U.S. Fish & Wildlife Service

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Division of  Migratory Bird Management

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American Woodcock Singing-ground Survey

LIMITATIONS
The survey, while covering the core of the breeding range for this species does not cover the entire breeding range. Secondly, because no effort is presently made to estimate detection probability for observers conducting the survey, it is not possible to estimate absolute abundance from the counts obtained.  Furthermore, observer data should be used as a covariable in trend estimation to adjust for differences in observers' ability to hear woodcock.

Data contained herein is summarized at the route level only.  We currently lack the ability to provide users with computer programs required to estimate trends from such data.  To estimate state and regional trends, we calculate weighted averages from individual routes for each area of interest.  We weight regional estimates by state and provincial land area.  Current trend estimation procedures require at least 2 non-zero counts by the same observer for a route to be used in analyses.  Extrapolating our estimated trend statistics (% change per year) over time (e.g. 30 years) may exaggerate the total change over time.  More detailed information about survey procedures or analyses of these data can be found in the annual American Woodcock Population Status report in the "Reports" section of the Division of Migratory Bird Management web site. (http://www.fws.gov/migratorybirds/reports/reports.html)

POINT OF CONTACT
Becky Rau
Data Administrator, Branch of Population & Habitat Assessment
Division of Migratory Bird Management, USFWS
11510 American Holly Drive
Laurel, MD 20708
voice mail:  (301) 497-5862
fax:  (301) 497-5871
rebecca_rau@fws.gov

LITERATURE CITED

Duke, G. E. 1966. Reliability of censuses of singing male woodcock. J. Wildl. Manage. 30:697-707.

Goudy, W. H. 1960. Factors affecting woodcock spring population indexes in southern Michigan. M. S. Thesis. Michigan State Univ., E. Lansing. 44pp.

Kelley, J.R., Jr., R.D. Rau.  2005. American woodcock population status, 2005. U.S. Fish and Wildlife Service, Laurel, Maryland. 15pp. For current status information visit http://www.fws.gov/migratorybirds/reports/reports.html

Link, W. A., and J. R. Sauer. 1994. Estimating equations estimates of trends. Bird Populations 2:23-32.

Mendall, H. L., and C. M. Aldous. 1943. The ecology and management of the American woodcock. Maine Coop. Wildl. Res. Unit. Univ. Maine, Orono. 201pp.

Owen, R. B., Jr., J. M. Anderson, J. W. Artmann, E. R. Clark, T. G. Dilworth, L. E. Gregg, F. W. Martin, J. D. Newsom, and S. R. Pursglove, Jr. 1977. American woodcock (Philohela minor = Scolopax minor of Edwards 1974), Pages 149-186 in G. C. Sanderson, ed. Management of migratory shore and upland game birds in North America. Int. Assoc. of Fish and Wildl. Agencies, Washington, D.C.

Sauer, J. R., and J. B. Bortner. 1991. Population trends from the American Woodcock Singing-ground Survey, 1970-88. J. Wildl. Mange. 55:300-312.

Sauer, J. R., and P. H. Geissler. 1990. Estimation of annual indices from roadside surveys. Pages 58-62 in J. R. Sauer and S. Droege, eds. Survey designs and statistical methods for the estimation of avian population trends. U. S. Fish and Wildlife Service, Biol. Rep. 90(1). 166pp.

U.S. Fish and Wildlife Service. 1990. American woodcock management plan. U.S. Fish and Wildlife Service, Washington, D.C. 11pp.

Whitcomb, D. A. 1974. Characteristics of an insular woodcock population. Mich. Dept. Nat Resour., Wildl. Div. Rep. 2720. 78pp.

PURPOSE
The American woodcock (Scolopax minor) is a popular game bird throughout eastern North America. The management objective of the U. S. Fish and Wildlife Service (FWS) is to increase populations of woodcock to levels consistent with the demands of consumptive and non-consumptive users (U. S. Fish and Wildlife Service 1990). Reliable annual population estimates, harvest estimates and information on recruitment and distribution are essential for comprehensive woodcock management. Unfortunately, this information is difficult and often impractical to obtain. The American Woodcock Singing-ground Survey was developed to meet part of these information needs by monitoring changes in annual abundance indices.

