Evaluation of Indicated Breeding Pair Criteria to Estimate Mallard Breeding Populations

Abstract

Indicated breeding pair (IBP) criteria have been used since the 1950s to estimate breeding duck populations, yet few studies have evaluated these criteria for accuracy of population estimation. During spring aerial and ground surveys, observed pairs of ducks, lone males, and groups of 2-4 males are enumerated as IBPs, and assumed to reflect breeding pairs. We radiomarked and observed 36 paired and 44 unpaired male mallards (Anas platyrhynchos) in Manitoba in 1998 and Saskatchewan in 1999 to document their sociability and evaluate accuracy of IBP criteria. Paired male mallards occurred with their mates ≥54% of the time, whereas unpaired males occurred as lone males and in groups of 2-4 males 80% of the time from 21 April to 30 May. Based on these data, we calculated that mallard breeding populations in our study areas may be overestimated by approximately 7%. Inflated population estimates could promote underestimated production indices, overestimated fall population indices, and overly liberal harvest regulations. We suggest development of correction factors or modified survey criteria to improve accuracy of breeding population estimates for mallards and other duck species.