North American Breeding Bird Survey (BBS) stop-level uncertainty code

The North American Breeding Bird Survey (BBS) (https://www.pwrc.usgs.gov/bbs/) has counted birds annually for over fifty year. Survey 'routes' each consist of 50 'stops' (counts) placed along a line. Inter-stop distances can vary from route to route and from year to year, and precise locations of each stop are not typically recorded.
This script quantifies uncertainty in BBS stop locations using digitized stop locations from the central United States, calculates the resulting habitat uncertainty for each stop, based on the National Land Cover Database (NLCD; https://www.usgs.gov/centers/eros/science/national-land-cover-database), and incorporates this uncertainty into Bayesian multi-species hierarchical models to predict stop-level BBS bird detections. It can be used to repeat the authors analyses, or to produce additional analyses of BBS data from other regions, for other bird species, or for other covariates.