Alejandro Salinas-Melgoza

Stability and change in vocal dialects of the yellow-naped amazon

Cultural evolution is an important force in creating and maintaining behavioral variation in some species. Vocal dialects have provided a useful model for the study of cultural evolution and its interactions with genetic evolution. This study examined the acoustic and geographic changes in vocal dialects over an eleven-year span in the yellow-naped amazon, Amazona auropalliata, in Costa Rica. Contact calls were recorded at 16 communal night roosts in 1994 and 19 roosts in 2005, with 12 roosts sampled in both surveys. In both surveys three dialects were found, each characterized by a distinctive contact call type and each encompassing multiple roosts. The limits between two of these dialects, the North and South dialects, was found to be geographically stable, while at the boundary between the North and Nicaraguan dialect there was introgression of each call type into roosts in the bordering dialect. Acoustic measurements and cross-correlations of spectrograms detected no change in the acoustic structure of contact calls in the South dialect but did show significant differences in the calls of both the North and Nicaraguan dialect between 1994 and 2005. These results are consistent with the vocal convergence hypothesis that proposes that dialects are long-term features maintained through some combination of biased transmission of local call types and purifying selection against foreign call types. Migration, copying errors and cultural drift may also play a role in the more subtle changes seen in the acoustic form of dialect call types.

Climatic variability, nest predation, and reproductive output of Lilac-crowned Parrots (Amazona finschi) in tropical dry forest of western Mexico

Abstract For 1996–2003, we determined reproductive output and success of 70 Lilaccrowned Parrot (Amazona finschi) nests in tropical dry forest of the Chamela-Cuixmala Biosphere Reserve in western Mexico. Only 42% of nests had young that fledged; predation was the main cause of nest failure. Low brood survival in 2000 and 2003 caused significant between-year variation in the probability of nest success during the nestling phase of the nest cycle. Reproductive output of Lilac-crowned Parrots was low, with females producing an average of 0.99 fledglings on an initial investment of 2.6 eggs. The fecundity component of clutch size varied significantly between years, because of the high median clutch size recorded in 2000. Nestling survival also varied significantly between years, creating large interannual fluctuations in reproductive output. The most productive breeding season was 1999, with an average output of 1.7 fledglings on an investment of 2.7 eggs; whereas the poorest breeding season was 2000, with an output of 0.57 fledglings from 3.3 eggs. Loss of reproductive potential was greatest in 2000 and 2003, because of brood reduction through starvation of later-hatched nestlings, with hatching order influencing the probability of nestling survival. Mean number of nestlings per egg-laying female was associated with interannual fluctuations in precipitation resulting from the El Niño-La Niña weather cycle in the Pacific Ocean. Both nest predation and food availability may limit parrot reproduction in tropical dry forests, with populations of threatened species in dry habitats being vulnerable to effects of climatic variability and habitat fragmentation.

Evidence for Vocal Learning and Limited Dispersal as Dual Mechanisms for Dialect Maintenance in a Parrot

Studies of avian vocal dialects commonly find evidence of geographic and acoustic stability in the face of substantial gene flow between dialects. The vocal imitation and reduced dispersal hypotheses are alternatives to explain this mismatch between vocal and genetic variation. We experimentally simulated dispersal in the yellow-naped amazon (Amazona auropalliata) by moving individuals within and across dialect boundaries in Costa Rica. One juvenile translocated across dialect boundaries altered its contact call to imitate the acoustic form of the local call six weeks post-release. In contrast, four adults translocated across dialect boundaries returned to their original capture site within 120 days, while five cross-dialect translocated adults who remained at the release site did not alter their contact calls. Translocated individuals were observed to show some segregation from resident flocks. The observation of vocal imitation by the juvenile bird supports the vocal imitation, whereas the behavior of adults is more consistent with the reduced dispersal hypotheses. Taken together, our results suggest that both post-dispersal learning by juveniles and high philopatry in adults could explain the stability of vocal dialects in the face of immigration and gene flow.

