Nest markers are used commonly to identify and mark locations of nests
. However, they also may attract predators and increase nest predation
. We tested the effect of plastic flagging on predation of artificial
duck nests, during two consecutive 14-d period, along two 45-km segmen
ts of graveled road near Crandall, Manitoba, Canada. Estimates of dail
y mortality rates between flagged and unflagged nests did not differ,
but the power of rejecting the null hypothesis was low. Daily mortalit
y rates of nests were higher between day 0 and 8 than between day 8 an
d 14. A flag-by-interval interaction was significant, indicating that
flagged nests had a higher mortality rate than unflagged nests between
day 8 and 14. Differential nest-site vulnerability may affect predati
on soon after nest construction, whereas flagging may increasingly inf
luence predation as nests age. We recommend that nests not be market w
ith flagging and that natural objects be used to aid in nest relocatio
n.