Wintering locations of Least Bittern breeding in Canada assessed using stable isotope methods

Understanding the spatial linkages between breeding and non-breeding grounds of migratory species is important for assessing factors influencing population-specific trends and to guide regional conservation actions. In Canada, the Least Bittern (Botaurus exilis) is considered threatened under the Species at Risk Act. Due to the secretive behaviour of this small heron, information regarding migratory pathways and wintering locations is limited. To estimate the geographic locations of potential wintering grounds, we collected body contour feathers from museum specimens of Least Bittern sampled from across their breeding range in Canada. We measured the hydrogen, carbon, and nitrogen isotopic compositions of feathers to estimate the locations of Least Bittern wintering grounds using assignment-to-origin algorithms. The regions of the highest likelihood of origin of sampled Least Bittern were wintering sites in Mexico, central America along the Gulf Coast, and possibly coastal and Amazonian South America. Habitat loss is acknowledged as the main contributor to the population decline of Least Bittern, and these results may help understand potential factors driving their populations and support conservation and management efforts across their wintering range.