MN
Restore the Call: Minnesota Status Report
for the Common Loon
Known as the Land of 10,000
Lakes, Minnesota boasts 11,842
lakes that are larger than 10 acres
in size. There are more loons in
Minnesota—an estimated 4,600
territorial pairs or 52% of the
breeding population—than in all
U.S. states (except Alaska).
Although the state’s loon
population is healthy, current
environmental threats require
monitoring and action.
The loon is a key biosentinel of aquatic integrity for lakes and near
shore marine ecosystems across North America. Supported by a grant
from the Ricketts Conservation Foundation, which first proposed
the idea, Biodiversity Research Institute has initiated the largest
conservation study for the Common Loon. The goal is to strengthen
breeding populations in their existing range and to restore loons to
their former breeding range. This work will advance our understanding
of loon ecology and allow us to apply that knowledge to help restore the
integrity of ecosystems where loons once thrived. State working groups
and associated conservation plans will be developed in partnership with
the Minnesota Department of Natural Resources.
A Series Publication by BRI’s Center for Loon Conservation
in Partnership with the Ricketts Conservation Foundation
September 2013
Status of Breeding Loon Population in Minnesota
Distribution
Historically, Common Loons (Gavia immer) bred
throughout the state, as far south as Iowa and the
prairie region, although they were likely uncommon in
the prairies. By 1900, loons were nesting in what is now
central Minneapolis. Today, breeding loons range across
the northern two-thirds of the state (Figure 1).
Minnesota Loon Monitoring Program
In 1994, the Minnesota Department of Natural
Resources (DNR) implemented a Loon Monitoring
Program. With the assistance of volunteers, the DNR
annually gathers information on Common Loons on
more than 600 lakes, distributed among six regions,
or index areas, that include: Kandiyohi, Otter Tail,
Becker, Aitkin/Crow Wing, Itasca, and Cook/Lake
Counties (Figure 1). These regions represent different
stressors that may affect loons and their habitats such
as densities of roads, human population, and acid rain
sensitivity (Hanson 1996).
Results from the monitoring program indicate that
Minnesota’s loon population has been stable over the
last two decades. Although the average number of chick
and juvenile loons reported per pair of adults is highly
variable from year to year, their numbers have also
remained stable across all index areas.
Male and female loons equally share incubation duties, which
last 27-30 days. Both pair members also share in attending to
the needs of their young.
Movements
Loons migrate from Minnesota in late fall (Kenow et
al. 2002). They are often observed on Lake Michigan,
where they stop over before migrating south. Adults
leave before juveniles, so young loons arrive on the
wintering grounds without prior knowledge or
experience.
Band recoveries indicate that loons in Minnesota
spend the winter in either the Gulf of Mexico or the
Atlantic Ocean (Figure 2). In the Gulf of Mexico they
range as far west as Corpus Christi, Texas east to
Tampa Bay, Florida. In the Atlantic, loons winter off
the shore of North Carolina. Recent satellite tracking
showed one adult spent the winter at an inland
reservoir in Tennessee (Kenow et al. 2002).
Figure 1. Breeding range of Minnesota Common Loons and six
index areas used for long-term monitoring.
2 Conservation Concerns
Threats to Minnesota’s loon populations
include: loss of breeding habitat; direct human
disturbance to shoreline nests and chicks; water
level fluctuations (especially related to changing
climate); contaminants (e.g., lead and mercury;)
and hazards on the wintering grounds (e.g.,
marine oil spills and fishing nets). Loons are
long-lived; they have relatively low fecundity
and a poor ability to colonize new areas. A
recent loon survey in 2013 found a few loon
pairs in the southern counties, an encouraging
sign that the lake habitat in those areas may
still be suitable for them.
Recreational pressures may affect breeding loons.
Evidence of the loon’s ability to acclimate, however,
suggests that properly designed mitigation efforts
and, more importantly, outreach initiatives can be
successful in many instances.
Figure 2. Breeding and wintering range for the Common Loon. Movements
of loons are based on recoveries and observation of individuals banded by
Biodiversity Research Institute (BRI). The winter range densities are from
the National Audubon Society’s Christmas Bird Count, 2002-2012. Data
from birds/party hour are log transformed.
