Breeding expansion of sandhill cranes in Quebec

Abstract

Sandhill cranes (Antigone canadensis) were broadly extirpated from much of their historical range in North America at the beginning of the 20th century. Various conservation-related legislation such as the U.S. Migratory Bird Treaty Act have allowed population recovery. The eastern population has been growing rapidly since the 1980s and is thought to have expanded its geographic range to Quebec, Canada. Understanding the colonization and habitat use by the species in previously unoccupied breeding areas is necessary to develop and apply management measures. Using a dynamic occupancy modelling approach, we investigated the recent colonization and extinction patterns of sandhill cranes in Quebec during a 16-year period. We combined data from three data sets (helicopter surveys, breeding bird atlas surveys, and eBird) to increase the spatial coverage and the number of species occurrence records while accounting for imperfect detection probability. Detection probability was highest for the helicopter survey (0.70), whereas the two other data sets had relatively low detection levels (between 0.10 and 0.26). Based on a simulation study successively excluding one the three data sets, we found that excluding eBird data from the analysis produced more biased estimates than with the exclusion of the Atlas and EWS-CWS data sets. Throughout the study, sandhill cranes seemed to have completed their colonization of western Quebec and only recently started to nest in eastern areas. Initial occupancy increased with wetland cover and colonization probability increased weakly with the cover of agricultural areas, suggesting that in our study area sandhill cranes rely essentially on natural wetlands during the breeding season.