Investigations of Mallards overwintering at Calgary, Alberta

Abstract

Mallards (Anas platyrhynchos) were investigated intermittently from 1957 through 1967 to determine why they failed to migrate, and to test methods for controlling their numbers which increased from 2,000 in the early 1950's to a peak of 14,000 in 1964-1965. Band returns showed that most Mallards originated from breeding grounds north of Calgary and most returned there the following spring. More than one half of the direct band recoveries from Mallards transferred from Calgary to coastal British Columbia were made in Alberta and a significant fraction of survivors returned to Calgary the next winter. Data are given on sex and age ratios, weight trends, and the incidence of shot wounds. Available food, open water, and protection from hunting were considered the main factors causing Mallards to forego migration. Of the control methods tried (no supplementary feeding, removal by transfer, scaring with acetylene exploders, and winter shooting within the city), cessation of feeding was the most acceptable and efficient way to reduce numbers.