BREEDING SEASONS IN THE GALAPAGOS.

Abstract

Summary. The Galapagos are on the equator. In the cool and cloudy dry season the south‐east trade wind blows and the cold Humboldt current flows strongly round the islands. In the rainy season, which is very variable but usually lasts from about January to April, the weather is calm, warm and sunny, with periodic heavy rain, while the northern boundary between the Humboldt current and the warm Pacific drift is further south, in some years south of the Galapagos. Captive Geospizinae are capable of breeding throughout the year, but in the Galapagos these finches, like the other passerine birds, breed only in the rainy season. Rain appears to stimulate their sexual behaviour. Some abnormal breeding in September 1906 is discussed. The dove starts and stops breeding about two months after the passerine birds, but mainly overlaps with them, in March and April. The hawk and short‐eared owl have young in the cool dry season after the rains, as do large raptors in Africa. The duck and the herons breed in the rainy season, but also in August and September. Many species of sea‐birds breed nearly throughout the year, but five of the six Procellarii have their young in the cool dry season when the Humboldt current flows most strongly round the islands. The gull Larus fuliginosus breeds about November, i.e. at a different season from, all other Galapagos birds (including the other species of gull), but at the same season as the related L. modestus on the adjacent mainland of South America.