Abstract
Land-use changes due to agricultural intensification and climatic factors can affect avian reproduction. We use a top predator of agroecosystems, the American kestrel (Falco sparverius) breeding in nest boxes in Central Argentina as a study subject to identify if these two drivers interact to affect birds breeding. We analyzed their breeding performance across a gradient of agricultural intensification from native forest, traditional farmland to intensive farmland. The surface devoted to soybean was used as a proxy of agriculture intensification; however, it did not affect the breeding performance of American kestrels. Even though the presence of pastures was important to determine the probability of breeding successfully. Climatic variables had strong effects on the species breeding timing, on the number of nestlings raised by breeding pairs and on the probability of those pairs to breed successfully (raising at least one fledgling). Our results highlight the relevance of pastures and grasslands for American kestrel reproduction. These environments are the most affected by land-use change to intensive agriculture, being transformed into fully agricultural lands mostly devoted to soybean production. Therefore, future expansion of intensive agriculture may negatively affect the average reproductive parameters of American Kestrels, at least at a regional scale. Further research will be needed to disentangle the mechanisms by which weather variables affect kestrel breeding parameters.
Highlights
Land-use changes due to agricultural intensification and climatic factors can affect avian reproduction
Soybean covered on average half of the surface of 500 m buffers around nest boxes in the intensive farmland area (IF) through the breeding seasons (2012 and 2014–2016) (Fig. 1), the surface ranged from 100% soybean cover in some nest boxes to less than 1% in others
Temperature conditions throughout the laying and chick rearing period affected the American kestrel breeding timing, the number of fledglings produced per nest and the probability of raising successfully at least one fledgling, while precipitation during November had a negative effect on their probability of breeding successfully
Summary
Land-use changes due to agricultural intensification and climatic factors can affect avian reproduction. We use a top predator of agroecosystems, the American kestrel (Falco sparverius) breeding in nest boxes in Central Argentina as a study subject to identify if these two drivers interact to affect birds breeding We analyzed their breeding performance across a gradient of agricultural intensification from native forest, traditional farmland to intensive farmland. Modern agricultural practices allowed this transformation even in traditionally marginal and unproductive areas expanding its impacts widely and into areas previously spared from a griculture[7] Given their naturally low abundances, large home ranges, and their position as top predators that may facilitate bioaccumulation processes, birds of prey may be sensitive to major ecosystem changes such as those produced by agricultural expansion and intensification[8,9]. Another example is the Western marsh harrier (Circus aeruginosus), a ground nesting raptor that use human constructed irrigation ponds for breeding in agricultural regions and exploit surrounding irrigated crops as hunting habitats where they find abundant r odents[17]
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