Why does bird flight look so effortless over the ocean?Bird flight is one of the most interesting aspects of birds at sea. Many species of seabird may need to fly hundreds of kilometres to find food, or migrate around the world to get to their breeding grounds. Some of these birds may not see land for days. Thus, most species have evolved similar morphology to deal with such long flights. Most importantly, the body of a bird is generally lightweight. They have relatively light bones that are “pneumatisized”, that is, they are full of large air spaces. In some species, the total weight of their feathers is heavier than the total weight of their bones. And of course, birds are well known not to have teeth.
Southern sea birds show some interesting adpations to bird flight. In general, wings that are long and pointed are best for this type of flight. Both the secondary feathers, and the middle (or forearm) of the wing where they are located, assist in providing lift, and are thus better developed than the primary feathers on the distal bones of the wing (which are more to do with manoeuvrability). The strong winds of the southern seas keep aloft the biggest wingspans of the world, with the Royal and Wandering Albatross stretching over 3 metres from wing tip to wing tip.
There is also an important concept in birds and flight, called ‘wingloading’. This is expressed as a ratio between the length of the wings and the weight of the bird;
the lighter the body to the longer the length, the more energy efficient the flight. Birds at the surface of the sea, such as albatross, have the best wing loading ratios of all animals.
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