Factors affecting nestling body condition and pro-inflamatory response in American Kestrels in central Argentina

Factors determining body condition (BC) and pro-inflamatory response (PIC) in birds are complex. Agriculture intensification, with landscape homogenization and high pesticide use, is expected to produce low quality habitats for wildlife compared to more traditional productive systems or natural habitats. Breeding phenology and productivity may reflect the adjustment of breeding to seasonal conditions, competition between nestlings or parent quality. In temperate areas, precipitations can affect birds’ performance as they determine primary production and limit foraging possibilities. Here we evaluate the effect of land use, breeding parameters and precipitations in BC and PIC of American kestrel (Falco sparverius) fledglings in three areas in a gradient of land uses ranging from intensive agricultural lands to mixed productive systems and natural forests. We assessed BC of 968 nestlings in four seasons and measured PIC of 164 nestlings in a single season. Mixed generalized linear models were built with BC and PIC as response variables and land use, precipitations and breeding parameters as explanatory. BC of nestlings was lower in males and varied between seasons but not between areas. Larger clutch size and accumulated rain from August to October were associated with higher BC. However, brood size, cover of sunflower, cereals and stubble, and precipitations in November-December were negatively associated with BC. Although we worked in a gradient of agricultural intensification, no clear effect of it was found. The complex effects of land use, breeding parameters and precipitations that shape PIC and BC in American kestrels may be masking negative effects of agricultural intensification.