WING DESIGN AND MIGRATORY FLIGHT

ABSTRACT

Since birds are adapted to occupy different niches and have different migrating strategies, they use different flight modes associated with particular wing designs. Long-distance migrants should have narrow wings, that is, a high aspect ratio (wingspan²/wing area) for flight endurance, short wings for time minimization, and a high wing loading (weight/wing area) for fast flight. For energy-minimization, long-distance migrants should have long wings and a low wing loading. Fast-flying species should have pointed wing tips to reduce profile power and streamlined bodies to reduce parasite power, whereas rounded wing tips enhance soaring and gliding performance in slow fliers. Mean aspect ratio for 28 long-distance migrating birds is 8.2, whereas short-distance migrants have a lower aspect ratio (mean 7.4, n = 50). The variation in relative wing loading (body mass^2/3/wing area) is rather high in both groups, but, in general, relative wing loading is lower in long-distance migrants (mean 5.5) than in short-distance migrants (mean 7.3). The flight of short-distance migrants is predicted to be more expensive on average than that in long-distance migrants, which may need more stopovers to feed during their migration flights than species with higher aspect ratios. Mean aspect ratio and relative wing loading for 51 sedentary birds are 5.5 and 6.1, respectively, indicating expensive flight.