ASSESSING NATAL REGIONS FOR MIGRATORY JUVENILE ACCIPITERS USING HYDROGEN ISOTOPES

Identifying and protecting key natal grounds is crucial for conserving wildlife populations. This is particularly true for migratory species, such as raptors, with large geographic ranges. Most methods for tracking migratory individuals (e.g., banding or telemetry) can only provide information about mobility after the individual is trapped, which makes it difficult to identify natal region. However, isotope values in animal tissues record information about an individual’s history. Hydrogen isotope (δD) values in feathers are routinely used to estimate natal latitude for birds of prey because geospatial gradients in δD values are closely tied to temperature and precipitation. Here we use δD values in feathers to determine the natal regions for 10 juvenile Sharp-shinned hawks (Accipiter striatus) and 12 juvenile Cooper’s hawks (Accipiter cooperii) that were trapped in Idaho between September and November, 2016. We anticipated that hydrogen isotopes would indicate some individuals were relatively local while others traveled south from Canada. Sharp-shinned hawks may breed as far north as Southern Alaska while Cooper’s hawks only breed at lower latitudes. Although neither hawk is considered endangered, determining their natal grounds is beneficial to conservation efforts because they are good environmental barometers. We discuss our results and their conservation implications. Deforestation is an ongoing problem that is detrimental to many species, including raptors. Increasing anthropogenic activity across large swaths of the northeastern USA and western Canada may have serious ramifications for forest-dependent accipiters that breed in these regions.