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Abstract
The difficulty of making valid comparisons between historical and contemporary data
is an obstacle to documenting range change in relation to environmental modifications.
Recent statistical advances use occupancy modeling to estimate simultaneously the
probability of detection and the probability of occupancy, and enable unbiased comparisons
between historical and modern data; however, they require repeated surveys at the
same locations within a time period. We present two models for explicitly comparing
occupancy between historical and modern eras, and discuss methods to measure range
change. We suggest that keepers of historical data have crucial roles in curating
and aiding accessibility to data, and we recommend that collectors of contemporary
specimen data organize their sampling efforts to include repeated surveys to estimate
detection probabilities.