Factors Influencing Nest Spacing of a Secondary Cavity-Nesting Parrot: Habitat Heterogeneity and Proximity of Conspecifics

Abstract. Resource availability in a heterogeneous environment and density-dependent processes may influence the spatial distribution of individuals among habitats. The distribution of nests of secondary cavity nesters is rarely clumped because the birds are constrained by the distribution of existing cavities as nest resources. In this study, to evaluate the interplay of environmental and behavioral processes in the spacing of parrot nests, we compared the spatial distribution of active Lilac-crowned Parrot (Amazona finschi) nests with that of all cavities used as nests over 14 years. Parrots reused 42% of cavities, and the frequency of reuse was significantly associated with a previously successful nesting attempt. Positive fitness benefits of cavity reuse may indicate high-quality nest sites that are used more intensively by resident breeding pairs. Spatial-point-pattern analysis indicated that trees used as nests were significantly clustered within 60 m in the three nesting areas, with average distance of 100–200 m between nest trees. In a given breeding season, active parrot nests were separated by a mean 950 ± 890 m. Parrot nests were also located significantly closer to a tree used as a nest in the previous breeding season than the distance between nearest nesting conspecifics. This pattern suggests that conspecifics influence the spatial distribution of reproductive pairs breeding simultaneously, with nesting pairs occupying areas where suitable cavities are more numerous. The behavioral spacing requirements of nesting parrots may limit breeding densities and restrict management strategies to increase numbers of nesting pairs within protected areas.

SEASONAL VARIATION IN ACTIVITY PATTERNS OF JUVENILE LILAC-CROWNED PARROTS IN TROPICAL DRY FOREST

Abstract We used radio-telemetry techniques to determine hourly activity patterns of 29 juvenile Lilac-crowned Parrots (Amazona finschi) during 1996–2000 in tropical dry forest of Jalisco, Mexico. Parrots had two peak activity periods—early morning and late afternoon—for both overall activity and local movement. Individuals were generally inactive and did not change location for 5–6 hr during the middle of the day. Parrots were more active in the dry season than in the rainy season, although movements resulting in a change of location did not vary between seasons. Seasonal variations in activity of Lilac-crowned Parrots may be related to variations in food availability or temperature. Activity patterns of parrots need to be considered when evaluating habitat use or survey data.

Brood Sex Ratio of the Lilac-crowned Parrot (Amazona finschi)

Abstract Evolutionary theory predicts birds should adjust the sex ratio of their broods in response to external factors that differentially affect the reproductive value of each sex. We examined the brood sex ratio in the Lilac-crowned Parrot (Amazona finschi) in relation to climate, hatching date, and hatching order. We used polymerase chain reaction amplifications to identify the gender of 66 nestlings from 32 clutches spanning 7 years. There was a tendency to produce more female offspring in years of high nestling survival following high rainfall with a slight female-bias in third-hatched nestlings. We found no significant associations between brood sex ratio and rainfall, hatching date, or hatching order within clutches. Our results suggest the examined factors provide insufficient differential costs or benefits of offspring gender to promote sex ratio bias in this monomorphic species.

History of nonnative Monk Parakeets in Mexico

Nonnative Monk Parakeets have been reported in increasing numbers across many cities in Mexico, and were formally classified as an invasive species in Mexico in late 2016. However, there has not been a large-scale attempt to determine how international pet trade and national and international governmental regulations have played a part in colonization, and when the species appeared in different areas. We describe the changes in regulations that led the international pet trade market to shift to Mexico, then used international trade data to determine how many parakeets were commercially imported each year and where those individuals originated. We also quantified the recent increases in Monk Parakeet (Myiopsitta monachus) sightings in Mexico in both the scientific literature and in citizen science reports. We describe the timeline of increased reports to understand the history of nonnative Monk Parakeets in Mexico. As in other areas where the species has colonized, the main mode of transport is through the international pet trade. Over half a million Monk Parakeets were commercially imported to Mexico during 2000–2015, with the majority of importation (90%) occurring in 2008–2014, and almost all (98%) were imported from Uruguay. The earliest record of a free-flying Monk Parakeet was observed during 1994–1995 in Mexico City, but sightings of the parakeets did not become geographically widespread in either the scientific literature or citizen science databases until 2012–2015. By 2015, parakeets had been reported in 97 cities in Mexico. Mexico City has consistently seen steep increases in reporting since this species was first reported in Mexico. Here we find that both national and international legal regulations and health concerns drove a rise and fall in Monk Parakeet pet trade importations, shortly followed by widespread sightings of feral parakeets across Mexico. Further monitoring of introduced Monk Parakeet populations in Mexico is needed to understand the establishment, growth and spread of introduced populations.