Masked Finch

Fairly small dark hummingbird, green overall with dark blue tail. Straight, medium-length bill. Sexes similar. Usually seen feeding singly in flowers along forest edge, shrubby second growth, and gardens. Separated from Emeralds by longer bill, blue-and-white vent, bronze patch on rump, and less deeply forked tail.

Bulky cold-brown seabird with white wing flashes. Usually seen singly in strong and direct flight, sometimes resting on the ocean with rafts of shearwaters. Chases gulls, large shearwaters, and even boobies, forcing them to regurgitate their food. Plumage overall rather plain, dark gray-brown, suggesting a muscular immature gull but with big white wing flashes, like the smaller, more lightly built jaegers. Often shows a pale blaze across the nape. Some birds have very pale blonde head and body. Breeds in Antarctica, further south than almost any other species of bird. Ranges across all oceans, mainly from March to October, typically staying offshore and very rarely seen from land. Compare with other skua species. In North Atlantic, Great Skua is warmer-toned, has a more capped or hooded appearance, and adults have golden spangles on upperparts. Separation from Brown Skua in Southern Hemisphere is more problematic; there are multiple populations of Brown Skuas and hybrids with South Polar are quite frequent! South Polar averages smaller-billed and slightly less bulky than Brown, and never has bold streaks or spangles on upperparts, but many birds are best left unidentified.

Very similar to Blue-and-white Flycatcher (breeding grounds do not overlap). Females and juveniles are essentially unidentifiable while on migration unless seen with an adult male, which is radiant, electric blue above and white below, lacking the contrasting black throat and breast of Blue-and-white, instead transitioning more smoothly from blue to white. Pale gray smudging on the flanks, while more difficult to see, can also serve to differentiate the two. Song is a thrush-like series of bright, slightly slurred warbles and whistles. Breeds in submontane mixed forests in northern China; wintering grounds little-known, but presumably at a similar altitudinal range in evergreen forests.