Managing the Black Duck

by: Randy Milton

The American black duck is one of our most sought after waterfowl by hunter and non-hunter alike. It breeds in low densities throughout eastern North America, but winters primarily in the coastal states of the Atlantic Flyway from Maine through Virginia. Smaller numbers winter in the states of the Mississippi Flyway. About 12,000 to 13,000 black duck live along Nova Scotia's coast each winter.

Until recently, the only information available on the status of the black duck was derived from the Midwinter Waterfowl Survey (MWS). Conducted every January since 1955, the survey provides an index of population trends rather than a population estimate. The number of black ducks recorded during this survey has declined since the early 1960s (Figure 1).

In the early 1980s, concern over this decline resulted in court action filed by the Humane Society of the United States, the Maine Audubon Society, and Jown W. Grandy. This action identified the inadequacy of previous data collection programs to properly evaluate the reasons for changes in black duck numbers. During the last 10 years, actions have been taken to address this concern.

As a result of the court action, restrictive harvest regulations in both the Atlantic and Mississippi Flyways were started in 1983. Attempts to reduce the harvest of black duck in Canada began in 1984 with restrictive seasons, and bag and possession limits. The objective of these actions was to halt the population decline and hopefully stimulate a recovery.

Nova Scotia reduced its daily bag limit from 6 to 4 in 1984. The season was shortened in 1989, opening a week later and closing two weeks earlier in coastal waters. This change was recommended to reduce harvest pressure on birds breeding in Prince Edward Island, Newfoundland, and Nova Scotia.

Canadian hunters have liberal regulations compared to the Americans. Nova Scotia has one of the longest seasons (extending over 85 contiguous days) and highest bag limits (daily limit of four and possession of eight). The bag limit for black duck in the U.S. flyways is restricted to one bird per day, with a possession limit of two. Waterfowl hunting is limited to only 30 days.

Canada has reduced its harvest by nearly 20 per cent during the restrictive period 1984 to 1991, compared to the 1978 to 1982 period. In comparison, harvest restrictions have had more impact in the U.S. The harvest was reduced more than 40 per cent in both flyways during the restrictive period 1983 to 1992 compared to the 1977 to 1981 period.

Nova Scotia reduced its harvest by approximately 25 per cent between the two periods (Figure 2). A large part of this decline can be attributed to fewer waterfowl hunters in the province. The number of hunters peaked at 16,297 in 1978-1979, and has declined an average 4.1 per cent each year to 8,740 (preliminary total) in 1993-1994.

Have these restrictions made an impact on the number of black duck? Waterfowl banding is a valuable management technique used to estimate harvest pressure and population survival rates. A preliminary analysis and evaluation of band recoveries was conducted to determine if recovery and survival rates differed during liberal (1978-1981) and restrictive (1984-1991) hunting seasons. The analyses showed a significant decrease in recovery rates, but no significant change in survival. A decrease in harvest rates did not translate into increased survival of birds into the next breeding season. The lack of change in survival rates with a reduction in harvest rates may be related to factors other than hunting. A detailed analysis of the banding data is being conducted with input from federal, provincial, and state representatives of both countries.

Since about 1980, the rate of decline in the black duck population index recorded by the MWS has appeared to level off (Figure 1). This is believed to be a result of restrictions placed on the harvest in Canada and the U.S. The results of the 1993 survey indicate that the population index was up 5 per cent from 1992, but still down -2 per cent from the 1983-1992 average. Over the most recent 10-year period, the trend in numbers appears to be unchanged or up slightly. However, the number recorded on both flyways (approximately 290,000) is still well below the North American Waterfowl Management Plan's (NAWMP) target of 385,000 birds by the year 2001.

