Report on the Ninth Annual C&O Canal Mid-Winter Bird Survey (January 20, 2007)

Overview

The C&O Canal is a National Historical Park on the Maryland side of the Potomac River. Built in the nineteenth century, it formerly carried coal, building supplies, and agricultural goods from Cumberland in western Maryland to Washington, D.C. Now, instead of serving as a transportation corridor, it serves as a quiet retreat for humans and provides habitat for wildlife. The park is 184.5 miles long but less than a mile wide. It transects two physiographic regions, from the eastern edge of the Piedmont in Washington to the western edge of the Ridge and Valley province in Allegany County.

DC Audubon's Midwinter Bird Survey aims to census birds along the entire length of the C&O Canal. Annual surveys such as this are important for monitoring the long-term health of our native bird populations. Regular censuses take on added significance in the midst of rapid land-use changes, such as those experienced by the greater Washington area in the last decade.

Methods

The format for the 2007 count was the same as for past surveys. On the morning of January 20, teams of volunteers walked their assigned sectors. Most teams covered 2-5 mile segments; a few hardy individuals covered more. Volunteers counted the number of individuals for each bird species they encountered, and kept separate data for each mile segment. Backtracking allowed some teams to find additional species for their mile segment, but not to add to the numbers of those species already observed. For the first time in the history of the C&O Canal Midwinter Bird Survey, volunteers could enter their data online through the DC Audubon website.

Coverage and Participation

This is DC Audubon's most ambitious activity and requires the assistance of many individuals and organizations. Without their enthusiastic support, the count would not be possible. Since its founding in 1999, the Midwinter Bird Survey has become a welcome activity for regional birders, many of whom have covered the same sections for several years consecutively.

Despite predictions of high winds, almost all volunteers covered their assignments on the count date. Sightings were reported from 171 of the canal's 185 mile segments. Two mile segments were closed because of erosion of the towpath. By the week of the count, we had assigned all 183 possible mile segments, but for one reason or another, data were not reported from 12. It is difficult to predict last-minute events like sudden illness, car trouble, or bad weather in advance. Such vagaries make it difficult to achieve full coverage in any given year. At least 80 volunteers from three states and the District of Columbia joined the count in 2007. (A full list is given below.) After an all-time low in miles covered in 2006, we were pleased to achieve 92% coverage in 2007.

Data Presentation

The full results from the 2007 Midwinter Bird Survey are compiled in the linked spreadsheet. It should open in any spreadsheet program, such as MS Excel, MS Works, OpenOffice Calc, Google Documents, or others. (If you need a different format, email us.) Bird species are marked in the left-hand column, and rows at the top display the mile segments and lead observers for each segment. Columns at the right display the total number of individuals for each species as well as the number of sectors where each was recorded.

For the most part, the data presented in the data sheet are those reported by volunteers. Several unusual reports were deleted for lack of documentation or corrected after consultation with the team leader established that the report was erroneous. If any participant from last year's count finds further errors in the data sheet, please let us know. Likewise, contact us if data from your segment does not appear.

We apologize for the delay in posting the data from the Ninth Annual Count. Difficulties implementing website software and an unexpected move by one compiler pushed back the reporting date considerably. In the future, we hope to have the data edited and posted before summer.

Results

The overall numbers reported were consistent with past years. Volunteers recorded 84 species and 15,641 total individuals. One species was new to the count: four Greater Yellowlegs appeared in Mile 46. Canada Goose continued its reign as most numerous species with 2257 individuals. Dark-eyed Junco was in second place with 1304 individuals, while European Starling took third with 1254. The most populous mile was Mile 1, which featured 579 birds, most of which were European Starlings. (The first few miles, which pass through Georgetown, often feature large flocks of common urban birds.) The most diverse segment was Mile 22, with 30 bird species reported.

The number of Canada Geese recorded during last year's survey was far below the number present for previous surveys. In 2007, the numbers increased but were still lower than usual. Volunteers found 2257 geese for an average of 26.9 per mile covered. While not as low as last year's 1369 total individuals and 18.5 geese per mile, it is the fourth lowest average and second lowest total. We will watch with interest to see if this is a trend or an aberration.

When Canada Geese are removed from the total, overall bird numbers held steady compared with past counts. The average number of individuals per mile surveyed was fourth lowest, but the absolute total was fourth highest since the count began.

Species Comments

Waterbirds. Highlights were a Black-crowned Night-Heron in Mile 1 and a Canvasback in Mile 6. While both species are relatively common in the Washington area, neither is recorded frequently on the canal survey. The 14 Pied-billed Grebes marked an all-time high for that species.

Raptors. Perhaps owing to high winds, most raptors were harder to find than in the past. The one exception was the Bald Eagle, which fell one short of its high count of 23 in 2003.

Gamebirds. Wild Turkeys appeared in good numbers. Once again, Northern Bobwhite was not found on the count. This once-common species has become one of the most rapidly-declining birds in North America.

Gulls. Herring and Great Black-backed Gulls were both below their past averages in 2007.

Kingfishers. For the second year in a row, Belted Kingfishers were present in above-average numbers along the canal.

Woodpeckers. Hairy Woodpeckers had their second-highest year.

Passerines. Over the past three years, Eastern Phoebes continue to fall below their established norms for the canal count. Fish Crows may be underreported. Brown Creepers had their second highest count with 219 birds, as did Carolina Wrens with 542. Kinglets were both below their averages. Eastern Bluebird set a new record with 440, surpassing the 419 from 2000. European Starling had its best year ever with 1254, compared to 1021 in 2004. It was also a good year for Field Sparrows, which set a new record of 41 (previous high: 25 in 2003), Dark-eyed Juncos, which set a record with 1304 (previous high: 1230 in 2003), and American Goldfinches, which set their own record of 291 (previous high: 289 in 2003).

A table comparing the species totals in each year is available at the main canal count page.

List of participants