Treesearch

We examine the effect of survey length and radius on the results of point count surveys for grassland birds at Williams Lake, British Columbia. Four- and 8-minute counts detected on average 68 percent and 85 percent of the number of birds detected during 12-minute counts. The most efficient sampling duration was 4 minutes, as long as travel time between points was under 15 minutes. Density estimates derived from 4-minute counts were significantly lower than 12-minute counts for most radius sizes. A larger radius yielded a larger number of detections but not always proportionally with the...

Species richness, composition, and abundance of farmland birds were compared between point counts (50-m, 100-m, and 150-m radius half circles) and territory mapping on three 40-ha plots in Québec, Canada. Point counts of smaller radii tended to have larger density estimates than counts of larger radii. Territory mapping detected 10 species more than 150-m radius point counts. Territory mapping at 150-m radius detected more birds per species than point counts; relative abundances, however, were similar. Bird density is probably optimally estimated with a 100-m radius point count. After four...

This paper discusses methods for estimating population trends of Northern Spotted Owls (Strix occidentalis caurina) based on point counts. Although the monitoring program will have five distinct components, attention here is restricted to one of these: roadside surveys of territorial birds. Analyses of Breeding Bird Survey data and computer simulations were used to develop recommendations for design of the roadside surveys. An approach known as "lattice sampling," in which some stations are visited annually and other stations are visited less often, may offer some advantages over the more...

In 1987, the Canadian Wildlife Service (Ontario Region) initiated a program to inventory and monitor trends in forest birds. The Forest Bird Monitoring Program (FBMP) was designed to describe changes in numbers over time for all forest songbirds, to develop a habitat-specific baseline inventory of forest birds (species composition and relative abundance), and to develop regionally accurate habitat association profiles for all common forest birds. It was intended to build upon and augment the broad regional base of the Breeding Bird Survey (BBS). The program relies on volunteers for annual...

Breeding passerine abundances in Great Basin shrubsteppe and grassland habitats were surveyed in southwestern Idaho by using 73 pairs of 200-m radius circular point counts. Points were placed along roads and paired with points 400 m away from roads but in similar habitat. Grassland species such as Horned Larks (Eremophila alpestris) and Western Meadowlarks (Sturnella neglecta) accounted for 65 percent and 21 percent of the total number of individuals counted in both habitat types. Typical shrubsteppe bird species such as Sage (Amphispiza belli) and Brewer's sparrows (Spizella breweri), and...

Roadside point counts are generally used for large surveys to increase the number of samples. We examined differences in species detected from roadside versus off-road (200-m and 400-m) point counts in the Shenandoah National Park. We also compared the list of species detected in the first 3 minutes to those detected in 10 minutes for potential species biases. Results from 81 paired roadside and off-road counts indicated that roadside counts had higher numbers of several edge species but did not have lower numbers of nonedge forest species. More individuals and species were detected from...

Many factors affect the use of point counts for monitoring bird populations, including sampling strategies, variation in detection rates, and independence of sample points. The most commonly used sampling plans are stratified sampling, cluster sampling, and systematic sampling. Each of these might be most useful for different objectives or field situations. Variation in detection probabilities and lack of independence among sample points can bias estimates and measures of precision. All of these factors should be considered when using point count methods.

We established bird monitoring programs in two regions of Minnesota: the Chippewa National Forest and the Superior National Forest. The experimental design defined forest cover types as strata in which samples of forest stands were randomly selected. Subsamples (3 point counts) were placed in each stand to maximize field effort and to assess within-stand and between-stand variation for a variety of bird parameters. Data gathered in 1991 were used to evaluate several assumptions that were made in the experimental design and showed that variance of most bird parameters among strata were...

The use of population size as a measure of health of a species has been a very common tool of ornithologists for many years (Lack 1954, 1966; Hutchinson 1978). Methods for surveying population size are detailed in Ralph and Scott (1981), the excellent compendium by Cooperrider and others (1986), and the manual by Koskimies and Vaisanen (1991). Many types of counting techniques are available to estimate relative abundance and population trends. Probably the most widely used are modifications of unlimited distance point counts (Blondel and others 1981), conducted at a series of counting...

Effects of count duration, time-of-day, and aural stimuli were studied in a series of unlimited-radius point counts conducted during winter in Quintana Roo, Mexico. The rate at which new species were detected was approximately three times higher during the first 5 minutes of each 15- minute count than in the final 5 minutes. The number of individuals and species detected in 15-minute counts declined by >60 percent over the first 3 hours after sunrise. Use of aural stimuli (playbacks of prerecorded warbler "chip" notes, imitated owl calls, "spishing") offset this temporal reduction in...