Breeding strategies of passerines in the world’s southernmost forests
Date
2018
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Abstract
Species with wide breeding ranges have evolved different breeding strategies at different latitudes. Most passerines breeding in the South American temperate forest biome (30-55 S) have wide breeding ranges; however, most studies have been conducted in its northern region (30-42°S). Here for the first time, and during three breeding seasons (2014-2017), we monitored 102 nests of the five most abundant open-cup forest-dwelling passerines in the Cape Horn Biosphere Reserve, Navarino Island (55°S), southern Chile. Additionally, we compared the breeding strategies of the Austral Thrush (Turdus falcklandii) to other breeding populations at lower latitudes (33°S and 39°S). Most species started laying eggs the last week of September. The White-crested Elaenia (Elaenia albiceps) started breeding two months later. The Tufted-tit Tyrant (Anairetes parulus) was the most specialized in terms of nest substrate and Turdus the least. We found that Turdus had larger clutch sizes and nested closer to the ground on Navarino Island than the northern populations. The difference in clutch size corresponds with the described pattern of larger clutch sizes at higher latitude, and for species nesting on islands. The difference in nest height from the ground could be attributed to evolution in the absence of ground predators on Navarino. This behavior, however, could put them at a higher risk of predation by a recently introduced mammalian predator, the American mink (Neovison vison). By better understanding the breeding biology of these species, further research can be conducted to understand differences in breeding strategies among populations and factors affecting breeding success