
89 
WATERFOWL POPULATION AND PRODUCTION TRENDS ON THE 
DELTA MARSHES OF SOUTH-CENTRAL MANITOBA - 1955 
S. Tenison Dillon 
Introduction 
This is a brief report concerning brood production and seasonal 
trends in waterfowl numbers ona large Manitoba marsh. 
Before my arrival on the study area in late June, aerial surveys 
were conducted by Charles Evans, U. S. Fish and Wildlife Service, Peter Ward, 
Delta Research Station, F. W. Martin, Utah State Agricultural College, and 
Carl Moran, Portage Flying Club, Portage la Prairie, Manitoba. Mr. Moran 
was my pilot on all subsequent surveys. The following persons assisted in the 
collection of brood data by motorboat transects: F. W. Martin, Peter Olson, 
University of Michipan, and D. F. McKinney, Delta Research Station. 
Population and brood data were collected by methods described in 
"Waterfowl Populations and Breeding Conditions - Summer 1954" - Wildlife No. 
27 (page 92). The following changes were made necessary by increased water 
levels: 
(1) The addition of about fifteen square miles of farm land, pasture 
and newly-formed marsh to the study area bringing the total area covered to 
approximately 59 square miles. This area was sampled by the addition of two . 
new transects and the extension of existing ones, The sample remained 25 
percent with two observers (12-1/2 percent with one), 
(2) The rejection of conversion factors applicable to the 1954 motor- 
boat counts due to changes in shoreline configuration. The calculation of new 
factors will necessitate the remapping of bay edges. 
Weather and Habitat Conditions 
Although spring weather was generally mild (resulting, for the first 
time in the station's history, in the arrival of all species of waterfowl except the 
white-winged scoter before April 15), several severe storms in early May and 
June brought water level fluctuations of a foot or more in 24 to 48 hours. The 
first of these (May 7) apparently destroyed many early nests in and around the 
marsh as was evidenced by the flocking of pairs and the late appearance of broods. 
Over-all water levels as of mid-July were one and one half feet above those of 
July, 1954. Although water levels decreased somewhat in August, they remained 
higher than fall levels of a year ago. 
