Conducting a Variable Circular Plot Point Count

Byrne, Michael

This Standard Operating Procedure (SOP) explains the implementation of a point-count survey with distance estimation. This survey utilizes an adaptation of variable-circular plot (VCP) technique (Reynolds et al. 1980, Scott et al. 1986, Buckland et al. 1993, Ralph et al. 1993, Fancy 1997, Nelson and Fancy 1999, 2001). It is intended to be implemented at predetermined sampling locations, generated under a spatially-balanced random-sampling design, as a part of the Southeast Coast Network (SECN) landbird monitoring protocol. Bird surveys are limited to the breeding season (April – June) in an attempt to sample species that have the highest likelihood of reproducing within a park. Point counts of birds are conducted with the variable circular plot (VCP) methodology (Reynolds et al. 1980, Scott et al. 1986, Buckland et al. 1993, Ralph et al. 1993, Fancy 1997, Nelson and Fancy 1999, 2001). An important benefit of using the variable circular plot method is the ability to accommodate a wide range of bird species, each of which possesses a different singing style and each of which may occur in a variety of acoustically-different habitats. VCP counts operate by essentially allowing the habitat to determine the size of the area being surveyed. Surveys occur from 0530 – 1100 from the center point of the 0.5-ha macroplot used as part of SECN sampling design. Station locations are determined as part of the spatially-balanced random sampling design utilized by this protocol and several other terrestrial vital signs (e.g., vegetation communities, amphibian communities, fire fuels). At each station, counts are separated into four time segments of equal duration, 0-3 minutes, 3-6 minutes, 5-9 minutes, and 9-12 minutes. Distance to each bird detected will be estimated into one of four distance classes (0-25 m, 25-50 m, 50-100 m, >100 m). All detections, auditory or visual, resident or migrant, breeder or non-breeder, regardless of distance detected from the observer, are counted and recorded. Each station is sampled two times during the breeding season, at least three weeks apart, in an effort to capture migrants that arrive at different times of the year, and improve detectability of all extant birds.

Conducting a Variable Circular Plot Point Count

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