Rayane dos Santos Oliveira

The climate is expected to change substantially by the end of the current century. In response to climate change, species may disperse, adapt, or become locally extinct. We aim to assess how the climate changes predicted to occur by 2060 may affect the potential distribution of Tropical Mockingbird (Mimus gilvus antelius) and Chalk-browed Mockingbird (Mimus saturninus frater) within the Atlantic Forest domain, Brazil. Occurrence data for both species were compiled from the scientific literature and online biodiversity databases. A total of 118 georeferenced records were obtained for Tropical Mockingbird and 1080 for Chalk-browed Mockingbird. Species distribution models predicted that the two species would respond differently to the ongoing climatic changes. The Tropical Mockingbird will slightly expand its suitable habitat by 3.5% (3871 km²) under the optimistic scenario (minimum temperature increase by 2060; Representative Concentration Pathways-RCP 2.6) and 2.5% (2765 km²) in the pessimistic scenario (maximum temperature increase by 2060; RPC 8.5), relative to the 1960–1990 baseline. Chalk-browed Mockingbird will reduce its suitable habitat by 64% (70,780 km²) under RPC 2.6 and 65% (71,886 km²) under RPC 8.5. The two future climate scenarios suggest that sympatry between the two species will become increasingly rare, with a shift toward allopatry due to emerging climatically unsuitable areas separating their distributions. Our results highlighted the importance of environmental policies that incorporate local ecological contexts and species-specific traits to mitigate biodiversity loss under future climate conditions.

Congeneric species have similarities in phenotypic and ecological traits. The sympatry of congeneric species constitutes an opportunity for studies on coexistence. Two bird species of Mimidae, the native Tropical mockingbird, Mimus gilvus Oberholser, 1919, and the restinga invader Chalk-browed mockingbird, Mimus saturninus (Lichtenstein, 1823), currently occur in sympatry across the sandy-coastal ecosystem (restinga) of Espírito Santo state, Southeastern Brazil. We studied the spatial distribution of Tropical mockingbird and Chalk-browed mockingbird to understand the degree of competition across a preserved and urban gradient. We sampled 1,451 sampling units across a preserved and urban landscape in a coastal area of southeastern Brazil. The best-fitting model for abundance (Punctual Abundance Index) included urbanization index, distance from the coast, and distance from the closest protected area, which explained 63% and 97% of the abundance of Tropical mockingbird and Chalk-browed mockingbird, respectively. The species exhibited a segregated spatial pattern at small scale, indicating that both species are avoiding one another. Chalk-browed mockingbird showed ecological plasticity in modified environments, whereas Tropical mockingbird was more sensitive to urbanization. We suggested that the coexistence of these species is associated with resource partitioning. Monitoring Tropical mockingbird populations may be a proxy for the assessment of habitat quality and restoration success in the highly threatened restinga ecosystem.

Intraspecific aggressive behavior usually mediates competition for breeding and non-breeding resources among females and for mating opportunities among males. Variation in intrasexual aggressive levels across social and breeding contexts might then differ between sexes or converge due to different reasons. We studied three colonies of the polygynous Red-rumped cacique (Cacicus haemorrhous) during one breeding season. We evaluated whether the frequency of female-female and male-male aggressive interactions (number of interactions corrected by total number of individuals of the focal sex) varied with social context (total number of individuals of each sex in the colony) and breeding stage (number of nests under construction and nests with offspring) at each colony. We also tested for the occurrence (linearity and steepness) of a dominance hierarchy among banded males in one colony. We predicted positive correlations between female-female aggression and nests under construction (i.e. competition for nest sites) and between male-male aggression and nests under construction (a proxy for fertile females) and also male-male aggression and number of males (i.e. disputes for dominance rank) in the colony. We observed 533 female-female and 608 male-male aggressive interactions. Female-female aggressive interactions increased with the number of nests under construction in the colony, and decreased during incubation and nestling stages. Male-male aggressive interactions increased with the number of nests under construction, but not with the number of males in the colony. However, we found a steep and linear dominance hierarchy among males shaped by aggressive interactions. Our results suggest that (i) females behave aggressively when competing during the nest-building stage, probably for nest sites and materials; and (ii) male aggression determines the dominance hierarchy and is related to mating opportunities. HIGHLIGHTS ● We observed intrasexual aggressive interactions across breeding stages in a blackbird with female-only parental care.● Female-female and male-male aggressive interactions increased when nests were under construction in the colony.● Dominance hierarchy was evaluated for males and it was linear and steep.● Results suggest females compete for nest sites and male aggression shapes dominance and is associated with mating opportunities.