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Population Demographics and Breeding Ecology of the Long-tailed Duck (Clangula hyemalis) in the Churchill, Manitoba Area

Matthew C. Perry 1 and Robert M. Alison 2
1USGS, Patuxent Wildlife Research Center
12100 Beech Forest Road, Laurel, MD 20708, USA
28 Mile Point RR 1 Orillia, Ontario L3V 6H1

ABSTRACT

The population demographics and breeding ecology of long-tailed ducks (LTDUs; Clangula hyemalis) are being studied in the Churchill, Manitoba area and data are being compared to data collected 30 years ago. This area is unique in that there are numerous nesting ducks, is readily accessible to researchers, and represents the most southern known breeding population of long-tailed ducks. LTDUs on the 4000 ha study site were captured during a two-week period in mid-June 2005 with mist nets set over water. In addition, females were captured while nesting in August 2005 with the use of a long-handled dip net. In June and August a total of 51 LTDUs were banded and sex ratio was equal among after hatching year adults and hatching year young. However, no second year males were captured in June, although second year females were common on breeding site. During June 2005, a total of 15 nests were discovered and mean clutch size was 7 eggs. Number of discovered nests in 2005 was approximately half the number found during initial work in 2004. Several nest starts (1-2 eggs) were discovered, but eggs disappeared within a few days apparently from herring gull (Larus argentatus) predation. This study revealed the close association of LTDUs and common eiders (Somateria mollissima) and arctic terns (Sterna paradisaea), which nest simultaneously and in the same habitat. Both species seem to benefit LTDUs by reducing predation by herring gulls, whose numbers are increasing in the study area. The use of islands or narrow peninsulas as nesting sites for ducks and terns was an important characteristic of nesting sites that might have potential benefits from reduced predation. Understanding the Churchill population of LTDUs could have important implications in understanding populations in more remote areas.

Alison surveying Churchill, Manitoba area

BACKGROUND

Little is known about the current population demographics and breeding ecology of long-tailed ducks (Clangula hyemalis) in the Churchill, Manitoba area, although extensive work was conducted 30 years ago by Dr. Robert Alison. Increased knowledge of these factors will result in better population management for this species and seaducks in general, which are in need of more study. Population surveys conducted on the west coast of North America suggest drastic declines for the long-tailed ducks and there also is concern of wintering populations on the Atlantic coast. In many areas of its range there also is a disparate sex ratio that favors males. This study is collecting data on the population demographics of long-tailed ducks in the Churchill area as well as accumulating data on the nesting habitat, on which this population is dependent. The Churchill, Manitoba study site is unique in that there are numerous nesting ducks, is readily accessible to researchers, and represents the most southern known breeding population oflong-tailed ducks.

The habitat surrounding the areas used for nesting or loafing was evaluated to determine biotic and abiotic factors important to the ducks using the area. The diversity and abundance of macro-invertebrates available for food for ducklings and adults are important factors in understanding optimum habitat for this species. The use of islands as nest sites was evaluated as a potential factor reducing predation.

Data are being compared with historic data collected at this study site, and are being used as the basis of future studies, possibly with satellite radio telemetry that will have more of a continental perspective to the Churchill population. This study is also providing information on common eiders (Somateria mollissima) and arctic terns (Sterna paradisaea), which nest simultaneously and in the same habitat. Population biology is considered to be the largest gap in our knowledge in the life history of long-tailed ducks. This pilot study is trying to fill that gap by providing information on a breeding population of long-tailed ducks that will include nesting chronology, productivity, brood survival, and intra-specific interaction.

 

OBJECTIVES

The goals of this pilot study are to determine components of breeding ecology of the local Churchill group of long-tailed ducks (LTDU) and to compare current status of long-tailed ducks and their habitat at Churchill with data collected by Dr. Alison thirty years ago. These data are providing baseline information that might have important value for long-term changes (e.g., global warming) that might be occurring in the Churchill area and throughout northern North America. Specific objectives include:

1. Determine nesting chronology and productivity of long-tailed ducks at the Churchill study site.

2. Develop a population of marked ducks and methods of marking to enable more detailed
study of demographics.

3. Determine intraspecific relationships and habitat conditions that affect nest location and outcome of nesting activity.


