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Long Point Waterfowl and Wetland Research Fund Biologists Take to the Sky to Count Waterfowl by Dr. Scott Petrie & Dr. Shannon Badzinski
Waterfowl biologists have long recognized the importance of using aircraft to aid in population estimation and monitoring of waterfowl. Since the mid 1950s, the United States Fish and Wildlife Service (USFWS), Canadian Wildlife Service (CWS), and several state, provincial, and non-government wildlife agencies have coordinated aerial surveys to estimate annual numbers of breeding pairs of waterfowl during May and June across their principal breeding areas in North America. This “May Breeding Waterfowl and Habitat Survey” is one of the longest running and most extensive wildlife surveys in the world. However, some waterfowl such as Tundra Swans, arctic geese, and numerous sea duck species nest in remote and inaccessible areas of the Arctic where they simply cannot be easily surveyed, even from aircraft. Numbers of these species are obtained from aerial surveys conducted annually at wintering areas during January on the “Midwinter Survey.” Numerous other surveys are flown annually in North America, many of which are conducted at staging areas during spring and fall migration. Recognizing the importance of tracking numbers of migrating and staging waterfowl, CWS began conducting fall and spring aerial surveys in the lower Great Lakes region of Canada in 1968. Because of those early survey efforts, the wetland complex associated with Long Point, ON, was identified as one of the most highly used areas by migratory waterfowl in eastern Canada. In order to monitor long and short-term trends in numbers and determine broad-scale habitat use of waterfowl, CWS continued to conduct periodic surveys of Long Point's wetlands throughout the 1970s and 1980s. In 1991,
CWS empowered the Long Point Waterfowl and Wetlands Research Fund (LPWWRF) with the responsibility of conducting fall and spring aerial surveys of waterfowl at Long Point. Recently, LPWWRF also began coordinating and conducting surveys of waterfowl wintering on the lower Great Lakes. This “Lower Great Lakes Survey” is conducted in mid January each year and is flown along the Canadian and American shorelines of lakes St. Clair, Erie, and Ontario – areas that are traditionally not adequately covered by the “Midwinter Survey.” Many people ask how surveyors can possibly count and identify species while flying 160 kilometres per hour, 100 metres above large mixed flocks of waterfowl. Well, it is not an easy task, but with considerable practice, birds can be relatively easily identified and their numbers quickly and relatively accurately estimated (not counted!). As you can imagine, estimating numbers of waterfowl is not an exact science and each observer has slightly different techniques. Most surveyors simply count small groups of birds, but when flocks get large, counting individuals takes far too much time. In those circumstances, surveyors often subdivide very large flocks into smaller-sized blocks of birds (say 25, 50, 100, 500, 1000, etc.) to estimate their numbers. Estimating numbers of birds, especially in large groups, is complicated by flock configuration and density. To help surveyors increase their estimating skills, several computer programs have been developed that display computer generated random dots and flying ducks, geese, and swans on the screen in various configurations and densities. Photographs of waterfowl flocks of known size also can be used as practice. Practice helps to reduce error, but even very experienced surveyors may overestimate or underestimate numbers of birds. Still, errors made by an observer generally even out over the course of the survey, and the total number is a fairly good index what is actually present. Maintaining the same surveyors for long periods of time is important and also ensures that observed changes in relative numbers of birds are real and not simply due to the estimating abilities of different surveyors.
Scott Petrie estimates and records waterfowl numbers during an aerial survey of Long Point. Un inventaire aérien a permis à Scott Petrie d'estimer le nombre de sauvagine qui effectue un arrêt dans la région de Long Point. Photo: Theodore Smith Estimating the numbers of birds is the first challenge, but surveyors also must estimate numbers of each species of waterfowl present. There are several different ways to do this from the air. First, each duck species has characteristic colour patterns on its wings, which is very useful when birds are flying. However, sometimes birds do not fly or are too distant, or light conditions are such that other clues must be used to distinguish species. When this occurs, the relative bird size, flight characteristics, behavior, and/or general habitat can provide a reliable determination of which species are present. With practice, surveyors can quickly subdivide large mixed flocks into smaller groups, estimate their numbers, and determine the proportion of each species present in the flock. All of this information is quickly recorded into cassette recorders during the flight, and is later transcribed and summarized to provide an estimate of the total number of each species present during the survey. LPWWRF typically flies six surveys during the fall and five during spring. Individual surveys are combined to provide overall estimates of waterfowl numbers and use at Long Point during each season. Because waterfowl surveys have been conducted consistently since the 1970s by CWS and LPWWRF, Long Point is one of the best-surveyed wetland complexes in North America. The long-term data set contains valuable information on species-specific waterfowl population trends, migration chronology, and habitat use. These data have been invaluable in revealing several interesting patterns and trends in waterfowl behavior and habitat use at Long Point. For example, diving duck use of Inner Long Point Bay during fall has declined steadily since the 1970s, but their use of Lake Erie off the south shore of Long Point has increased substantially during that same period. Diving ducks have established a pattern of spending the day on the lake and then flying into the inner bay to feed at night. This habit has become more prevalent over time and likely is a response to increased human disturbance on the inner bay. Another interesting trend revealed by LPWWRF survey data was the substantial increase in numbers of scaup, Common Goldeneye, and Bufflehead following the expansion of zebra mussels into Inner Long Point Bay after 1990. More recently, there has been a substantial decline in the number of diving ducks using Long Point (see graph) during spring and fall, which has been particularly noticeable for scaup and Canvasback. These changes may be the result of a number of factors, including increased human disturbance, continental population declines, and/or redistribution to other staging areas.
Aerial waterfowl survey programs, such as the ones conducted at Long Point, will continue to provide very important information on the numbers, distribution, and habitat use of waterfowl over long periods of time. These long-term data play an integral role for directing research into potential factors that may affect waterfowl populations during breeding, staging, or wintering periods. Ultimately, data generated by aerial surveys provide biologists with the best possible information for monitoring and managing waterfowl populations (and their habitats) throughout North America. Until technology is developed to collect waterfowl abundance and distribution data in a more accurate and efficient way, biologists will continue to take to the sky and fly with the birds to count waterfowl.
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Throughout the history of waterfowl and wildlife management, several techniques have been developed and used to count or track birds to determine population sizes and habitat use. These methods included mark-recapture techniques (e.g., banding, color-marking, and radio and satellite transmitters) and ground-based or aerial surveys. Because waterfowl often congregate in large numbers and are found in wetland habitats, they are generally quite easily observed and counted from the air.