“A thing is right when it tends to preserve
the integrity, stability, and beauty of the biotic
community. It is wrong when it tends otherwise.”
—Aldo Leopold
American author, scientist, ecologist,
forester, and environmentalist
Chicks are able to fend for themselves and attain
flight at 11-12 weeks. Note the light grey bill and
buffy-edged back feathers, which are characteristics
of young of the year.
3
The Success of Loons in Voyageurs National Park
Loons of Voyageurs
May 25, 2005
A loon study conducted from 1983 to 1986 in VNP documented
the loss of loon nests from flooding and found that the overall
number of chicks hatched per number of territorial adult pairs
was extremely low, especially on Namakan Lake (Reiser 1988). As a
result, in 2000 the International Joint Commission (IJC) issued an
order, named the 2000 rule curve, to revise water level regulations
in the Park. This order minimized water level fluctuations, thereby
reducing the number of flooded and stranded loon nests.
May 31, 2005
Voyaguers National Park (VNP) is dominated by four major
waterbodies: Rainy, Namakan, Sand Point, and Kabetogama
Lakes. Water levels in these large lakes have been controlled by a
hydroelectric dam at the outlet of Rainy Lake and by other dams
on Namakan Lake since the early 1900s. It is well documented that
water level fluctuations impact loon nesting success (DeSorbo et al.
2007).
The average number of loon chicks hatched on Namakan Lake
under the 2000 rule curve was three times as high as the average
number of chicks hatched under the previous water management
scheme in 1970. In 2006, a record number of 37 loon chicks was
observed on Namakan Lake (Windels et al. 2013). There was little to
no change in the average number of loon chicks observed on Rainy
Lake between 1970 and 2000. This result was most likely because
Rainy Lake, more than 10 times larger than Namakan, experiences
less water fluctuation. VNP is a good example of how proper
wildlife management and policies can aid and benefit loons and
other shoreline nesting wildlife.
Loons build their nests close to the water’s edge
leaving them vulnerable to water level fluctuations
that can flood or strand nests. These photos
depict a loon’s nest that was flooded due to
rapidly rising water levels.
35
Avg. number of chicks per year
30
25
20
15
25
10
5
0
The number of chicks has increased since the implementation of water level
regulations.
4 7.8
1980s
2000s
Figure 1. Loon chick production on Namakan
Lake in Voyageurs National Park before and after
the implementation of the 2000 rule curve.
A Case Study
Common Loon Demographics
Much is known about the demographics of the Common
Loon based on a 28-year monitoring program of
color-marked individuals from across North America
(n>5,000) and associated movement studies using
satellite telemetry (n>50 individuals) by Biodiversity
Research Institute (BRI).
For example, on average, individual loons produce 5-10
fledged young over a lifetime. This is based on a model
using known national rates for fecundity of 0.24 fledged
young per female (or 0.48 fledged young per territorial
pair), average first year breeding at 6 years of age, 3
year old survivorship of 48 percent, 3-20 year annual
survivorship of 92 percent, and 20-30 year annual
survivorship of 85 percent).
Models developed by Biodiversity Research Institute in
conjunction with the U.S. Environmental Protection Agency
and U.S. Fish and Wildlife Service indicate that a long-term
average of 0.48 fledged young per territorial pair is needed
for a sustainable loon population (Evers 2007).
Typically, about 18-20 percent of the summer adult
population represents individuals that may be oversummering, but not attempting to breed (i.e., 3-5
year olds).
Common Loons are poor colonizers; adults disperse an
average of one to two miles from their previous breeding
territory and fledged young disperse an average of 12
miles, although the record is just over 100 miles. (Evers
et al 2010).
The Common Loon,
prominent and charismatic,
is highly valued by the general public.
Color banding provides information on interseasonal movements, between-year territory fidelity, mate switching, estimated
minimum survival, individual behavior, loon social dynamics (Evers 2007), and links local breeding populations to key winter
habitat. Many of these findings can then be related to productivity. To date, BRI researchers have banded more than 5,000 loons.
5
The Importance of Suitable Lake Habitat for Loons
Protection of loon breeding habitat is
critical to maintaining the integrity
of loon populations and avoiding
further degradation of suitable
habitat. Because of the loon’s top
trophic-level position, high visibility
to people, limited dispersal ability,
and relatively slow replacement
rate, the loon is widely used as an
indicator species for tracking aquatic
integrity (Evers 2006).
