Analysis of body condition of passerine birds in dry zones of the north of upper magdalena valley, colombia

Abstract

Body condition (BC) is a measure of the nutritional status of an animal represented mainly by the size of its energy reserves. In birds this condition is related with the biological fitness of the individual as it has effects on its behavior, reproductive success and survival. The aim of this study was to evaluate the BC of passerine birds in a Tropical dry forest fragment located north of the department of Tolima, Colombia, and analyze its seasonal and interannual changes over the years 2010-2014. The BC of 37 species was evaluated using the scaled mass index, which includes morphometric data such as wing chord length, tarsus length, total length, and body mass. The species that showed statistical differences in BC belonged to trophic groups Insectivore, Insectivore-Frugivore and Granivore-Insectivore. Interannual differences (P < 0.05) were found in the BC of Cyclarhis gujanensis, Sporophila funerea, Sporophila schistacea and Volatinia jacarina, and interseasonal differences in the BC of Camptostoma obsoletum, Euscarthmus meloryphus and Stelgidopteryx ruficollis. The only species that showed significant variations in both temporal scales were Sporophila minuta and Certhiaxis cinnamomeus. We concluded that BC varies significantly in some bird species on a seasonal or interannual scale and not globally in the Passeriformes assemblage. This variation is mediated mainly by the effects of precipitation on other ecosystem variables such as food availability, which is considered responsible for the energetic contribution and the weight gain of the individuals.