Occupancy Rate and Breeding Success of American kestrels in a Nest-Box Population in Central Argentina.

OROZCO, P. M.; GRANDE, J. M.

San Carlos de Bariloche

Conferencia; I Worldwide Raptor Conference (Raptor Research Foundation Annual Conference 2013 - III Neotropical Raptor Network Conference - WWGBP VII International Conference on Birds of Prey and Owls); 2013

CRUB-Universidad Nacional del Comahue; Neotropical Raptor Network-The Peregrine Fund; World Working Group On Birds Of Prey And Owls; Raptor Research Foundation

In the last decades agricultural intensification processes have caused strong environmental changes. This has negatively affected many species, including top predators as birds of prey.  To analyze these effects in a population of American kestrels (Falco sparverius) in La Pampa, Central Argentina, we placed nest boxes in three different areas: 1) a natural Caldén forest (Prosopis caldenia) (twenty four boxes remnant of fifty placed in 1998; 2) a traditional farming area (forty nine boxes placed in 2011; 3) an intensive farming area (thirty boxes placed in 2012).  Here we present preliminary data on occupancy rates and breeding success.  Occupancy rates were very high in agricultural areas (65% in 2011-12 and above 80 % in 2012-13) contrasting with a long-lasting low occupation rate in the forest area (lower than 25 %).  The mean laying date was within the last week of October in both seasons although it was a week earlier in 2012-13 for the areas one and two. In the second season laying date was significantly later in area three where the boxes were ready a week later.  Clutch size was similar in the three areas and the two seasons (mean around 4.25).  The proportion of pairs breeding successfully tended to be lower in 2012-13 although not significantly.  The number of fledglings per breeding pair was significantly lower in 2012-13, whether including area three in the analysis or not. Besides laying date, no differences were found among the three areas although clearly a more accurate estimation of habitat characteristics around each box would be desirable for robust conclusions.  The extremely high occupancy rates and good reproductive values confirm that Argentinean agricultural lands provide excellent habitat for the American kestrel.