It’s a bird that isn’t great at flying and is awkward at walking on land, but it’s very skilled at diving. The common loon (Gavia immer), also known as the great northern diver, is an aquatic bird that somewhat resembles a large duck or small goose. Since flying isn’t their strong point, why do loons migrate?
Most birds have hollow bones to reduce their weight for flying. The fact that a loon’s bones are not hollow adds weight to facilitate diving but makes flying more of a challenge. Loons can dive as deep as 200 feet (60 meters) and stay underwater for three minutes. Because of their dense bones, they sit lower in the water than ducks or geese when they swim. The loons’ legs, located near the rear of their bodies, facilitate quick diving but make walking more difficult.
Loons are well-designed for catching fish and well-suited for life in the ocean, where they spend their flightless winters. When spring comes, the loons molt, shedding their gray feathers and growing black ones. They gain stiff wing feathers and begin exercising to build strength for the migration journey. After a couple of months of preparation, they are ready to fly hundreds of miles north to freshwater lakes, where they spend the summer.
Why should loons leave the oceans where they have an abundant food supply? Just think that they wouldn’t have to go through the changes necessary to fly to the northern lakes. They could also avoid the dangers involved in making the migration. They wouldn’t need the complex navigation methods they use to return to the same lakes where they originated. Why do loons migrate? Why not do what many northerners do when they retire and just enjoy life along the warm and sunny ocean shores?
The answer seems to be more beneficial to other living creatures than to the loons. Their departure from the ocean relieves pressure on fish populations in coastal marine areas. More than that, it helps to control fish populations in northern freshwater lakes. Loons return to the north to benefit the northern ecosystems. These birds are well-designed to fill a niche in the ecosystem that other life forms can’t fully meet.
So even though loons are not the best at flying and even less adapted for walking, they have what is needed to fill a niche in the ecosystem. Why do loons migrate? The loon’s migration may benefit other living creatures more than itself. How could natural selection explain this? According to the survival of the fittest, shouldn’t these birds survive and thrive doing their own thing rather than benefiting others? We don’t think natural selection fully explains the design of loons and their lifestyle. We suggest that the common loon is a testimony to the Creator’s wisdom of design in the life system we see all around us.
— Roland Earnst © 2022