Why do seagulls have dark wings? It may help them glide in the air

Gliding birds tend to have long and thin wings, but seagulls seem to have a trick that lets them soar on short, wider wings

Why do seagulls have dark wings? It may help them glide in the air
Gliding birds tend to have long and thin wings, but seagulls seem to have a trick that lets them soar on short, wider wings