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Sandra Orsillo

Publications and source records attributed to Sandra Orsillo.

4 recordsLinked to original sources
USGS1995

Breeding bird survey: Population trends 1966-92

The North American Breeding Bird Survey (BBS) was begun in 1966 to collect standardized data on bird populations along more than 3,400 survey routes across the continental United States and southern Canada. The BBS has been used to document distributions and establish continental, regional, and local population trends for more than 250 species. We summarize here survey-wide patterns in the 1966-92 population trend estimates for 245 species of birds observed on a minimum of 40 routes with a mean relative abundance of 1.0 bird per route. Survey-wide trend estimates are also summarized for six groupings of birds, providing insight into broad geographical patterns of population trends of North American birds.

Book chapter↗
USGS1995

Mapping of bird distributions from point count surveys

Maps generated from bird survey data are used for a variety of scientific purposes, but little is known about their bias and precision. We review methods for preparing maps from point count data and appropriate sampling methods for maps based on point counts. Maps based on point counts can be affected by bias associated with incomplete counts, primarily due to changes in proportion counted as a function of observer or habitat differences. Large-scale surveys also generally suffer from regional and temporal variation in sampling intensity. A simulated surface is used to demonstrate sampling principles for maps.

Book chapter↗
USGS1995

Geographic patterns in relative abundances and population trends of breeding and wintering loggerhead shrikes in North America

In North America, the Breeding Bird Survey and the Christmas Bird Count provide data that are collected at sites visited each year, and the site-specific data can be placed in a Geographic Information System and smoothed to produce contour maps of relative abundance and trend for the United States and southern Canada. We develop these contour maps for Loggerhead Shrike (Lanius ludovicianus) data from both surveys, and compare the patterns derived from each survey to evaluate the consistency of trends and relative abundances within physiographic strata. Patterns in relative abundance seem to be associated with strata, especially in the breeding season, but trends are often heterogeneous within strata. Because of limitations of the surveys and observed geographic patterns of shrike trends in the survey data, we suggest that there is no natural scale for the analysis of shrike-habitat associations.

Book chapter↗