How sunbirds harvest nectar from flowers
Sunbirds are among the most attractive birds around, especially the males. The females on the other hand are rather drab. The food of sunbirds is largely nectar, taken off a wide range of flowers, both native and exotic. In the case of exotic flowers, when the birds are not able to reach the extra long corolla tube, they tend to puncture the base of the corolla to obtain the nectar direct.
Most sunbirds have slender, curved bills whose tongues are long and just as slender, often projecting way out beyond the tip of the bill (see above). But have you ever wonder how these birds harvest the nectar from the flowers?
Well, the tongue of most sunbirds is a closed tube along the major part of its length. This tube is formed by the inward rolling of the edges to meet at the top, thus effectively giving the bird a straw with which to suck up the nectar. The tip of the tongue is usually split and bi-tubular.
Thus when the bird pokes its bill into the corolla tube of the flower and extends its tongue, the straw-like tip will automatically take up some of the nectar through capillary action.
Input and images of male Olive-backed Sunbird (Nectarinia jugularis) (top) and male Crimson Sunbird (Aethopyga siparaja) (bottom) by YC.