PROCEDURES
The Singing-ground Survey was developed to exploit the conspicuous courtship display of the male woodcock. Early studies demonstrated that counts of singing males provide indices to woodcock populations and could be used to monitor annual changes (Mendall and Aldous 1943, Goudy 1960, Duke 1966, and Whitcomb 1974). Beginning in 1968, routes were located along lightly traveled secondary roads in the center of randomly chosen 10-minute blocks within each state and province in the central and northern portions of the woodcock's breeding range. Each route is 3.6 miles (5.4 km) long and consists of 10 listening points. The routes are surveyed shortly after sunset by an observer who drives to each of the 10 stops and records the number of woodcock heard peenting (the vocalization by displaying male woodcock on the ground). Additional data recorded to the stop level includes odometer readings, time, disturbance levels and any other pertinent remarks. Acceptable dates for conducting the survey are assigned by latitude to coincide with peaks in courtship behavior of local woodcock. However, it is necessary to conduct the survey during the designated survey dates in order to avoid counting migrating woodcock. Because adverse weather conditions may affect courtship behavior and/or the ability of observers to hear woodcock, surveys are only conducted when wind, precipitation, and temperature conditions are acceptable.

Each route should be surveyed during the peak time of singing activity. For editing purposes, "acceptable" times are between 22 and 58 minutes after sunset (or, between 15 and 51 minutes after sunset on overcast evenings). Due to observer error, some stops on some routes are surveyed before or after the peak times of singing activity. Earlier analysis revealed that routes with 8 or fewer acceptable stops tended to be biased low. Therefore, only route observations with at least 9 acceptable stops are included in the analysis. Data preceding 1987 does not take this into account. Therefore, the field woodcock heard on acceptable stops (Accpwdck) contains a blank or a zero, which indicates the field was not assessed to begin with. Routes for which data are received after the deadline are not included in the analysis but are included in future trend estimates. Surveyors not following the proper procedures outlined above, affect the number of acceptable stops and woodcock heard on those stops.

The survey consists of about 1,500 routes. In order to avoid expending unnecessary manpower and funds, approximately one half of these routes are surveyed each year. The remaining routes are carried as "constant zeros." Routes for which no woodcock are heard for 2 consecutive years enter this constant zero status and are not run for the next 5 years. If woodcock are heard on a constant zero route when it is next run, the route reverts to normal status and is run again each year. Data from constant zero routes are included in the analysis only for the years they were actually surveyed. Sauer and Bortner (1991) reviewed the implementation and analysis of the Singing-ground Survey in more detail.

Annual indices are calculated for each state and province that participates in the survey as well as for the 2 Woodcock Management Units (Eastern and Central). These indices are derived by finding the deviation between the observed count on each route and that predicted by the long-term (e.g., 1968-2002 trend for 2002 indices) regional or state/provincial trend estimate. These residuals were averaged by year and added to the fitted trend to produce annual indices of abundance for each region, state, and province. Yearly variation in woodcock abundance was superimposed on the long-term fitted trends (Sauer and Geissler 1990). Thus, the indices calculated with this method portray year-to-year variation around the predicted trend line, which can be useful for exploratory data analysis (e.g., observing periods of departure from the long-term trend). However, the indices should be viewed in a descriptive context. They are not used to assess statistical significance and a change in the indices over a subset of years does not necessarily represent a significant change. Observed patterns must be verified using trend estimation methods to examine the period of interest (Sauer and Geissler 1990, Link and Sauer 1994).

Again, more detailed information about survey procedures or analyses of these data can be found in the annual American Woodcock Population Status report in the "Reports" section of the Division of Migratory Bird Management web site. (http://www.fws.gov/migratorybirds/reports/reports.html)

DATABASES
One database based on the American Woodcock Singing-ground Survey is available online through the FWS/USGS Migratory Bird Data Center. This database contains the route-level raw count data collected for individual routes sampled during the survey.

DOWNLOADABLE FIELD DEFINITIONS

Field Name

Field Definition

Year

The year the survey was run

StProvCd

Numeric code given to individual states or provinces State codes

Cntycode

Numeric code assigned to the county the route is in - FIPS codes

Routeno

3 digit numeric code identifying route

Statuscd

Alpha code assigned to route Status codes

RteName

Description of route location

Date

Date survey was run

Obscode*

Observer code that enables users to identify changes in route observers

Sunset

Time of Sunset at beginning of route. Route start time depends on sky condition and sunset time see Sky condition codes

Sky

The sky condition at beginning of survey Sky condition codes

Temp

The temperature at beginning of survey Weather codes

Wind

The wind velocity at beginning of survey Weather codes

Precip

The precipitation at beginning of survey Weather codes

Stop1

The civilian time recorded at stop 1 before listening for woodcock

Stop10

The civilian time recorded at stop 10 before listening for woodcock

Totalhrd

Total woodcock heard on stops 1 - 10

TotalStp

Total number of stops where observer listened for 2 minutes

AccpStop            

Total number of acceptable stops where observer listened for 2 minutes -determined by FWS personnel

Accpwdck            

Total number of acceptable woodcock heard on stops 1 - 10; determined by FWS personnel

*The observer code is the 1st 3 letters of the observer’s last name. “ROU” is short for Route Not Run. “C-Z” is short for Constant Zero. “NEW” is short for New Route.

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