Habitat occupancy of the Dusky-legged guan in the lower delta of the Paraná River, Argentina

MALZOF, SILVINA LAURA; BOLKOVIC, MARÍA LUISA; THOMPSON, JEFFREY J.; QUINTANA, RUBEN DARIO

BIRD CONSERVATION INTERNATIONAL

CAMBRIDGE UNIV PRESS

Lugar: Cambridge; Año: 2013 vol. 23 p. 83 - 90

0959-2709

The Dusky-legged guan (Penelope obscura) is the southern most species of the family Cracidae, reaching its southern distributional limit in the delta of the Paraná River. Habitat loss, combined with uncontrolled harvest, has led to local-scale decreases or extirpation of the species, however,   no quantitative evaluation of habitat preferences has been made. We surveyed Dusky-legged guans in the Biosphere Reserve Delta del Paraná, Argentina along 543.9 km of 9 waterways by motorboat during both January and July 2009 and used occupancy modelling to estimate habitat and seasonal effects on occupancy. Detectability was 21 – 22% on average and occupancy estimates were highly variably within habitats, but highest in secondary forest, followed by mature plantation, and lowest in occupied residences. There were no significant differences in occupancy or detectability among habitats or seasonally. There was a strong positive effect of length of riparian habitat segments on occupancy and detectability.  Habitat management efforts should address increasing the suitability of mature plantation forest for guan by increasing their similarity to native forest in structure and composition. Furthermore, we illustrate that surveys by boat can be logistically affective for surveying cracids associated with riverine habitats and the importance to account for incomplete detectability since in our case failing to do so would have underestimated occupancy by 78 – 79% on average. Given this, the use of commonly accepted methodologies for surveying cracids that do not account for incomplete detectability should be reconsidered and methodologies that can produce robust, reliable estimates applied.