Effects of woody vegetation on prairie wetland birds

Bird surveys were conducted in wetlands (n = 1000) throughout South Dakota during the summers of 1995 and 1996 to assess effects of woody vegetation encroachment on nongame wetland bird species. Wetland bird species richness decreased as the extent of woody vegetation encompassing wetland perimeters increased. Logistic analyses indicated that four wetland bird species (Black Tern [Chlidonias niger], Wilson's Phalarope [Phalaropus tricolor], Eared Grebe [Podiceps nigricollis], Red-winged Blackbird [Agelaius phoeniceus]) were less likely to occur in wetlands surrounded by trees. The only birds using trees surrounding wetlands were edge species that thrive without the aid of management. We estimate that 35 560 wetlands in eastern South Dakota alone may have wetland bird populations which are negatively impacted by encroachment of woody vegetation. Wetland managers should consider limiting the extent of woody vegetation around prairie wetlands when nongame wetland bird production is the management goal.