PUBLISHED: DECEMBER 2005

Glossary

Canonical correspondence analysis (CCA)
A standard method for multivariate direct gradient analysis (regression), whereby multiple species abundance data are related to linear combinations of measured environmental variables (ter Braak, 1986). This method assumes that species abundances vary along environmental gradients in unimodal ways.
Centroid
The center of gravity for a homogeneous area.
In this methodology, only birds observed within 50 meters of a point-count circle's center are used to estimate relative abundances.
Maximum abundance
The maximum species abundance observed over all the years of a study (e.g., 1997 or 1998 for this study), recorded for each point-count station.
Mensurative
Point-count stations
A stop location along a bird survey transect where an observer records all birds heard or seen within a given radius of the stop for a set period of time (e.g., three to five minutes).
Randomization test
A test that uses randomly generated numbers for statistical inference (see http://ordination.okstate.edu/permute.htm).
Redundancy analysis (RDA)
Another standard method for direct gradient analysis done in multivariate space. Multiple species abundance distributions are assumed to have linear relationships to environmental gradients (i.e., linear species response curves).
Regression analysis
Any statistical method in which the mean of one or more random variables is predicted conditioned on other (measured) random variables (see http://en.wikipedia.org/wiki/Regression_analysis).
Shuffling
A method of randomly rearranging data. Data can be shuffled in various ways for randomization tests (e.g., across all point-count stations surveyed or shuffled among point-count stations within transects, but not between them).
Transect
A line used in ecological surveys to provide a means of measuring and representing graphically the distribution of organisms (Oxford Dictionary of Ecology).
Trend surface analysis
An analysis technique designed to separate observed data into large-scale (spatial or regional) components and residual components.
Unimodal
Pertaining to a distribution of data with only one mode, or peak, such as a standard bell curve.
Universal transverse mercator
A map developed by the National Imagery and Mapping Agency (NIMA) using a noncurved rectangular grid system. In this grid, the world is divided into 60 north–south zones, each covering a strip 6° wide in longitude (see http://www.uwgb.edu/dutchs/FieldMethods/UTMSystem.htm).
Year effects
Significant year-to-year differences (in terms of species richness and abundance) in the community observed.