Cooperative Breeding and Long-Distance Dispersal: A Test Using Vagrant Records
Figure 2
Map projections and buffer calculations, using the Bushtit (Psaltriparus minimus) range as an example.
(a) North American 1983 is the original datum for the ranges and vagrant points. (b) Each range was reprojected to a customized Albers Equal Area projection for the purpose of calculating the centroid of the range. (c) Each range and set of vagrant points were reprojected to a customized Azimuthal Equidistant projection with the point of tangency at the centroid of the range. In this projection, the distances from the edge of the range to each vagrant point were measured. (d) A buffer at the distance from the edge of the range to the farthest vagrant was drawn around the range. The density of vagrants within the buffer was used to calculate an index to measure vagrant frequency. The base map is provided by the National Geospatial-Intelligence Agency [24].
