What are the threats to loons today?
A. Human activities are causing loons to disappear from many lakes.
Traditional nesting areas have been destroyed by development of shorelines
and islands for summer homes, campgrounds, and marinas. Being disturbed
by tourists, pets, motorboats, jet skis, etc., especially during sensitive
nesting and chick-rearing periods, can reduce or wipe out loon populations.
Pollution of lakes where loons nest can lead to build-up of toxins in
eggs and young. Water pollution can also harm food supplies for chicks
and adults--pesticide run-off, mercury, and lead are some of the worst.
And even today people find dead loons with pellets or bullets in their
bodies. One researcher found that 32% of loon cadavers he autopsied had
If a loon were trying to elude a motorboat, would it be more likely to
dive or to sink into the water? How about if it were trying to elude a
distant Bald Eagle?
A. When a loon wants to get away in a hurry, to avoid a motorboat
or other fast danger, it dives fast! To avoid a distant Bald Eagle, and
to escape detection in the first place while the eagle is still far away,
the loon will slowly sink into the water, without leaving a ripple.
How does mercury from the atmosphere end up in a loon?
A. Most, if not all, of the mercury entering Earth's surface waters
comes from the atmosphere. It gets into rivers, lakes and streams when
it rains. Once in the water, it gets in the food chain.
Q. What kinds and sizes of fish are worst for mercury
A. Large fish like walleye concentrate the mercury because they are
high on the food chain. The larger amount of mercury in larger fish comes
from the many minnows they've eaten, all of which have also taken in mercury.
Q. What are some effects of mercury poisoning on
A. Adult loons can pass mercury on to the egg, and the chick will
have higher mercury levels. The effect is not eggshell thinning, as with
DDT, but is lack of motor coordination in chicks because the mercury affects
their nervous system.
Q. How widespread is mercury pollution in North
A. Dave Evers reports: "Substantial mercury pollution of lakes
and streams already exists on our continent. Global mercury levels are
now 3 to 4 times higher than natural background conditions. Recently,
studies have found elevated levels of methylmercury in the body burden
of loons. Although average whole blood mercury concentrations for Minnesota
and Wisconsin loons are not as high as those found in New England and
the Canadian Maritimes, they are double Alaskan samples that represent
background levels. These blood studies show that loons are exposed to
too much mercury."
Q. Does the mercury in lakes ever "go away,"
or must it forever be part of the food chain, ending up in fish and loons?
A. Dave Evers says, "Mercury can settle out into bottom sediments
and become less available to the food chain. In contrast, if lakes become
acidic, mercury that's in the bottom sediments can actually be dissolved
into the water."
Q. What methods are available to remove mercury from
A. There are no current methods used on lakes.
Q. How do scientists study mercury levels in loons?
A. They take samples of the feathers and blood. These samples show
how much mercury is stored in loons' bodies. As more samples are collected,
scientists hope to have a clearer picture of how mercury and the loons'
health are related. Read more
on the Journey North Website.
Q. What can studying a loon's feathers tell about
mercury in its body?
A. Scientists Joe Kaplan and Keren Tischler are working to figure
out when and where mercury (Hg) gets into the loons' blood. Because feathers
are grown at a known time of year, they are like a snapshot in time. "Using
feather mercury values from hatch year loons found in the winter, we can
hopefully extrapolate what the blood mercury level was at the time the
bird fledged. Mercury tested in these feathers indicates the levels the
young loon had on its natal lake in the north. Then, with a new blood
sample, we can determine changes in the amount of mercury found in blood
since the bird has been on the ocean. An additional bonus is that many
of the young loons have already begun replacing feathers, so we can compare
old and new feathers and determine the changes in mercury over the last
4-5 months. We will do the same thing with 2 to 3-year-old loons that
have spent at least a year on the ocean. Eventually Joe and Kerin would
like to develop an exposure model of mercury that can account for year-round
accumulation of mercury from both the summer and winter territories.
Q. Does intake of mercury cause loons to live
A. There have been cases of loon die-offs with mercury poisoning suspected
as the cause, but the worst problem from mercury is reducing loon reproduction.
Dave Evers repies: "Loons have reproductive FAILURE if they eat fish
with higher than .4 parts per million. Reproduction is impaired when the
fish have .3 parts per million. (Reproductive failure means the young
do not survive.)"
Q. Are food eaten in the summer more likely to give
loons mercury than fish they eat on the wintering grounds?
A. Dave Evers says, "We believe that fish eaten in the summer
are the problem. Here's why: Feathers can be tested for mercury, and feathers
that have grown during the wintertime (on the wintering grounds, before
migration) do not seem to contain high mercury levels."
Q. Why is research on mercury contamination of
loons important for human health?
A. Since loons are so high up in the food chain they may also be a
very good indicator of how mercury could affect humans. Since it's estimated
that 95% of human mercury exposure is from eating fish, these long-them
studies are important to humans. In fact, human consumption of fish is
not recommended on many lakes due to mercury pollution. In the state of
Minnesota for example, 1/3 of the state's 10,000 lakes have mercury advisories,
cautioning people too not eat too many fish from those lakes.
Q. What factors make loons good "early
warning" indicators for human health?
A. Common Loons are ideal indicators for human health because we can
study individual birds over the long-term. This is because loons (1) can
be easily captured and recaptured, (2) are easy to monitor throughout
the day, (3) show fidelity to a breeding territory, (4) are long-lived
and (5) are highly sensitive to the bioaccumulation of methylmercury.
What does the term bioaccumulate mean?
A. It refers to a substance building up, or accumulating, in living
Could someone have a pet loon?
A. Absolutely not! It is against laws in the U.S. and Canada to have
loons for pets. Dave Evers points out that there have been a few people
who have kept loons in captivity, sometimes before they were protected,
and a few with research permits. Mostly loons are "taken care of"
at animal rehabilitation centers if they have been injured or are sick.
These birds are treated and the goal is to release them to the wild again.
The Minnesota Zoo has had the most intensive loon rearing program. They
raised several loon chicks but were not able to keep the young birds alive
to adulthood. Loons do not appear to do well in captivity. There are also
a few stories of people who have "tamed " loons on their lake.
This is an unusual situation and in the few instances it has occurred
the loons were not tame enough to be touched.