated over and over in particular intervals.

ID text from Wikipedia, CC BY-SA 4.0

Photo: Joe Dillon · CC BY 4.0

Photos and recordings are credited to their authors under the licence shown. Full profiles: South American Tern and White-fronted Tern.