Ecologia reprodutiva, ocupação e rede de associação em Cyanocorax cyanopogon (aves, Corvidade)

Abstract

Although costly, group living is widely distributed in nature. Among birds, jays and crows (Corvidae) stand out for their cognitive ability and for forming social groups that provide better performance in caring for offspring. Cyanocorax cyanopogon (White-naped Jay) is a corvid endemic to Brazil and occurs mainly in the Caatinga and Cerrado biomes, both with a strong seasonal component, alternating between periods of low and high productivity. To understand the strategies used by these birds to live in these biomes: 1) we used data from citizen science and circular statistics to verify if they adjust their reproduction to the availability of resources in the environment; 2) we used a probabilistic multimodel approach to test if environmental characteristics and resource availability interfere in their occurrence and size of home range in a Caatinga area; and 3) we used a social animal network approach to analyze the association networks of individuals at the area of FLONA-Açu. In our nest records we found that the development of the nestlings lasts about 5 months, from the time of nest construction until the nestlings have acquired adult plumage. Putting our breeding records together with those available on Wikiaves and comparing them with the Worldclim precipitation data, we found that most of the records anticipate the month with the highest rainfall. We also found that this trend is stronger in the Cerrado than in the Caatinga. We compared 64 models generated from our global model with environmental variables. Of the total, 4 models were the most representative. The most relevant variables for occupancy were: season, distance from headquarters and NDVI. In this model the occupancy estimate for the rainy period was almost half of what was observed in the dry period. Occupancy also varied positively as a function of NDVI and negatively as a function of distance from headquarters, both with greater effect in the rainy season. We captured and ringed 89 individuals at the headquarters of the Açu National Forest. We built three association nets with 72 individuals captured and banded during the three years of the study. We found that the dry season net had a larger number of individuals and a more intense pattern of interactions than the rainy season net. We also saw that despite the variation in the number of individuals, the individual values did not vary much between the seasons. We also found that the association between the observed individuals remained consistent over time.