Social Nesting Behvior of the Bahama Parrot on Abaco Island and Its Conservation Implications

Nesting distributions of animals vary from isolated individuals to large colonies of breeding individuals and they can be influenced by numerous factors, including environmental conditions, relatedness and social interactions. Parrots are one of the most threatened orders of birds. Factors that influence their nesting success in natural habitat have been the focus of previous research. However, these past studies operated in systems limited in nest sites, which may also have influenced population dynamics. In contrast, the Bahama Parrot nests underground in abundant limestone solution cavities in the karst pine forest of Abaco Island, The Bahamas. This situation allows exploration of environmental and social factors that may influence nest success and breeding productivity without the limitation of the availability of nesting site resources. The objective of this study is to investigate the causes and consequences of semi-colonial nesting aggregations in the Bahama Parrot, addressing the influence of local habitat, relatedness of nesting neighbors, social behavior, and success of neighboring nests. The results of this information can be used in the management of habitat and parrot populations on Abaco Island, The Bahamas. The research was carried out on Great Abaco Island during the parrot breeding season (April - September) in 2010 – 2013. Nests were found by traversing logging roads. A number of ecological features were measured around nesting cavities and unused limestone cavities with the same dimensions as parrot cavities to identify favored characteristics. Nearest neighbors were identified for a subset of nests. Behavioral observations included time budgets of vocalization and movement to and from nests at focal and comparison nests (nearest neighbors and more distant nests) to determine if parrots were synchronizing behavior with close-nesting individuals. Predator simulations were conducted to elicit defense responses from focal and nearest neighbor nesting pairs. Using DNA collected from adults and chicks, I assessed whether spatially aggregated nests reflected kin clusters. Bahama Parrots on Abaco were distributed in aggregated spatial patterns in the nesting area. They nested in cavities found in more open areas. One contributing factor for the nest distribution was the uneven distribution of limestone cavities. Greater numbers of nests were found in areas with higher cavity concentrations. However, areas with high cavity concentrations but no parrot nests indicated that additional factors also were involved in concentrating nests in an area. Relatedness did not influence the aggregated nesting pattern. Close nesting neighbors were not more closely related than nesting individuals at other nest sites. No evidence of extra pair paternity was found within the small sample of nests that had full families sampled. However, genotypes of chicks raised in the same cavity in different years did provide support for the general belief that monogamous parrot pairs often reused the same nesting cavities over multiple years. Distances between neighbors had no effect on vocal synchrony. When a predator was introduced to a nest, the vocal response by the nesting pair and the nearest neighbor nesting pair increased, however no other behaviors provided nest defense. An effective defense against feral cats as predators was the predator control program carried out by the Bahamas National Trust. Nest success was higher in years with the predator control program underway. I did detect a relationships between nest success at a focal nest and its neighbor. Finally, I reviewed the taxonomic status of the Cuban parrot (Amazona leucocephala) complex. My review suggested that the two Bahama populations of the Cuban parrot (Amazona leucocephala bahamensis) should be classified as separate species (Amazona abaconensis and Amazona inaguanensis) and that the two Cuban populations should be a single subspecies (Amazona leucocephala leucocephala). These parrots use limestone cavities in the ground in open pine woodland as nest sites, and areas with higher densities of these cavities are used to a greater extent. As populations are expected to increase due to the success of a predator control program, sites with high cavity density are expected to be prime habitat for new nesting individuals. I therefore recommend the continuation of the prescribed burning to maintain the open understory that these parrots select. Furthermore, given the effectiveness of a current feral cat removal program in increasing nesting success, I recommend that predator control continue.