Patuxent Wildlife Research Center - Bird Population Studies
Results are based on a hierarchical model for population change, as described in Link and Sauer 2002a. We use a hierarchical model to produce annual indices of abundance for a region, then estimate trend as the ratio of the annual indices for the first and last year of the interval of interest. The Markov chain Monte-Carlo method used to fit the model is an interative fitting procedure, which produces a series of replicates from which the estimates and their credible intervals can be derived. This summary program uses these replicates, summarized at the level of stratum within states or Provinces, aggregates them into regional estimates for the selected region, and calculates a trend as a ratio of annual indices corresponding to the first and last years of the selected interval.
Output from the program includes:
Although these data have been processed successfully on a computer system at the United States Geological Survey (USGS), no warranty expressed or implied is made regarding the accuracy or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. This disclaimer applies both to individual use of the data and aggregate use with other data. It is strongly recommended that these data are directly acquired from a USGS server, and not indirectly through other sources which may have changed the data in some way. It is also strongly recommended that careful attention be paid to the contents of the metadata file associated with these data. The USGS shall not be held liable for improper or incorrect use of the data described and/or contained herein.
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