Social and habitat correlates of immigrant recruitment of yearling female mallards to breeding locations / Daniel W. Coulton, Robert G. Clark, Leonard I. Wassenaar, David W. Howerter, and Michael G. Anderson.

Includes bibliographical references (pages 790-791).

Conspecific avoidance and attraction hypotheses
have been proposed to explain patterns of animal
spacing behavior and have been frequently used to explain
habitat selection by dispersers. In birds, tests of these
hypotheses have been limited to fine spatial scales and have
not considered dispersal distance. We used discriminant
function analysis (DF) of feather d34S, dD, d15N and d13C
values to identify yearling female Mallards (Anas platyrhynchos)
that dispersed long distances ([400 km relative
latitude) from natal areas to settle at 22 breeding locations
in the Canadian parklands, 1993–2000; these sites varied in
social (breeding pair density) and breeding habitat (wetland
density and percent nest cover) conditions. DF indicated
that the proportion of yearling female recruits estimated to
be long-distance immigrants in these breeding populations
averaged 12% across sites (range 0–38%). Yearling
immigration rates were positively correlated with conspecific
breeding pair density and negatively correlated with
percent wetland habitat. Settling patterns by yearling
immigrants were most consistent with the prediction of
social attraction, but effects were statistically weak possibly
because inter-regional movements were less variable
annually due to relatively stable wetland conditions in the
southern prairies during the period of study. Our results
suggest immigrants arriving from distant natal sites used
conspecific abundance as a positive cue of habitat quality
when choosing the new breeding sites. Fitness consequences
of these choices should be evaluated.