Pond Characteristics and Occupancy by Red-Necked Phalaropes in the Mackenzie Delta, Northwest Territories, Canada
Red-necked phalaropes (Phalaropus lobatus) breed in Arctic and Subarctic lowlands throughout the circumpolar region. They are highly reliant on shallow freshwater ponds for social interaction, copulation, and foraging for small aquatic invertebrates. Threats related to warmer continental temperatures could lead to encroachment of shrub vegetation and premature drying of wetlands that serve as breeding habitat. We documented patterns of pond use over the breeding season and investigated pond characteristics associated with high occupancy by red-necked phalaropes. Research was conducted during two breeding seasons in a large wetland on Niglintgak Island, located in the mouth of the Mackenzie Delta, Northwest Territories. The frequency of pond occupancy declined between the onset of incubation and average hatch dates. Neither invertebrate assemblages (potential prey) nor physical characteristics (water chemistry and vegetation characteristics) varied significantly between ponds categorized as high-use, low-use, and no-use, in either year. Dry weight of potential prey (g/m3) was higher during the incubation period than during the nest initiation period. Pond occupancy both prior to and during incubation showed a clumped distribution, suggesting that choice of ponds was related in part to social stimulation. Future studies should examine the proximity of ponds to nest sites, the effects of premature drying of ponds on food availability, the distribution of resources surrounding ponds, and the occupancy of ponds by broods during the period preceding fall migration.