The NAWMP is dedicated to the recovery of waterfowl populations to the mid 1970s levels, and to the conservation of the wetland ecosystems required to support these levels. The plan was signed in 1986 and is an international agreement between Canada, the United States, and Mexico. By establishing population and habitat goals, it provides a framework for cooperative management of waterfowl between the three countries. The NAWMP operates through a series of joint ventures. The Black Duck Joint Venture (BDJV), signed in 1989, is designed to gather information vital to ensuring sustained populations of black duck and other waterfowl that share their breeding range. The existence of the BDJV is a commitment wildlife agencies place on this species and its management. A strategic plan has been developed to implement breeding ground surveys, pre-season banding, and research programs.

Since its inception, the BDJV has allocated hundreds of thousands of dollars toward its goals. For the 1993-94 fiscal year, $870,000 have been identified by the Canadian and American governments (not including the salaries of provincial and federal agency staff). This dollar figure reflects the amount spent each year since 1989.

Prior to the BDJV, concern in the numbers of black duck recorded during the MWS prompted the Canadian Wildlife Service to begin systematic breeding pair surveys in the Atlantic provinces, Quebec, and Ontario in 1984. With the BDJV, these early surveys were modified and expanded in 1990 to provide comparable surveys throughout the main breeding range.

Analysis of survey data from 1990 to 1993 indicates Nova Scotia's black duck population has not changed or has experienced a small decrease. Analysis of a smaller number of areas repeatedly surveyed from 1986 to 1993 indicates the province's population has increased. Results of the international survey from 1990 to 1992 suggest a range-wide decline for black duck breeding pairs continues. Although small increases were recorded in Ontario and New Brunswick, declines were recorded in Maine, Quebec, and Newfoundland. However, a minimum of five years is required by the survey design to reliably confirm a population trend.

The greatest decline in breeding black duck numbers has occurred in its southwestern range (Ontario). In addition to habitat loss, changes in land-use patterns are believed to favour breeding mallard over black duck. In this area, an increase in breeding mallard populations corresponded with a decrease in breeding black ducks.

In addition to harvest restrictions, recovery of waterfowl populations depends upon restoring wetland ecosystems and maintaining their ecological values. Under the NAWMP, Nova Scotia is part of the Eastern Habitat Joint Venture (EHJV) {Volume 15, No. 3 NS Conservation}. Established to work on habitat issues, the EHJV has produced some notable accomplishments since its inception. For example, the Province has stewardship agreements with three forestry companies. Wetlands on 775 170 hectares (1.91 million acres) of private land and 580 940 hectares (1.43 million acres) of provincial crown lands leased to these companies are under these agreements. In 1993, the value of the EHJV program in Nova Scotia was in excess of one million dollars.

A significant step for wetlands conservation in any jurisdiction is the adoption of a wetlands policy. Nova Scotia is in the process of developing such a policy that will embrace the goals set forth in province's Sustainable Development Strategy, and be in support of global tenants adopted in the International Convention on Biodiversity.

Management agencies, organizations, and individuals are trying to reverse declines in waterfowl populations throughout North America. A great deal of time, effort, and expense has been directed at identifying population trends and limiting factors affecting the black duck population. Large amounts of money have been contributed by hunters, non-hunters, and interest groups to organizations such as Ducks Unlimited and the Nature Conservancy for wetlands conservation. Waterfowl hunters pay a tax to harvest this resource by having to purchase duck stamps applied to state and federal waterfowl permits. The revenue from this purchase supports wetlands conservation activities through the NAWMP or Wildlife Habitat Canada.

There have been many successes in habitat restoration and conservation, and toward stabilizing the black duck population. However, based on the MWS, the population has not increased and surveys of the breeding population indicate continuing declines in some parts of its range over the last four years. Habitat loss and changes in land-use patterns continue. The review of banding information may reveal that non-hunting mortality factors are affecting survival. If confirmed, these factors need to be identified and managed where possible.

The efforts of many organizations and individuals have ensured that the black duck in Nova Scotia and eastern North America will not become threatened or endangered. It will continue to contribute to the environmental and cultural values of the province in the future.