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Population dynamics of the Ruddy-capped nightingale thrush (Catharus frantzii) in the central highlands of Chiapas, Mexico Rangel-Salazar, José Luis

Abstract

I examined local population dynamics and regional distribution of the threatened Catharus frantzii (Ruddy-capped Nightingale Thrush) in the Central Highlands of Chiapas, Mexico. Pair density, nesting success and daily nest survival were higher in the moist forest habitat with more understory vegetation than in the dry-disturbed forest habitat. Nest-site selection and daily nest survival were associated with concealment attributes at the nest-site and patch levels. Parental visitation rates to nests did not differ across habitats, but were lower for successful than failed nests. Female nest attentiveness was higher in the moist forest and for successful nests than in the dry-disturbed forest and failed nests. Despite a higher carrying capacity for breeding pairs and captured individuals in the moist forest than the dry-disturbed forest, I found no variation in productivity (female offspring/breeding female/year) or adult survival (φ = 0.79) across habitats. Both survival (r = 0.93) and productivity (r = -0.33) correlated significantly with population growth (λ). Overall, both moist and dry forest types supported stable populations of C. frantzii (λ = 1.09), and thus I found no evidence for habitat-specific demography. In occupied forest habitats in the region around the Huitepec Reserve, C. frantzii showed a high probability of detection with repeated sampling. Abundance of singing males tended to be lower in younger and disturbed forest than in old-growth broadleaf forest. Habitat attributes such as elevation, slope, tree height, and shrub and herb densities varied across sites, but showed no consistent relationship to abundance. Although moist forests with more understory vegetation may favour better breeding success, adjacent dry-disturbed forests also supported stable, albeit lower, densities of C. frantzii in the Huitepec reserve. Both habitat types also supported non-territorial individuals that may be important contributors to stable populations. Thus, old growth and second-growth broadleaf forests with low to moderate vegetation harvesting can provide suitable habitats for C. frantzii in montane forests of the Central Highlands of Chiapas, Mexico.

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