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Facts about Loons

Ecology

Q. What do scientists hope to learn by banding loons?

A.
Scientists are able to identify individual birds and collect information on many topics. They collect data on mercury in loons' bodies, behavior, mating, return rates of loons to lakes, and other natural history information.

Q. How do researches get tags on the loons to track them?

A.
Dave Evers explains: In order to band loons, you must of course be able to capture and handle the birds. The method that researchers are using now is to go out at night with a small boat and outboard motor. The boat holds three people to run a large light, a tape recorder, and a big fish net. In the spring when the loons have chicks you can lure the adult birds near the boat by playing a loon call. When the loons come to investigate the "strange bird" on their lake you shine the light in their eyes and slowly motor up to the bird. Then you dip the net under the bird and pick it up into the boat. We then take the loon back to shore and put metal Fish and Wildlife Service bands on their led (with an identification number) using a pliers. We also put colored leg bands on the bird so we can see them from a distance and identify which bird it is without having to capture them again. For example we might mark a bird with a red band over blue band on the left leg. This marking method has been very successful and safe for the loons as well.


Q. What do loons eat in their summer breeding grounds?

A.
Year round, loons are opportunistic foragers, feeding on fish, aquatic vertebrates and invertebrates, and once in a while plants. During the summer, the loon's favorite food is yellow perch, but they will eat whatever is available and what they can catch. This includes trout (though trout tend to be too fast for loons) and aquatic insects like dragonfly larvae.

Q. What do loons eat in their winter feeding grounds?

A.
During the winter loons eat, among other things, flounder, crabs, lobster, shrimp, gulf menhaden, bay anchovies, and silversides. Menhaden may be so important that it can influence loon migration.

Q. Why do migrating loons frequently fly with their mouth open?

A.
This may allow them a greater flow of air than flying with their mouths closed. Loons frequently make their tremolo call in flight, and they always open their mouths to make this call.

Q. How far (long) can loons fly at one period of time?

A.
Dave Evers says: To my knowledge, there is no definitive information on how far loons fly without stopping. They have been clocked at up to 90 miles per hour and we know that they migrate considerable distances (such as Wisconsin to Florida) but they do stop en route to feed and rest.


Q. How do loons manage to time their arrival on a lake for the very day of, or the day after, ice out?

A.
Here's a good guess: The Great Lakes open up before smaller northern lakes. Many loons fly across Pennsylvania and New York to reach the Great Lakes. Then they make exploratory flights each morning, moving closer and closer to their nesting destination, and flying back if they don't find open water. Sometimes a loon begins checking its lake several days before the lake opens up. That means that the loon will certainly be there the day the ice finally goes out.


Q. What if loons head north too early?

A.
In most years loons arrive back before ice-off and have to wait for a small section of their lake territory to open before they can land. Keep in mind that loons need a running start to take flight so they have to be careful. If a lake were to re-freeze they could get trapped. It seems the loon has adapted its behavior for this special circumstance because we have not seen this in the spring.

Q. What do loons do in most years when they find their lakes frozen?

A.
Remember they can't stand on land! They fly to large rivers larger or bodies of water like the Great Lakes. Then they wait for the small lakes to open to begin the nesting season. They keep checking the situation at their home lakes by taking day trips back and forth.

Q. Why do loons migrate to the ocean instead of spending the winter on inland lakes that don't freeze?

A.
Loons leave their breeding lakes because they freeze up. They don't go farther south, where lakes don't freeze, because a new set of dangers awaits: preying alligators, water that is too warm for loons, or too shallow and murky for diving and hunting. Loons need VERY clear, deep, open water for diving and catching fish. The ocean is the right place for loons in winter.


Q Why would it be a problem for a loon to be on a lake when ice starts forming?

A.
These heavy birds with large feet must run across the water for about a quarter of a mile before taking flight. Like jets, loons need long runways to gather speed before lifting off. If there's ice on the lake, they can't run for lift-off, and they may become trapped on the lake. Trapped loons are at risk of death.

