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Research
Black Ducks Down Home on Dairy Farms
by Charles Maisonneuve, Société de la faune
et des parcs du Québec, Luc Bélanger, Canadian Wildlife
Service, and Jason Beaulieu, Ducks Unlimited Canada
Aerial surveys in southern Quebec lowlands during spring 1998-1999 have
revealed surprising results. The highest densities of American black ducks,
generally associated with forests, were obtained in agricultural landscapes
dominated by dairy farms. These surveys were carried out under the Eastern
Lowlands Initiative, in partnership with Ducks Unlimited Canada, the Canadian
Wildlife Service, the Institute for Wetland and Waterfowl Research, and
the Société de la faune et des parcs du Québec.
Regions targeted were agricultural lowlands of the St. Lawrence Valley
and Lake Saint-Jean, and agricultural sectors of Abitibi-Témiscamingue
in northwestern Quebec. The objectives were to estimate waterfowl populations,
determine distribution, and build a predictive model of the relationship
between breeding pair densities and multiple habitat variables obtained
through satellite imagery analysis. This will help predict breeding pair
densities in areas not covered by surveys carried out under the Black
Duck Joint Venture and produce a waterfowl habitat map for southern Quebec
lowlands. The map will become a tool for identifying Eastern Habitat Joint
Venture priority areas and for planning and evaluation.
The highest breeding pair densities (178/100 square kilometers) were
recorded in Abitibi-Témiscamingue, and the lowest (74/100 square
kilometers) in the western part of the St. Lawrence Valley. American black
duck and mallard were the dominant species, with more than 70% of the
estimated 38,000 indicated pairs breeding. Within the St. Lawrence Valley,
five main landscapescash crop, dairy farm, heterogeneous agriculture
(mix of the two previous), agro-forested landscape, and forested landscapewere
delimited based on land-use types with the use of LANDSAT-TM satellite
images. Mallards were evenly distributed within these landscapes, but
black duck densities in the dairy farm and forested landscapes were over
three times those obtained in areas of extensive agriculture. In fact,
these landscapes harbour the highest densities of breeding black duck
in Quebec. Some forested habitats used by black ducks, like woodlots and
fencerows, are still covering adequate areas of the dairy farm landscapes,
which is not the case in the cash crop and heterogeneous landscapes.
Habitat modifications in southern Quebec may have had a marked influence
on black duck population declines at the regional and continental scale.
If studied lowlands in Quebec support only 10% of the continental black
duck population, this is probably the segment of the population most at
risk. Modifying agricultural practices and creating cultivars that grow
in harsher conditions may represent a threat for black duck populations
still nesting in dairy farm landscapes.
Thus, the black duck could eventually become an excellent indicator species
in evaluating the environmental quality of agricultural landscapes, both
from water quality and biodiversity standpoints. The species could also
be an indicator of wetland availability and riparian strip, fencerow,
and woodlot conditions. Continuation of the analyses will lead to a model
and map showing black duck habitat potential.
For more information, contact Charles Maisonneuve, Société
de la faune et des parcs du Québec, 675 Boulevard René-Lévesque
Est, 11ième etage, Québec, Québec G1R 5V7, (418) 521-3940
extension 4457, charles.maisonneuve@fapaq.gouv.qc.ca.
Native Warm-season Grass Habitat in One Season
by Thomas G. Barnes, University of Kentucky
Native warm-season grasses (NWSG) provide excellent nesting and winter
cover for a variety of grassland birds, but, until recently, this vegetation
type was difficult to establish, taking 3 to 5 years. It was hypothesized
that before above-ground productivity was seen these grasses spent years
establishing productive root systems that allowed them to compete with
existing vegetation. The proposition became: If competing vegetation is
removed will NWSG seedlings grow above and below ground at the same rate?
