Determining Natal Origins of Birds using Stable Isotopes (delta S-34, delta D, delta N-15, delta C-13) Model Validation and Spatial Resolution for Mid-continent Mallards

摘要

The use of tissue stable isotope values to track animal movements is well-established but independent tests of existing models and assignment accuracy at coarse spatial scales and for non model species are rare Assignment error associated with an existing model for distinguishing origins of North American Mallards (Anas platyrhyn chos) on the basis of feather delta S-34 delta D delta N-15 and delta C-13 values was evaluated Prior information about regional movements reported in Mallard mark recapture studies was accounted for and new models generated and applied to independent data obtained from flightless juvenile Mallard and Lesser Scaup (Aythya affinis) Assignment error of an existing model was reduced from 14 to 8% by incorporating pilot information about mallard movement rates between Pacific and Mid-continent Flyways (range 0 to <1%) in Flyway specific models The revised Mid-continent model correctly assigned 86% of 70 flightless hatch year Mallards captured at breeding areas in central North America during 2005 to origin Assignment accuracy ranged from 76 to 91% over five 1 latitude Increments where Boreal Forest and Prairie regions were increasingly separated from a focal Aspen Parkland region here separating Boreal Forest and Prairie regions from the Aspen Parkland b) 4 latitude provided the highest relative assignment success rates among all three regions Estimated origins of known source scaup were accurate (14 of 16) for birds with feathers grown in Aspen Parkland but not (0 of 5) for those grown in the Canadian North western Boreal For est The results support the use of multiple feather isotopes for assigning natal origins of birds at broad geographic scales but evaluation of factors affecting species specific Isotope differences is required for application of existing models to other species Received 18 April 2009 accepted 9 December 2009