Influence of Local and Landscape Characteristics on Avian Richness and Density in Wet Playas of the Southern Great Plains, USA

Playa wetlands (shallow, circular, depressional wetlands) in the Southern Great Plains are essential to the maintenance of regional biodiversity. However, the relative importance of habitat characteristics for maintaining avian species richness and density in playas is unknown. We examined influences of local- and landscape-scale characteristics on avian communities in wet playas. We conducted biweekly avian surveys on 80 playas (40 playas/year) from summer 2003 through spring 2005. Avian species richness was positively related to playa area and hydroperiod. More avian species and greater densities of birds were found at wetlands when water depths were intermediate (30-80 cm) during fall, winter and spring. Increased cultivation in playa watersheds increased total-, native-, and exotic-avian species richness. However, unsustainable sediment accumulation caused by cultivation can fill the playa basin and result in the loss of playa function, which will not benefit future bird populations. Landscape variables generally were less consistent with avian communities among seasons compared to local variables. Playas with greater numbers of other playas within 1 and 10 km had lower bird densities than those with fewer surrounding playas, likely due to the increase of habitat availability. Larger playas within predominantly uncultivated watersheds, that have an intermediate water depth, longer hydroperiod (within a season), and 26-50% vegetation cover are likely to maximize seasonal native avian richness. However, manipulating static water depths and maintaining long hydroperiods over extended periods will not meet avian objectives over the long term because playas must go through natural wet/dry fluctuations between years to maintain the desired plant community and productivity that supports diverse avian populations.