Influência da fragmentação na condição corporal da comunidade de aves de sub-bosque em fragmentos de floresta tropical atlântica

Abstract

Body condition is a key indicator of individual health and fitness and is regulated by a combination of genetic and ecological factors. Birds are particularly interesting models for assessing body condition due to their great morphological and ecological diversity. However, the lack of standardization makes it difficult to determine the most appropriate parameters to evaluate this metric. Furthermore, environmental changes such as loss and fragmentation of habitats can change processes that affect the specific needs of species, causing a decrease in body condition, mainly due to a deficiency in the quality or quantity of nutritional resources. Therefore, in this study we used a scientometric approach to identify the main metrics, parameters and analyzes used to assess the body condition of birds. In addition to identifying the main ecological factors that influence these metrics. We evaluated a total of 316 articles. The main metrics used to assess body condition were "body mass" and "tarsal length", which can be influenced by a number of factors, such as abundance of food resources, weather period and environment. The most used analyzes were Linear Regression and Principal Component Analysis. The use of weight to estimate size is still the most implemented non-invasive strategy, with the length of a rigid structure usually used as a proxy for size. Then, in order to assess whether the body condition of bird communities in the Atlantic Forest of the Pernambuco Endemism Center tends to be higher in larger fragments and with better forest structure, as well as to test this variation in different precipitation regimes, the birds were studied in four protected areas in the State of Alagoas, Brazil. Body condition index (BCI) was calculated using a simple linear regression between mass and tarsus values. The significance of the difference in ICC values between the different fragments was tested using ANOVA and the variation in relation to the periods of the year using the t test. Landscape quality was assessed from forest structure through canopy cover, litter height and circumference with bark at breast height (CAP). When analyzing the ICC in the different fragments, a direct relationship with the size of the fragments was observed, in which individuals from the larger fragments obtained better mean body condition, however, no difference was observed in the condition between the different rainfall regimes analyzed. When we correlated the ICC values with the intrinsic characteristics of the fragments, gnificant values were observed for canopy cover and litter height, where fragments with greater canopy coverage and higher litter present a higher density of positive ICC values. On the other hand, the accumulated AP did not present significant values.