Estimating density and effective area surveyed for American woodcock
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Abstract
The American Woodcock (Scolopax minor; hereafter, woodcock) Singing-ground Survey (SGS) is conducted annually during the woodcock breeding season, and survey points along survey routes are set 0.4 mile (0.65 km) apart to avoid counting individual birds from >1 listening location. The effective area surveyed (EAS) at a listening point is not known, and may vary as a function of land-cover type or other factors. To define the relationship describing distance between vocalizing woodcock and an observer and how cover types influence that relationship, we broadcast a recording of woodcock vocalizations in 2 land-cover types (forest and field) at varying distance. We evaluated the proportion of call broadcasts detected as a function of distance and fit regression curves to detection data to estimate a distance (r*) where the area above the curve at distances <r* was equal to the area under the curve at distances >r*, which allowed determination of the radius of an area where detection probability was effectively 1.0. This EAS had a radius (r*) of 198 m for forest, 384 m for field, and 309 m for both of these land-cover types combined, and an estimated size of 12.3 ha for forest, 46.3 ha for field, and 30.0 ha for both land-cover types combined. We used this information to estimate density of displaying male woodcock based on counts from the SGS in east-central Minnesota that incorporated variation in EAS, probability of detection, survey date, and survey route. Our density estimates (5.0 birds/100 ha in 2009 and 7.1 birds/100 ha in 2010) represent the highest density of singing male American woodcock yet reported, and indicated a substantive increase in density between years.
Suggested Citation
Bergh, S.M., Andersen, D., 2019, Estimating density and effective area surveyed for American woodcock, in Proceedings of the eleventh American woodcock symposium, v. 11, Roscommon, MI, Oct 24-27, 2017, p. 193-199, https://doi.org/10.24926/AWS.0125.
Study Area
| Publication type | Conference Paper |
|---|---|
| Publication Subtype | Conference Paper |
| Title | Estimating density and effective area surveyed for American woodcock |
| DOI | 10.24926/AWS.0125 |
| Volume | 11 |
| Year Published | 2019 |
| Language | English |
| Publisher | University of Minnesota Libraries Publishing |
| Contributing office(s) | Coop Res Unit Leetown |
| Description | 7 p. |
| Larger Work Type | Book |
| Larger Work Subtype | Conference publication |
| Larger Work Title | Proceedings of the eleventh American woodcock symposium |
| First page | 193 |
| Last page | 199 |
| Conference Title | Eleventh American Woodcock Symposium |
| Conference Location | Roscommon, MI |
| Conference Date | Oct 24-27, 2017 |
| Country | United States |
| State | Minnesota |
| County | Pine County |