TECHNIQUES

Long-tailed ducks on the 4000 ha study site near Churchill, Manitoba were captured during a two-week period in mid-June with mist nets set over water, which were monitored continuously to avoid injury of ducks. In addition, females were captured while nesting with the use of dip nets. All nest examination and trapping was conducted late in incubation to minimize the possibility of nest desertion. Success or failure of all nests was determined by presence of embryo sacs detached from the eggshell. Size of broods was determined at hatching. Broods were drive-trapped into mist nets above and below water in early August to capture young of the year and molting females to determine brood survival.

All captured long-tailed ducks were banded with USGS-issued bands, and were aged, sexed, and weighed before release at capture site. Ducks were aged by use of bursa depth and plumage characteristics (especially scapulars, remiges, and retrices). The location and number of any eiders observed during this study were recorded for potential future studies with this species. Eiders are believed to be increasing dramatically since the 1960s and also are believed to winter on Hudson Bay. Intraspecific relationships in the study site was determined by recording all other avian species associated with the nesting site of the long-tailed ducks. Distance between nests, clutch size, and any intraspecific activities were recorded

Each nesting site was recorded as being on an island, peninsula, or mainland. The habitat around each site used for nesting was described using biotic and abiotic characteristics, including elevation of nest above water, distance of nest from water, size of island, and distance from human influence (e.g., road). Vegetation surrounding each nest was identified and percent cover for each plant species was estimated in the 2-meter area around each nest.

Dr. Perry seen here retrieving long-tailed ducks from mist net.
Dr. Perry seen here retrieving long-tailed ducks from mist net.

Female long-tailed duck captured while nesting with the use of a dip net.

Female long-tailed duck captured while nesting with the use of a dip net.

RESULTS

During June 2005, a total of 15 nests were discovered and mean clutch size was 7 eggs. Number of discovered nests in 2005 was approximately half the number found during initial work in 2004. Several nest starts (1-2 eggs) were discovered, but eggs disappeared within a few days apparently from herring gull (Larus argentatus) predation. Numbers of this species have increased in recent years in LTDU nesting areas. LTDU nests were located an average 2.2 m from the water edge and 31 cm above water surface. Mean bowl depth late in incubation was 5.9 cm.

In June and August a total of 51 LTDUs were banded and sex ratio was equal among after hatching year adults and hatching year young. However, no second year males were captured in June, although second year females were common on breeding site.

Previous studies on the Churchill site by both principal investigators have revealed the close association that long-tailed ducks have with common eider and arctic terns. Arctic terns are very aggressive to predators such as gulls. Special consideration was given in this study to determine the commonality of factors in regard to nesting sites for these three species. The use of islands or narrow peninsulas as nesting sites for these species was evaluated as an important characteristic of nesting sites that might have potential benefits from reduced predation.

 

Dr. Perry seen here weighing a female long-tailed duck.
Dr. Perry seen here weighing a female long-tailed duck.
Dr. Perry seen here preparing to band 2 common eiders.
Dr. Perry seen here preparing to band 2 common eiders.
A long-tailed duck nest.
A long-tailed duck nest.
Dr. Perry seen here measuring the nest's distance from the water.
Dr. Perry seen here measuring the nest's distance from the water.

CONCLUSIONS

This study is a preliminary study that is being used as the basis for future studies using the Churchill population for a continental approach with this species. Island nesting seems important to reduce mammalian predation, but does not seem to deter herring gull predation. Arctic terns do deter gull predation, although numbers of each species is probably an important variable. Understanding the Churchill population of long-tailed ducks could have important implications in understanding populations in more remote areas.

Colonial nesting of common eider with Canada goose.
Colonial nesting of common eider with Canada goose.

ACKNOWLEDGMENTS

This study was supported by the Churchill Northern Studies Centre (CNSC) Research Fund and U.S.G.S. Photographs were taken by Caroline Bond. Alicia Berlin, Marie Brady, David Kidwell, and Edward Lohnes provided technical assistance.

Churchill Northern Studies Centre (CNSC).
Churchill Northern Studies Centre (CNSC).
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