Resumen de Ecological, demographic and genetic constraints on the conservation of the globally endangered lear's macaw
Erica Cristina Pacífico de Assis
The Lear’s Macaw (Anodorhynchus leari) is endemic to the Caatinga biome (tropical dry forest in NE Brazil) and is listed as globally Endangered in the IUCN Red List. This species uses sandstone cliffs for breeding and roosting communally and feeds mostly on fruits of the Licuri Palm (Syagrus coronata). The whole global population is concentrated in two close localities, probably as the outcome of a large population decrease and range contraction in the past decades, but is currently sharply increasing. If the population does not expand geographically, the continuous increase could result in the saturation of environmental resources and generate negative density-dependent effects. We used a multidisciplinary research approach to investigate the population demography, potential genetic constraints and threats that may affect the conservation, recovery and expansion of this species. In Section 1 we provide the first estimates of breeding population size and the main breeding parameters for the species, through quantification and monitoring of active nests between 2009 and 2010 in the two breeding sites known until then, and estimated that c. 80% of the global population is constituted by non-breeding individuals. In Section 2 we estimate the recent population trend by employing a detection-based analysis, developing a binomial - negative binomial N-mixture model to estimate population size from replicated roost counts done by the Brazilian Environment Agency (ICMBio) from 2001 to 2014. Results suggest that population size is much larger than previously thought and that it increased 333% in that period. We also make recommendations for an improved design for population monitoring programs. Considering the past demographic history, potential genetic constrains in the remaining, although recently increasing population, are a concern. Therefore, in Section 3, we describe species-specific microsatellite primers developed from wild individual samples. Fifteen unlinked loci resulted informative for individual identification of related wild nestlings and could be applied for population genetics research. Then, in Section 4, we selected polymorphic microsatellites to genotype non-invasive samples (molted feathers) and estimate genetic diversity and effective population size across the current distribution range of the species. We found molted feather sample repetition (i.e. multiple feathers from single individuals), moderate levels of genetic diversity, and no evidence of strong inbreeding in any locality. Results also showed a wide genetic admixture among all localities and overall differentiation was low. The average adult sex-ratio based on non-invasive sampling is male-biased (0.61), underscoring the need for further research on the primary and secondary sex-ratios of the immature population. In Section 5, we describe our research on the current and historic distribution of the species, looking for the causes of local extinctions and the current threats that the population could be facing in an expansion process. By combining local knowledge (112 interviews) with field surveys, we located two recolonized breeding areas, a new communal roost, and another six areas from where the species disappeared. We also compiled past and current threats, assessed habitat traits in occupied and unoccupied areas, and finally developed habitat suitability models for the Lear’s Macaw and its main food resource (Licuri Palm). The overlap of these two models allowed identifying optimal areas for the range expansion of Lear’s Macaws, where future conservation actions should be concentrated. Given that the presence of invasive Africanized honey bees (Apis cf. melifera) was identified as a potential threat to Lear’s Macaws, in Section 6 we assessed the competition for cliff cavities used by nesting Lear’s Macaws and honey bees. We recorded > 100 honeybee hives in the Lear’s Macaw breeding sites, with a higher infestation in areas recently recolonized by the macaws. We treated hives with permethrin and, when feasible, we removed the comb and applied an insecticide (fipronil) to deter honeybee recolonization in the cavity. Our experimental hive treatments were effective, allowing nest recruitment and local population increase of Lear’s Macaws. We recommend intensive and continued Africanized honeybee hive eradication to enhance habitat restoration and facilitating Lear’s expansion into historical areas. The data generated by this thesis will be decisive for the design of management strategies aimed at the conservation of this endangered species.
