Diversity, biogeography, abundance, and conservation of the birds of Mocha Island National Reserve, Chile

Abstract

The avifauna of Mocha Island is analysed according to species richness, habitat use, and reproductive status, and the first quantitative population estimates of forest landbirds are presented basing on unbiased survey data as a basis for conservation. We recorded a total of 100 species, including non-breeders. Among all recorded taxa, landbirds (n = 48 spp. or 48 %) exhibit higher species numbers when compared to shore- and seabirds (38), and freshwater birds (14). Within the documented breeding avifauna (n = 54 spp.) landbirds take an even relative higher value, amounting to 88 % (or 42 spp.). Austral and Neotropical species are most numerous within the landbird assemblage, reflecting the closest biogeographical realm. When comparing different Chilean avifaunas, southern mainland ecosystems show the highest landbird richness (90), followed by Chiloe Island (61), Mocha Island (42), and remote Juan Fernandez Islands (11). From line transects surveyed, 884 bird individuals belonging to 18 resident forest landbird species were recorded (averaging 10.3 ind/ha). We calculated the total population size of forest landbirds in the reserve (2300 ha) being 23,681 individuals. Two of the three endemic taxa (Mocha Rayadito and Mocha Chucao) show relatively high population sizes of about 4,100 and 3,700 individuals, respectively. The Mocha Thrush shows a population of about 670 individuals in forests, but is equally abundant in anthropogenic pastures around. Future conservation management of Mocha Island should consider richness, composition, and abundance of landbirds reported in this study, with emphasis on breeding ecology of the three mentioned endemics. Priority should be put on controlling illegal timber extraction, bird hunting and chick collecting, as well as on sensitization of local people to avoid introducing alien species.