Q. Where do loons stop to rest during their migration?

A.
As they fly from the oceans to their nesting grounds on inland lakes, stopover points are critical to loons. Because the Great Lakes are ice-free in early spring, these sites are some of the first places loons appear in the spring.

Q. How do loons, who breed in fresh water lakes, adapt to salt water when they migrate to the oceans for wintering?

A.
Loons have a special adaptation to handle salty fish and salty water. They have salt glands in their skull between their eyes. These drip almost constantly during the winter season. Dr. Judith McIntyre, an authority on the Common Loon, found that "even young chicks, no more than two weeks old, are competent to remove salt if they are fed saline (salty) solutions."

Q. Why do loons molt?

A.
Feathers get worn out, frayed and weakened. Body plumage must be strong and tight to keep the loon warm and dry in very cold water, and flight feathers must be strong to withstand hard flapping over a long migration twice a year.

Q. When do loons molt?

A.
On the breeding grounds in late summer, a loon molts out of its beautiful breeding plumage. It grows plain brownish gray feathers on its back, top of neck, and head over a white belly and throat. Loons molt again in late winter before they leave their wintering grounds, changing from the brown winter plumage to the full breeding plumage. During this molt, all the flight feathers are lost at one time, making the loon temporarily unable to fly. These new flight feathers will carry the loon to the ocean, and back again in the fall. If one of the flight feathers gets broken, the loon will be stuck with it until next winter. But if it is pulled out at the base, the loon will grow a new one even when it isn't normal molting time.

Q. Why do loons lose and then grow all their flight feathers at once, instead of one or two at a time like crows, hawks, and eagles do?

A.
Loons are completely flightless without every single one of their feathers. But wait-there's more. Loons have relatively heavy bodies and small wings-both adaptations for diving deep into water. With a complete set of flight feathers, their wings have just about the minimum amount of surface area to hold up their bodies. If a loon were to try to fly while missing three wing feathers, the surface area of its wing would be too small to hold up its body! To minimize the time that they are flightless, loons molt all the feathers at once.

Q. How does molting affect a loon?

A.
It takes a lot of energy and body resources to grow feathers. Loons grow a lot of large, stiff feathers all at once. There are 11 primary feathers and 22-23 secondary feathers on each wing. That's a lot of feathers, and they're big! Loons are flightless for about 2-3 weeks while their new feathers develop. This is the time when loons are in greatest danger. Not only are they unable to fly, but they must expend a lot of energy to grow feathers. Since they are using their energy stores they are less able to deal with diseases at this time. They can become severely stressed if they are already weakened from some disease, for example. Or, if they have toxic chemicals stored in their body fat, these toxins can suddenly flood a loon's system when the fat is used for feather growth. Sometimes the loons even may die. A few times, there has been a large loon die-off in the ocean. When this tragic event happens, it's usually February, right when loons are molting and most vulnerable. When the molt is finished, they have brand new feathers for their trip north.

Q. What is the reason for loons 'rafting' in the fall before their southern migration? (Rafting means gathering in huge numbers.)

A.
Rafting may help loons to feed more efficiently. Adults gather on a few large, non-breeding lakes, allowing the young to remain on their breeding lakes without competition as their flight feathers grow all the way in and their wings grow strong enough to finally migrate. Also, as loons lose their territorial drive in late summer and feed in groups, they no longer spend time and energy chasing off other loons. Sharing a space makes more sense because then everyone can spend their time eating. It may also help to prevent loons being attacked by predators because there are more eyes looking out for attacks.

Q. Will loons use any lake for rafting, or are there special requirements?

A.
Lakes where loons form rafts are probably not being used as a nesting territory by a pair of loons, or if it was a nesting territory, the nesting is done and the pair are no longer defending it. The primary importance for a "rafting lake" is that it has to have a lot of fish to feed on. Having islands and deep water seem to be some other important characteristics, as loons tend to raft over the drop-offs in a lake, and the islands provide important protection from wind.

 

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