NEST-SITE SELECTION BY MALLARDS AND BLUE-WINGED TEAL IN RELATION TO MICROCLIMATE

It is unclear whether female dudes select nest sites on the basis of m icroclimatic features. Therefore, we tested the nest microclimate sele ction hypothesis by concurrently monitoring temperature (T), solar ins olation, and relative humidity (RH) at Mallard (Anas platyrhynchos) an d Blue-winged Teal (A. discors) nest sites and nearby randomly selecte d ''nonnest'' sites (hereafter ''adjacent'' sites). Operative temperat ures (T-e) were calculated for nest sites and adjacent sites. Mallard and teal nest sites received consistently less insolation than adjacen t sites, but did not differ in T or RH. T-e at Mallard nest sites was more moderate than at adjacent sites; nest sites were cooler between 0 800 and 1730 CST. This pattern did not exist for teal nest sites, whic h had consistently lower T-e throughout daylight hours. Coefficients o f variation for all microclimatic variables did not differ between Mal lard and teal nest sites and adjacent sites. We examined interspecific differences in nest-site microclimate by matching data by date and st age of incubation. Teal nest sites received more insolation and experi enced greater T-e than concurrently monitored Mallard nest sites, but there were no interspecific differences in T or RH. Our results provid e only limited support for the microclimatic selection hypothesis, sug gesting that other factors are more important determinants of nest-sit e selection in ducks.