Decoy trap bias and effects of markers on reproduction of northern pintails / Karla L. Guyn and Robert G. Clark.

Includes bibliographical references (pages 511-513).

Decoy traps have been widely used to trap waterfowl, but trap bias has rarely been
examined. Likewise, researchers often radio-mark animals with the implicit assumptions that
(l) radio-marked individuals are representative of the population and (2) transmitters do
not alter behavior or other measures of interest. In this paper, we quantified possible trap
bias, and combined effects of capture and radio-marking, on attributes and reproduction of
female Northern Pintails (Anas acuta). We found no difference in the age distribution or
size of decoy-trapped versus nest-trapped female pin tails. However, radio-marked females
tended to lay fewer eggs than unmarked females. When analyses were restricted to first nests
only, clutch-initiation dates did not differ between radio-marked and unmarked females. The
number of ducklings hatched did not differ between radio-marked and unmarked females.
Although we did not detect age or size differences between birds caught in decoy traps and
those nest-trapped, it is unclear if either group is completely representative ofthe population.
However, pintails were difficult to capture with decoy traps and the method was time and
labor intensive. Our results suggest that the combined effects of trapping and marking may
negatively affect some aspects of reproduction in pintails.