Effect of connectivity and habitat availability on the occurrence of the Chestnut-throated Huet-Huet (Pteroptochos castaneus, Rhinocryptidae) in fragmented landscapes of central Chile

Abstract

Although small isolated habitat patches may not be able to maintain a minimum viable population, small patches that are structurally isolated may be functionally connected if individuals can cross the gaps between them, in which case, their areas could be added to form a larger habitat patch, eventually surpassing the size threshold for holding a viable population. We studied whether models based on the size and isolation of habitat patches could be used to predict the distribution of the Chestnut-throated Huet-Huet (Pteroptochos castaneus) in fragmented landscapes of the coastal range of the Maule region, central Chile. We selected seven 10,000-ha landscapes (8.4-70.7% forest cover). For each habitat patch we made 18 predictions of the presence of the species based on the combination of two thresholds: three critical patch sizes for maintaining a viable population (62.5, 125 and 250 ha) and six critical isolation distances between patches (0, 10, 50, 100, 150 and 200 m). We used playbacks in 59 sampling points to estimate the species' presence/absence. We used logistic regressions to test whether the output of the patch-matrix models could explain part of the variation in the presence of Pteroptochos castaneus. The best predictions for the presence of P. castaneus were obtained with the most conservative scenarios (125-250 ha to 0-10 m), including a positive effect of the understory cover and a lack of effect of the forest type (native or exotic). Our findings suggest that the long term persistence of P. castaneus may depend on the existence of large and/or very connected forest tracts.