Ecology of the birds of the dry cloud forests of western Peru
Within the steppe-like western slope of the Peruvian Andes forest patches (dry cloud forests) occur from Ecuador to 13°S. Eight localities were studied between Huamba (4°41'S) and Zárate (11°55'S). A total of 145 bird species or 152 taxa (species and well marked subspecies) were recorded. The general distribution of the taxa supports the formerly discussed hypothesis that the majority of species arrived and colonised the western slopes from the north, but also suggests that eastern elements arrived to the western slopes south of the Porculla Pass (5°51'S), that some taxa evolved on the western slopes, and that southern elements complete the avifauna of the dry cloud forests. Six zones were identified as east-west exchange routes for birds. The northern origin of the majority of taxa is supported by three aspects, the marked diminution in species numbers from north to south; the pattern shown by 79% of the taxa suggesting a north to south dispersal of species along the slopes down to a limit determined by the humidity gradient and habitat conditions; and, the complex distribution patterns found in the Department of Ancash. Six main areas of taxa limits or replacement were identified that indicate that speciation processes on the western slopes have taken place mainly from ca. 7°30'S southward. The birds of the forests of central Peru consist of a mixture of permanent, seasonal, occasional and contaminant species. The avifauna is seasonal both in composition and abundance. Both are greatest from November to May and decrease to their lowest point in October. Insectivores and granivores are most abundant in May, frugivores in October and nectarivores show little annual variation. The main reproductive season in central Peru occurs in April and May.