Water Quality Affects Loons
Loons breed in a wide variety
of freshwater aquatic habitats.
However, they prefer lakes larger
than 60 acres with clear water, an
abundance of small fish, numerous
small islands, and an irregular
shoreline that creates coves.
Lake size and configuration are
important determinants for loon
density, as well as undisturbed
shoreline. Water quality is an
important habitat feature for
breeding loon success; loons
are visual predators, therefore
clear water is crucial for foraging
efficiency.
Eliminating or reducing pollution
discharge into a lake from urban
storm water pipes, farm field runoff,
and forestry practices will protect
or restore lake water quality. If
excessive amounts of nutrients,
particularly phosphorus, enter a
lake, then algae populations can
increase and reduce water clarity.
Submerged and emergent lake
vegetation also plays a critical
role in protecting water clarity.
Lakes or reservoirs with abundant
vegetation often have higher water
clarity and greater fish diversity
and abundance (Valley et al. 2004).
Aquatic plants stabilize the lake
bottom, compete with algae for
nutrients (keeping algal populations
in check), and provide important
6 Top: Loons (and people) depend on clear water, a healthy lake plant, and fish
community, and natural shorelines. Bottom left: High densities of carp root in the
lake sediment, which can lead to increased turbidity (right).
habitat. Lake vegetation also attracts
an abundance of invertebrates that
provide prey for many fish species
(Keast 1984); these fish then provide
a food source for loons.
Carp and bullhead may dominate
lakes with no submerged
vegetation. Carp forage on lake
bottoms, stirring up nutrient-laden
sediment. The resulting murky
water blocks sunlight to aquatic
plants that stabilize the lake
bottom causing these plants to die.
Water Quality Protection
and Restoration
The Minnesota Department of
Natural Resources has worked to
improve lake health and integrity
statewide. State agencies, local
governments, and citizens are
actively monitoring, assessing,
and implementing watershed
protection and restoration
projects to reduce lake and river
pollution.
Actions Needed to Strengthen and Maintain Sustainable Loon
Populations
Evidence of the loon’s ability to acclimate suggests
that properly designed conservation efforts can be
beneficial in many instances (Evers 2007). Over the
years, BRI’s research has found the following actions
to be successful or have potential for success:
Monitoring Loons
Continue and expand the Minnesota Loon Monitoring
Program into the south central region of the state.
Use standardized survey methods to collect data on the
number of territorial pairs, nesting pairs, location of
nests, chicks hatched, and those surviving >6 weeks of
age. A critical component of monitoring is to determine
the cause of nest failure or chick loss.
Lake Restoration and Rehabilitation
Assess the potential impact aquatic invasive plants,
such as milfoil, may have on fish diversity and
abundance, and ultimately on loons.
Maintain Healthy Fisheries
Rafts have been proven to be an effective management tool
in Common Loon reproductive studies on New England lakes
and ponds. With rafts, hatching success increased by 51%
on lakes with stable water levels and 119% on those with
fluctuating systems (DeSorbo et al. 2007).
Assess potential adverse impacts from changing fish
composition. For example, carp, an invasive species
more common in the southern part of the state,
impacts water clarity and disrupts the local fish
community.
movements for adults and juveniles (using colormarked individuals and transmitters), assessing
effectiveness of signs and rafts, identifying impacts
from predators and invasive species, and investigating
risks from contaminants in breeding, staging and
wintering areas.
Research
Outreach
Develop new research projects as needed and maintain
current projects that best guide conservation and
management. Such projects include determining
survival rates, tracking intra- and inter-seasonal
At visitor centers in public parks, create greater
awareness of the presence and requirements of loons
through the use of dioramas, exhibits, communication
pieces, and video and slide presentations.
The generous
assistance of
hundreds of
volunteers allows
the Minnesota
Department of
Natural Resources
to monitor loons
each year on more
than 600 lakes.
7
Literature Cited
DeSorbo, C.R., K.M. Taylor, D.E. Kramar, J. Fair, J.H. Cooley,
D.C. Evers, W. Hanson, H.S. Vogel and J.L. Atwood. 2007.
