On the ecology and conservation of the critically endangered Másafuera Rayadito (Aphrastura masafuerae)

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Ornitologia Neotropical




The Masafuera Rayadito (Aphrastura masafuerae) is a little known, critically endangered, endemic bird species of Alexander Selkirk Island, Juan Fernández Archipelago, Chile. The last assessment reported a population as low as 140 individuals. Possible causes for its decline could be habitat loss and degradation, and potentially a lack of nest sites. We conducted a new population assessmentusing point counts and investigated habitat use patterns during the post-breeding season of 2006 and 2007. We also installed 81 nest boxes (in three areas) to study the species’ breeding ecology and to increase potential nest sites. Our estimated mean rayadito abundance for 2006 was 0.54 ± 0.19 ind/ha(mean ± SE, approximately 250 individuals in the southern area). We could not survey all the areas where the rayadito might be found, but extrapolating to a conservative estimate of potential habitat of1000 ha we estimate a total population size of 500 individuals (148–932, CI 95%). We found a significant positive relationship between number of rayaditos and canelo (Drymis confertifolia) cover (GLM Poisson, P= 0.045), with canelo coverage approximately 8% of the southern area. A year after establishment, seven out of 42 boxes (southern group) had been occupied: three complete and four incomplete nests. All three complete nests had a supporting structure (1042.99 ± 18.16 cm3) of canelo and tree-fern (Dick-sonia externa) rootlets and a soft cup (313.68 ± 112.08 cm3) of petrel (Pterodroma externa and P. longi-rostris) feathers. Our results showed rayadito population levels similar to what was found in the late1980s, although the species still faces considerable threats. The probability of box occupation was not affected by tree diameter or box placement height. These results suggest that canelo trees and nest boxes could be used in the restoration of the rayadito habitat