Adaptation

Adaptation

Loons have adapted to their aquatic environment in many different ways. We will look at how they move, adapt to less desirable habitats, and adapt their diets.
Loons are said to be one of the most graceful animals on the planet, in the water that is! Gavia immer are able to move swiftly through the water by diving and swimming. Loons have large feet that are webbed with three toes. Their wings are also large and sleek. The feet are located in the back of the body, making it nearly impossible for a loon to take off from land. Loons require water for take off! The wings are used during diving endeavors as well. They act as steering mechanism for the body while under water and as a flight mechanism while in the air. The beating of the wings while a loon is in flight can propel the bird up to 80 miles per hour! Though one would think the feet are used for steering under water, they simply are used to propel the animal through the aquatic environment. The large feet are the reason for underwater speed and diving distance. The feet allow the loon to push itself into the depths of the lake. Gavia immer can dive up to 200 feet down and can stay under water up to five minutes in length. Have you ever been on a lake in northern Wisconsin or Minnesota and witnessed a loon dive? You will notice that one second you see the loon dive under the water and the next it appears a mile across the lake. Okay, maybe not a second later, but pretty quick! Loons are very graceful and sneaky animals. How do they disappear so quickly? Before a dive, loons release air from their body cavities and tuck their feathers close to their sides. This air reduction allows the loon to slip under the water without being detected. Loons like other birds have a very interesting ventilation system in general. Fresh oxygen is pushed down into posterior air sacs in the back of the loon. When the loon takes another breath the air in the posterior sacs moves into the lungs and then into the anterior air sacs. The fresh oxygen always moves to the posterior sacs first and then pushed to the anterior for exhalation. This is not the only adaptation the loon has made to increase diving proficiency! Loons are aquatic birds and then aerial birds. Unlike other birds, the loon has dense rather than hollow spongy bones. This makes them better adapted for diving rather than flying. They also are able to tolerate low levels of oxygen while diving. According to Loon Magic, loons acquire their oxygen while under water through stored oxyhemoglobin and oxymyoglobin in the blood and muscles. As we can see loons are well adapted for diving and flying!
What kinds of adaptations does the loon make when choosing a habitat? A a cool and crystal clear lake is not always readily available as a home for a loon. Loons live in lakes of small size or large size. Other characteristics of loon habitats are clear water, murky water, fresh water, salt water, no vegetation, vegetation, islands and no islands. The various prey items that reside in these different types of lakes also force adaptations when it come to diet!
Another way Gavia immer has adapted to its environment involves the acquisition of nutrients. On the next page, Nutrition, we will see a detailed explanation of the diet of Gavia immer, but now we will look at what the loon does to compensate for low levels of prey availability. Loons definitely have a fish of choice, but are also very opportunistic and make the best of what is available. Gavia immer love trout, if trout is unavailable they will choose another prey item that is in greater abundance and more easily obtained. These cuisine choices include fish, frogs, salamanders, crayfish and leeches. Gavia immer also choose those prey items if the water is murky and fishing becomes more difficult. As stated previously some loons live on lakes that contain no fish at all. In an environment like this, Gavia immer choose to feast on mollusks, insects, and small invertebrates. Baby loons especially have adapted by having a vegetarian diet and consume green aquatic plants rather than fish.

Now that we have seen what kinds of environments loons have adapted to, let’s look at Nutrition.

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