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Assessing Breeding Populations of Ducks by Ground Counts

by

Alex Dzubin

Introduction

Waterfowl inventories taken during the breeding season are recognized as a basic technique in assessing the number of ducks per unit area. That waterfowl censusing is still an inexact technology leading to divergent interpretations of results is also recognized. The inexactness stems from a wide spectrum of factors that include weather, breeding phenology, asynchronous nesting periods, vegetative growth, species present and their daily activity, previous field experience of personnel, plus others (Stewart et al., 1958; Diem and Lu, 1960; Crissey, 1963a). In spite of the possible errors, accurate estimates are necessary to our understanding of production rates of all North American breeding waterfowl. Statistically adequate censuses of breeding pairs and accurate predictions of young produced per pair still remain as two of the primary statistics in determining yearly recruitment rate of species breeding in particular units of pond habitats. Without precise breeding pair and production data, the problems involved in describing the reproductive potential of any species and its environmental or density-dependent limiting factors cannot be adequately resolved.

The purposes of this paper are to (1) describe methods used to estimate yearly breeding pair abundance on two study areas, one in Manitoba and the other in Saskatchewan; (2) assess the relative consistency, precision, and accuracy of pair counts as related to the breeding biology of duck species; and (3) recommend census methods that can more closely approximate absolute populations breeding in parkland and grassland habitats.

Scientific names of each duck species are from the A.O.U. Check-list (1957) except that both American widgeon and shoveler are considered species of Anas after Johnsgard (1965). Widgeon is used synonymously with American widgeon.

This resource is based on the following source: 
Dzubin, Alex.  1969.  Assessing breeding populations of ducks by ground counts.
     Saskatoon Wetlands Seminar.  Canadian Wildlife Service Report Series - 
     Number 6.  178-237pp.
This resource should be cited as: 
Dzubin, Alex.  1969.  Assessing breeding populations of ducks by ground counts.
     Saskatoon Wetlands Seminar.  Canadian Wildlife Service Report Series - 
     Number 6.  178-237pp.  Northern Prairie Wildlife Research Center Home Page. 
     http://www.npwrc.usgs.gov/resource/tools/duckcoun/duckcoun.htm
     (Version 07JAN98).

Table of Contents
Study Areas
Census Methods
Migration, Inventory, and Population Components
Duck Census Techniques
Appraisal of Factors Influencing Inventories
Recommendations for Block Study Area Census
Summary
Acknowledgments
Literature Cited
Discussion

Tables

Table 1 -- Size Distribution of Pond Basins, Acreage, and Shore-line Ditances of the Two Study Blocks al Full Supply of Water.
Table 2 -- Summary of Treatment Effects in Riparian and Upland Habitat.
Table 3 -- Sex ratios of ducks, 1956 to 1959, Kindersley Study Area.
Table 4 -- Seasonal changes in sex ratios of migrating lesser scaup, 1958 and 1959, Kindersley Study Area.
Table 5 -- Breeding pair estimates and species composition, Roseneath Study Area, 1952 to 1955.
Table 6 -- Breeding pair estimates and species composition, Kindersley Study Area, 1956 to 1959.
Table 7 -- Comparison of indicated pairs of diving ducks from ground census and observed nesting population.
Table 8 -- Seasonal census of mallards on Kindersley Study Area, 1958.
Table 9 -- Comparison of 1958 Kindersley census results utilizing various population comonents and sex ratio correction factors.
Table 10 -- Changes in five population components of mallards at five different periods during laying and early incubation.
Table 11 -- Mean population estimates of six dabbler species from five census periods: Walking census.
Table 12 -- Mean population estimates of six dabbler species from five census periods: Vehicle census.
Table 13 -- Census of six dabbler species on 3 days of the same week, Kindersley Study Area, 1959.
Table 14 -- Analysis of variation of dabbler counts taken at three different time intervals on 3 days.
Table 15 -- Yearly trends of indicated breeding populations of dabblers and ponds from mid-May ground counts.
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