Over the past 5 years, University of Kentucky scientists have developed
standard methodologies for establishing NWSG using imazapic, the primary
active molecule in a variety of relatively new herbicides, including Plateau®
and Oasis®. Biologically, imazapic stops photosynthesis by inhibiting
the biosynthesis of branched-chain amino acids through the inhibition
of acetohydroxyacid synthase. Use of imazapic results in little residue,
and thus, effects on the environment and wildlife are minimized. In studies
where the imazapic was fed to mammals and birds, no toxicity resulted.
Its mobility in earth is limited because it binds to soil particles. In
addition, at maximum label-rate application, approximately one-tenth of
imazapic is present when compared to maximum label rates of products using
glyphosate.
Field trials show that tall fescue is effectively eliminated with imazapic
using a full label rate (12 ounces per acre) with one quart of surfactant
and one quart liquid 28-0-0 nitrogen fertilizer. There is enough residual
herbicide activity to provide full weed control for 45 to 60 days, a critical
factor in successfully establishing NWSG. Protocol calls for idle grassland
fields to be burned in March, followed by herbicide application in mid
April, when tall fescue is 6 to 8 inches tall. Native warm-season grass
seed is planted with a no-till NWSG drill in mid May. Through 2000, this
process has resulted in the successful establishment of NWSG in a single
growing season, with flowering and seed production.
Conservation Reserve Set Aside acres are restricted to the use of 4 ounces
of imazapic per acre. A change in protocol will result in a stand of NWSG
that is comparable to using the 12 ounce rate in no-till situations: Follow
burning with the application of glyphosate at the maximum label rate,
then apply 4 ounces of imazapic at the time of NWSG seeding.
With conventional tillage and a good seed-bed, a 4-ounce application
of imazapic at the time of NWSG seeding will provide adequate weed control
for the entire growing season in mid to northern latitudes.
For exotic cool season grass invasion into NWSG stands or for prairie
restoration, it was found that prescribed burning followed by an application
of 10 ounces of imazapic with a non-ionic surfactant provided excellent
tall fescue control and bolstered growth of NWSG and numerous forbs.
There is a downside to imazapic use. Few forbs or wildflowers can tolerate
the herbicide, and some prairie grasses like the wild ryes, switchgrass,
and eastern gamagrass may not be tolerant. Nonetheless, imazapic herbicides
have revolutionized the establishment of native warm-season grasses.
For more information, contact Thomas G. Barnes, Associate Extension
Professor and
Extension Wildlife Specialist, Department of Forestry, University of Kentucky,
Lexington, Kentucky 40546-0073, (859) 257-8633, tbarnes@ca.uky.edu.
Diving Ducks Trends in Chesapeake Bay
by Matthew Perry, Peter Osenton, and Edward Lohnes, U.S.
Geological Survey
Based on aerial surveys during the past 50 years, diving ducks wintering
in Chesapeake Bay have accounted for 23% of Atlantic Flyway and 9% of
North American populations. Continental and local factors have affected
population changes. Factors such as human population increases, water
quality, and food availability have been implicated in the changes in
distribution, abundance, and food habits of some species of diving ducks.
Mid-winter aerial surveys, conducted by U.S. Fish and Wildlife Service
and state wildlife agencies, determine the distribution of and estimate
the size of the bay's waterfowl populations. The bay has annually wintered
approximately 1 million waterfowl on average during the past 50 years.
Diving ducks have declined significantly during this period; the bay now
winters approximately 200,000 diving ducks. Survey results show a decline
in pochards (canvasback, redheads, and scaup), ruddy duck, and goldeneye.
Although there have been major changes during some periods, the long-term
trends of long-tailed duck (oldsquaw) and scoters show that numbers in
the 1990s are similar to those of the 1950s, but bufflehead and mergansers
have shown population increases.
Scientists have determined present food habits by analyses of the gullets
and gizzards removed from ducks obtained from hunters or law enforcement
officers. They separated organisms by species and measured dry weights
and volumes for each sample. They also determined frequencies of occurrence,
average weight, and average volume of the food items for each duck species.
For comparison purposes, they reexamined historic food habits data for
the bay's sea ducks.
