Determining natal origins of birds using stable isotopes (d34S, dD, d15N, d13C): model validation and spatial resolution for mid-continent mallards / Daniel W. Coulton, Robert G. Clark, and Craig E. Hebert.

Includes bibliographical references (pages 19-21).

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 platyrhynchos)
on the basis of feather
δ34S,
δD,
δ15N
and
δ13C 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 prior 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 by 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 Forest.
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