Abstract
Guans are large frugivorous birds that inhabit Neotropical forests and play a fundamental role in seed dispersal and forest regeneration. Despite their ecological importance, the natural populations of these birds are increasingly threatened by deforestation and hunting pressure. The present study was conducted in the Araripe National Forest, Ceará (Brazil), with the objective of estimating population parameters (density and total population size) in the Rusty-margined Guan (Penelope superciliaris) and the White-browed Guan (Penelope jacucaca), as well as providing data on their feeding ecology, including seasonal variation and fruit morphology. The study was based on the monthly collection of data between November, 2011, and October, 2012. Population parameters were estimated using line transect surveys, while feeding ecology was studied by direct observation, and the collection of plant and fecal samples. The estimated population density of P. superciliaris was 19.17 individuals/km2 (CV=13.98%), with a mean of 0.13 sightings per 10 km walked. Penelope jacucaca was not encountered during the surveys. A total of 14 plant species were recorded in the diet of P. superciliaris, 12 by direct observation, and two from fecal samples. Fruit diameter varied from 6.3 ± 1.35 mm (Miconia albicans) to 29.9 ± 1.7 mm (Psidium sp.). Yellow was the most frequent fruit color (41.6%, n=5), with two species each (16.6%) providing black, green, and red fruits. Fleshy fruits of the baccate (50.0%, n=6) and drupe (33.3%, n=4) types were the most consumed. The data on population parameters and feeding ecology collected in the present study provide an important database for the development of effective management strategies by environmental agencies for the conservation of the populations of the two guan species.
Highlights
The guans (Penelope spp.) represent the most diverse genus of the family Cracidae, with a total of 15 species (Sick, 2001)
The present study aimed to provide estimates of population parameters for P. jacucaca and P. superciliaris in the Araripe National Forest, as well as data on feeding ecology, including seasonal variation, and the morphometric characteristics of the fruits exploited by these species
Based on the Akaike Information Criterion (AIC), the Distance program selected the half-normal model as the best fit for the data (Figure 2), which provided an estimate of 11.66 groups per square kilometer, with a CI of 14.55-25.48 and CV of 13.98 (Table 1)
Summary
The guans (Penelope spp.) represent the most diverse genus of the family Cracidae, with a total of 15 species (Sick, 2001). The Rusty-margined Guan, Penelope superciliaris Temminck, 1815, is the smallest member of this family, and inhabits lowland rainforests, as well as other habitats, such as caatinga scrub, savanna woodland, secondary forests, and lake and river margins (Sick, 2001). As large-bodied frugivores, guans play a fundamentally important role in the regeneration of forests through seed dispersal, and are used as a subsistence resource by the rural and indigenous populations of the Neotropics (Rios et al, 2008; Bernardo and Desbiez, 2011; Bernardo et al, 2011) As they are able to ingest relatively large fruits, these birds help to disperse plants with large seeds that tend to be the most vulnerable to extinction due to the reduced diversity of frugivores capable of dispersing these seeds, especially in disturbed habitats. These birds may be essential for the maintenance of tropical forests (Silva and Tabarelli, 2000)
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