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Open Mic: Duck, Duck, Goose – Counting North American Waterfowl

Wednesday, November 9, 2016 9:22
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At the Mic: Jason A. Crotty

The federal government does many things, some well and some poorly. One of the things it does well is gather, analyze, summarize, and publish mountains of data, including information about the status of bird populations.

For example, each year the U.S. Fish & Wildlife Service (USFWS) issues a report entitled “Waterfowl Population Status” which presents the results of annual population surveys. The survey—one of many produced by USFWS—has been conducted for more than 60 years and it  is likely the most extensive and comprehensive long-term annual wildlife survey in the world. The data is primarily used to inform decisions about hunting regulations but there is information of interest to birders.

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The data—which encompasses all of North America—is derived from aerial surveys and contains contributions from U.S. and Canadian federal, state, provincial, academic, and conservation entities. The report is compiled by a section of USFWS called the “Division of Migratory Bird Management, Population and Habitat Assessment Branch.”

Every spring, air crews consisting of a pilot biologist and an observer, fly fixed-wing aircraft at low altitude (100-200 feet) over transect lines (totalling more than 80,000 miles) through waterfowl habitat areas. They count birds within a certain distance from the aircraft. However, not all birds are seen from above, so similar counts are conducted on the ground. Using the difference in the aerial and ground counts, researchers develop visibility correction factors to apply to the aerial counts.

Estimates of breeding populations are derived by taking the aerial counts, statistically adjusting them based on the correction factors, and applying them to the entire survey area. USFWS has online training tools, which include quizzes that allow you to test your own species identification and counting skills.

The results from 2016 generally paint a positive picture: many waterfowl species are at or above their historic population levels. (The Northern Pintail is a notable exception, as it has been in a significant long-term decline.) Indeed, for several species of geese the problem may be that there are too many rather than not enough, as there are mounting concerns regarding conflicts with agricultural and urban areas, airport safety, and habitat degradation in the Arctic.

The high abundance numbers in 2016 were despite below-average rain, and the resulting early drying of many wetlands in the Canadian and U.S. prairies. Many of these areas were graded as just “fair” for waterfowl production.

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Here are some of the highlights of the report from the “traditional survey area” (see map) which contains much of the most productive duck breeding area in North America. The survey for this area excludes scoters, eiders, long-tailed ducks, mergansers, and wood ducks because the area does not include much of the breeding grounds for these species.

  • In the traditional survey area, the total duck population estimate was 48.4±0.8 million birds. This was similar to the 2015 estimate, and is 38% higher than the long-term average (1955–2015).
  • Estimated Mallard abundance was 11.8 ± 0.4 million, which was similar to 2015 and 51% above the long-term average.
  • Estimated Gadwall abundance was 3.7 ± 0.2 million, which was similar to 2015 and 90% above the long-term average.
  • Estimated American Wigeon abundance was 3.4 ± 0.2 million, which was similar to 2015 and 31% above the long-term average.

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  • Estimated Green-winged Teal abundance was 4.3 ± 0.3 million, which was similar to 2015 and 104% above the long-term average.
  • Estimated Blue-winged Teal abundance was 6.7 ± 0.3 million, which was 22% lower than the 2015 estimate but 34% above the long-term average.
  • Estimated abundance of Northern Shovelers (4.0 ± 0.2 million) was similar to the 2015 estimate but 56% above the long-term average.
  • Northern Pintail abundance (2.6 ± 0.2 million) was similar to the 2015 estimate and 34% below the long-term average.
  • Abundance estimates for Redheads (1.3 ± 0.1 million) and Canvasbacks (0.7 ± 0.07 million) were similar to their 2015 estimates and were 82% and 26% above their long-term averages, respectively.

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  • Estimated abundance of Scaup (5.0±0.3 million) was similar to the 2015 estimate and the long-term average.

In addition to information about ducks, the report provides information about populations of geese and also habitat conditions. The habitat data is primarily the number of ponds and ice and snow melt conditions in the Arctic and subarctic, all of which are directly related to waterfowl production. USFWS sometimes presents the results in video form: the 2015 survey video is on YouTube.

USFWS also issues annual reports on several individual species including American Woodcock, Mourning Dove, Mottled Duck, Band-tailed Pigeon, and Sandhill Crane. Each of the four major flyways (Atlantic, Mississippi, Central, and Pacific) also issues an annual report that includes population information. These reports—and many others—can be found here and here.

The Facebook and Twitter feeds (and mailboxes) of many conservation-minded birders are full of stories about the dire condition of some bird species. Without detracting from the importance of those cases, there are many species that appear to be holding steady or even increasing and it is important to maintain some perspective. Reliable historical data also helps wildlife managers determine which conservation measures are most effective and facilitates informed decisions on how to utilize finite conservation resources.

Thanks to Josh Dooley (USFWS) for helpful information regarding these reports.

Photo Credits:  Tom Koerner/USFWS: Mallard and Mallards at Sunset.

–=====–

Jason A. Crotty is a birder and a lawyer living in Portland, Oregon. He wrote about volunteering in National Wildlife Refuges in the most recent issue of Birder’s Guide, and about the U.S. Endangered Species Act as it applies to birds, with examples drawn from the Red-cockaded Woodpecker, in the August issue of  Birding.

Join the American Birding Association at www.aba.org!

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