Some species of diving ducks have shown major long-term changes in the
food eaten, whereas other species show no change in diet. The percentage
of invertebrates in the diet of most pochards and ruddy ducks has increased
as submerged aquatic vegetation (SAV) has declined. The Baltic clam constitutes
over 90% of the food of canvasbacks. Both species of scaup feed on hooked
mussels, but also rely on clams and barnacles. The redhead did not alter
food preference for SAV, and populations of this species have declined
from over 100,000 to less than 1,000 in the bay.
Baltic clam and hooked mussels are important foods of goldeneye. Bufflehead
also feed on the Baltic clam, but they feed heavily on the dwarf surf
clam, too. The sea ducks rely heavily on mollusks, especially the hooked
mussel and several species of clams. Long-tailed duck appears to select
the gem clam at rates higher than other divers, but food habits of this
species show a diverse diet of other mollusks and crustaceans.
While some species of diving ducks have modified feeding habits to accommodate
changes, other species show little changes in food habits. Species, like
the pochards, that feed in shallow water are probably more affected by
environmental changes in the bay than those that feed in deeper water.
Contributing human factors affecting diving duck populations include
development in the bay's tributaries, increased year-round boat traffic,
and increased levels of contamination of the bay's waters.
For more information, contact Matthew Perry, U.S. Geological Survey,
Patuxent Wildlife Research Center, 11410 American Holly Drive, Laurel,
Maryland 20708, (301) 497-5622, matt_perry@usgs.gov.
Getting to Know Oaxaca's Coastal Island Seabirds
by Juan Meraz, Universidad del Mar
The coast of Oaxaca is characterized by rocky beaches interspersed along
extensive sandy portions of coastline. Just off the coast is a series
of small islands, keys, and rocky formations concentrated throughout Bahías
de Huatulco. Highly mobile organisms, such as birds, occur along the coastal
mainland as well as on adjacent islands. In theory, if there is a large
number of species migrating between the two, the islands should maintain
a high level of diversity. An assumption could also be made that there
should be a great degree of resemblance between species that inhabit both
areas.
The Resources Institute at the Universidad del Mar in Oaxaca initiated
a project to study seabird communities on four small islands near the
coast: Montosa, Cacaluta, San Agustín, and Roca Blanca. Interestingly,
concentrations of brown booby were found on Isla Roca Blanca in the surroundings
of Zipolite beach, which is within the tropical zone where reproductive
conditions for this species are not usually appropriate. It also was surprising
to find many wintering migrant groups of brown pelican and magnificent
frigatebird throughout most of this zone.
On islands closer to sandy portions of the coastline, elegant tern was
found, together with snowy egret and laughing gull. Of particular interest
were osprey and American kestrel, located in the prominent portions of
the islands. Less frequently seen species included spotted sandpiper,
great blue heron, American oystercatcher, red-billed tropicbird, and belted
kingfisher. Numerous groups of storm-petrels and shearwaters were registered
in the open sea. Although these birds were closer to the islands, none
were spotted on them.
At this time, studies have been developed mainly for species identification
and census. In the future, researchers hope to conduct annual inventories
as well as comparisons between species diversity and abundance on the
islands and mainland coast. The importance of studying these areas is
based on two points: studies on Oaxaca's seabirds are limited and tourism
activities are increasing. The modification of the coastline by hotel
construction and the growing number of tourist vessels will make the islands
increasingly important refuges for seabirds. The future well-being of
Oaxaca's seabirds is tied to the protection of these islands.
To date, there has been little or no interest in the islands as tourist
destinations; for this reason, they are still well-conserved areas. Research
projects that gain knowledge about the bird populations there and their
insular habitats will provide the basis for sound conservation strategies
now and in the future.
For more information, contact Juan Meraz, Instituto de Recursos, Universidad
del Mar,
Carr. A Zipolite, km 1.5 Puerto, Angel, Oaxaca, México, C.P. 70902,
(529) 584-3047 or 3049, revista@angel.umar.mx.
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