Quantifying and characterizing the reproductive advantages
gained by raft-nesting Common Loons (Gavia immer) on
artificial impoundments and natural lakes in Maine and New
Hampshire. J. Wildl. Manage. 71:1206-1213.
Evers, D. C. 2006. Loons as indicators of aquatic integrity.
Environ Bioindicators 1:18-21.
Evers, D. C. 2007. Status assessment and conservation plan
for the Common Loon (Gavia immer) in North America. U. S.
Department of Interior, Fish and Wildlife Service, Biological
Technical Publication. Washington, D. C.
Evers, D.C., J. D. Paruk, J. W. McIntyre and J. F. Barr. 2010.
Common Loon (Gavia immer). Account 313 in A. Poole, editor.
The Birds of North America. Cornell Lab of Ornithology,
Ithaca, New York.
Hanson, E. W. 1996. Monitoring the Common Loon
population in Minnesota: Assessment of the 1994 and 1995
survey results, the accuracy of volunteers and aerial surveys,
and the power of detecting trends. M.S. Thesis, Univ. of
Minnesota, Minnesota.
Keast, A. 1984. The introduced aquatic macrophyte,
Myriophyllum spicatum, as habitat for fish and their invertebrate
prey. Canadian Journal of Zoology 62: 1289-1303.
Kenow, K. P., M. W. Meyer, D. C. Evers, D. C. Douglass and J.
Hines. 2002. Use of satellite telemetry to identify Common
Loon migration routes, staging areas and wintering range.
Waterbirds 25(4): 449-458.
Reiser, M. H. 1988. Effects of regulated lake levels on the
reproductive success, distribution and abundance of the
aquatic bird community in Voyageurs National Park,
Minnesota. National Park Service Resource Management
Report MWR-13, Omaha, Nebraska.
Valley, R. D., T. K. Cross and P. Radomski. 2004. The role of
submerged aquatic vegetation as habitat for fish in Minnesota
Lakes, including the implications of non-native plant
invasions and their management. Minnesota Department of
Natural Resources, Special Publication 160.
Windels, S.K., E. A. Beever, J. D. Paruk, A. R. Brinkman, J.
E. Fox, C. C. MacNulty, D. C. Evers, L. S. Siegel, and D. C.
Osborne. 2013. Effects of Water-Level Management on
Nesting Success of Common Loons. Journal of Wildlife
Management (in press).
Suggested Citation for this Report
Paruk, J.D., D.C. Evers, and K. Taylor. 2013. Restore the
Call: Minnesota Status Report for the Common Loon.
Biodiversity Research Institute. Gorham, Maine. Science
Communications Series BRI 2013-25. 8 pages.
Project Funding
Funding for this project has been generously provided by the
Ricketts Conservation Foundation, which was formed to support
the conservation of wildlife and natural resources.
BRI’s mission is to assess
emerging threats to wildlife
and ecosystems through
collaborative research and to
use scientific findings to advance
environmental awareness and
inform decision makers.
Acknowledgments
BRI wishes to acknowledge Rich Baker and Krista Larson, of MN DNR,
and Eric Hanson for the initial design and implementation of the MLMP.
Credits
Editing/Production: Deborah McKew
Maps: Ian Johnson, Krista Larson, and Andrew Gilbert.
Photography: Cover: Landscape by yinyang-iStock; Loon portrait by
Daniel Poleschook. Page 2: Breeding loon pair by Daniel Poleschook. Page
3: Banded loon; juvenile loon by Daniel Poleschook. Page 4: Nesting loon
nest by Daniel Poleschook; Loon nests courtesy of Voyageurs National Park.
Page 5: Banded loon by Daniel Poleschook. Page 6: Fishing loon by Daniel
Poleschook; Carp by Czanner-iStock; Turbid water by Jim Paruk. Page 7:
Loon on raft by Jonathan Fiely; Volunteer boaters by Daniel Poleschook.
For copies of this report,
please contact:
David Evers, Ph.D.
BRI’s Center for Loon
Conservation
[email protected]
www.briloon.org
19 Flaggy Meadow Road, Gorham, Maine 04038
phone 207-839-7600