USE OF BOREAL FORESTED WETLANDS BY PACIFIC LOONS (GAVIA-PACIFICA LAWRENCE) AND HORNED GREBES (PODICEPS-AURITUS L) - RELATIONS WITH LIMNOLOGICAL CHARACTERISTICS

Our objective was to determine if the occurrence and abundance of Paci fic loons (Gavia pacifica Lawrence) and homed grebes (Podiceps auritus L.) on 123 wetlands of Yukon Flats National Wildlife Refuge in east c entral Alaska were related to the limnological characteristics of thos e wetlands. Aquatic bird-wetland use surveys were conducted in conjunc tion with limnological sampling from May through September 1985-87 and May through August 1989. Results from logistic regression analysis de monstrated a significant association between the probability of wetlan d use by Pacific loons and shoreline length, water color, calcium and total phosphorus. Wetland use by horned grebes was related to shorelin e length, pH, and chlorophyll. Aquatic bird abundance was then used as a Poisson response variable and modeled as a function of wetland limn ological characteristics. Our results indicate that Pacific loon abund ance was adequately modeled by linear and quadratic functions of shore line length, color, pH, calcium and total phosphorus. Homed grebe abun dance could not be modeled with this approach. The statistical techniq ues known collectively as generalized linear models provided a framewo rk for the development of models for aquatic bird use of wetlands. Our results, however, indicate that while this approach shows promise, a better understanding of how to model aquatic bird abundance is needed. We then identify problems in model development and suggest avenues fo r future research.