trinta-réis-boreal vs gaivina-de-nuca-preta

The Common Tern and Black-naped Tern can be distinguished primarily by their head markings. The Common Tern has a black cap that extends to the nape, while the Black-naped Tern features a distinctive black line running from the eye to the nape, creating a 'naped' appearance. Both species are similar in structure, but these head markings are key in identification.

Look for the black cap on the Common Tern compared to the black nape line on the Black-naped Tern. These head markings are the most reliable field marks to differentiate these species.

The Common Tern has a black cap covering the top of the head and extending to the nape. In contrast, the Black-naped Tern has a black line running from the eye to the nape, which gives it its name.