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

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

Bariloche

Congreso; I Worldwide Raptor Conference; 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 causedstrong environmental changes. This has negatively affected many species,including top predators as birds of prey.  To analyze these effects in apopulation of American kestrels (Falco sparverius) in La Pampa, CentralArgentina, we placed nest boxes in three different areas: 1)a natural Caldén forest (Prosopis caldenia) (twenty four boxes remnantof fifty placed in 1998; 2) a traditional farming area (forty nine boxes placedin 2011; 3) an intensive farming area (thirty boxes placed in 2012).  Herewe present preliminary data on occupancy rates and breeding success. Occupancy rates were very high in agricultural areas (65% in 2011-12 andabove 80 % in 2012-13) contrasting with a long-lasting low occupation rate inthe forest area (lower than 25 %).  The mean laying date was within thelast week of October in both seasons although it was a week earlier in 2012-13for the areas one and two. In the second season laying date was significantlylater in area three where the boxes were ready a week later.  Clutch sizewas similar in the three areas and the two seasons (mean around 4.25).  Theproportion of pairs breeding successfully tended to be lower in 2012-13although not significantly.  The number of fledglings per breeding pairwas significantly lower in 2012-13, whether including area three in theanalysis or not. Besides laying date, no differences were found among the threeareas although clearly a more accurate estimation of habitat characteristicsaround each box would be desirable for robust conclusions.  The extremelyhigh occupancy rates and good reproductive values confirm that Argentineanagricultural lands provide excellent habitat for the American kestrel.