Details: Trend Maps 1966-2003
In this analysis, the trend at any point was estimated as a weighted average of trend information from nearby survey routes containing information from the species. Trend on these routes was estimated as a yearly change, using the Link and Sauer (1994) estimating equation procedure. The weights in the average are the standard route-regression weights (Geissler and Sauer 1990, Link and Sauer 1994), and an inverse distance from the point, the allow for decreased influence as distance from the point of interest increased.
Detailed metadata on analysis methods are available from the geographic information portion of the website.