STATE OF THE GREAT LAKES 2005
WHAT IS THE STATE OF GREAT LAKES BIRDS?
Although Great Lakes bird populations appear to be recovering from the effects of contaminants such as DDT,
Great Lakes bird populations are still impacted by habitat loss and degradation.
The Issues
• Wetland loss, water level stabilization, non-native
species introductions, sedimentation, and
contaminant and nutrient inputs have
contributed to the loss and degradation of
important breeding habitats for wetland-
dependent birds in the Great Lakes region.
• Colonial waterbirds from the Great Lakes are in
poorer health than those from clean sites in the
Maritime provinces, as observed by monitoring
populations of several waterbird species, and by
tracking contaminants present in the eggs of
herring gulls.
• Bald eagle populations depend on large areas of
habitat for breeding and hunting. Continued
development along the shorelines of the Great
Lakes will cause further loss and degradation of
important bald eagle habitat. Persistent
contaminants are also a concern for this species,
as bald eagles are relatively rare, so high levels of
contaminants in individuals affect the health of
whole populations.
Caspian tern with two nestlings. Photo: U.S. EPA Great
Lakes National Program Office.
The Indicators
Wetland-dependent bird diversity and abundance
Because many species of birds live and breed on
Great Lakes wetlands, the diversity and abundance of
these birds can indicate the health of our coastal and
inland wetlands. By monitoring these characteristics
of wetland-dependent birds, we can determine trends
in bird populations and the ability of the Great Lakes
wetlands to support these populations. This
information can be used to develop more effective,
long-term conservation strategies.
Contaminants in colonial nesting waterbirds
Another indicator of bird population health is trends
in contaminant concentrations in Great Lakes colonial
waterbirds (gulls, terns, cormorants, and herons). As
colonial waterbirds are among the top aquatic food
web predators in the Great Lakes ecosystem, they
accumulate contaminants to a greater degree than
other organisms that are lower on the food chain. We
are able to compare trends in contaminants, as well as
ecological and physiological trends for colonial
waterbirds across the Great Lakes, because they breed
on all of the Great Lakes.
Productivity of bald eagles
As the top avian predators in the nearshore and
tributary areas of the Great Lakes, bald eagle
populations are responsive to contaminant stresses,
food availability, and the availability of prime habitat
over most portions of the Great Lakes shoreline. Bald
eagle populations serve as an indicator of both bald
eagle habitat quantity and quality.
The Assessment
Many of the declining bird species across the Great
Lakes use wetland habitats almost exclusively for
breeding and foraging. This suggests that their
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STATE OF GREAT LAKES BIRDS
decline may be linked to wetland habitat conditions.
The population trends of some bird species appear to
coincide with fluctuations in Great Lakes water
levels. Bald eagle populations have increased
dramatically since their decline caused by DDT. The
percentage of nests producing one or more healthy
fledglings and the number of young produced per
territory has risen, which indicates that the current
bald eagle population is healthy and capable of
increasing.
The ecological effects of contaminants on bird
populations include eggshell thinning, failed
reproductive success, and population declines.
Although colonial waterbirds appear to have
recovered from these effects, physiological
abnormalities are still present in Great Lakes herring
gulls. Since the monitoring of herring gull eggs began
in 1974, most contaminants in gull eggs have
decreased by at least 50 percent, with some
contaminants decreasing by more than 90 percent.
Polybrominated diphenyl ethers (PBDEs), used as
fire retardants in plastics and common household
items, have increased dramatically in gull eggs in the
last 20 years In bald eagles, concentrations of the
primary organochlorine contaminants (DDE and
PCBs) are decreasing or are stable but are still above
the recommended no observable adverse effect
concentrations.
Current Actions
Health of bald eagle populations continues to be
assessed by the number of territorial pairs, success
rate of nesting attempts, number of fledged young
per territorial pair, and developmental deformities in
the young. In addition, concentrations of persistent
organic pollutants and selected heavy metals are
measured in unhatched eggs, nestling blood, and
feathers.
The Great Lakes Herring Gull Egg Monitoring
Program is the world's longest-running annual
monitoring program for contaminants in wildlife.
The longevity of the egg database makes it possible
to examine changes in contaminant concentrations in
wildlife over time.
Programs to restore many degraded wetland areas
have been initiated through efforts of local citizens,
organizations and government agencies.
Volunteers across the Great Lakes region are using
standardized monitoring protocols to help gather
wetland-dependent bird data.
Actions Needed
High quality wetland habitats and adjacent upland
areas must be maintained to support populations of
Great Lakes birds. Factors that impact wetland health
such as water level stabilization, non-native species
invasions, and inputs of contaminants, nutrients, and
sediments should be addressed.
Monitoring programs must be continued and
maintained through continued volunteer recruitment
efforts and training activities.
Reproductive rate data for the shoreline populations
of Great Lakes bald eagles imply that widespread
effects of persistent organic pollutants have
decreased, however there are still gaps in the pattern
of reproductive recovery that must be explored and
remediated. In addition, information on genetic
structure of these shoreline populations is needed.
Although the effects of persistent organic pollutants
on bird populations appear to have decreased,
investigations of the sources and impacts of emerging
contaminants such as PBDEs are needed.
To Learn More
For further information related to Great Lakes bird
populations, refer to the State of the Great Lakes
2005 report, which, along with other Great Lakes
references, can be accessed at
www.epa.gov/glnpo/solec.
02/06
EPA 905-F-06-907
IISG-05-33
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