|
Breeding Scaup May Suffer Food Shortages
courtesy of Ducks Unlimited
 Al Afton is a waterfowl researcher who in past years studied bluebills
in Minnesota while working for the Department of Natural Resources. Now
at Louisiana State University, Afton is dedicated to discovering why the
number of bluebills counted in May on their breeding grounds has
declined by about 150,000 per year over the past two decades.
Afton and his student, Mike Anteau, collected lesser scaup from
locations in Louisiana, Illinois, Minnesota, and Manitoba during the
spring of 2000 and 2001. Data from Louisiana suggest bluebills wintering
there are actually in better condition than they were two decades ago,
and research shows bluebills on the Mississippi River near Keokuk, Iowa,
are healthy. However, scaup collected in northwest Minnesota and
northern Manitoba showed physiological declines.
As many as one quarter of North American bluebills migrate through
Minnesota in spring, spending three or more weeks there. It is a crucial
stage in which bluebill feed heavily to store lipids, proteins, and
minerals for egg development.
Afton and Anteau are confident that something is affecting bluebills as
they fly north through Minnesota, but exactly what is uncertain. They
suspect that the recent decline in female scaup body condition is due to
reduced food availability at northern stopover sites during spring
migration. Amphipods are the most important food source for scaup in the
upper Midwest, but declines in these foods could be caused by a variety
of reasons.
Recent invasions or introductions of minnows and/or other aquaculture
practices in semi-permanent and permanent wetlands are affecting
amphipods and other important scaup foods. Fish may be consuming large
quantities of amphipods and other scaup foods or causing subtle changes
in the scaup food sources. Afton theorizes that introduced zebra
mussels, which filter a lot of water but retain contaminants, may be
hurting scaup and scaup food sources as well. Parasites may also be
hurting the bluebill population.
Females arriving on breeding grounds in poor condition must spend more
time feeding at breeding areas to accumulate nutrients necessary for
breeding, so they nest later and are less successful in their
reproductive efforts. Normally hen bluebills average nine to 10 eggs per
clutch, but the mineral shortage could reduce egg production. Anteau and
Afton's findings may warrant additional management efforts to provide
improved habitat with abundant and nutritious food for migrating scaup.
Scaup can also lose weight, lipid, and mineral reserves rapidly if food
supplies are short or deficient. Afton believes that, because sufficient
elements are not plentiful enough, some hens may not nest at all.
Duck unlimited is the world's leader in wetland conservation. They
raised over $175,000,000 for wetlands preservation last year. For more
information visit their website:
www.ducks.org
|
