Why don't you come in and check out my place?

This good-looking guy is the purple-throated carib, Eulampis jugularis, a small hummingbird native to a number of Caribbean islands. He's certainly attractive, but he's not banking on that to bring in the lovely ladies. Turns out that flashy plumage is all well and good, but it's his stash that counts. Two researchers, the Smithsonian's John Kress and Amherst's Ethan Temeles, have discovered that male caribs ensure their reproductive success by protecting territories containing many times the nectar supply that they can use - part of it reserved exclusively for the female guests that they hope to entice.

Caribs are sexually dimorphic. Although coloration patterns are somewhat similar between the sexes, males are considerably larger than females and have a greater wingspan. The females, on the other hand, have a much longer, downturned beak. This means that the females can draw nectar from flowers that are not available to males. This phenomenon, known as sexual resource partioning, leads to malesw feeding from one type of Heliconia flower and females feeding from another. And the females choose males on the basis of the nectar that his territory can provide her. This means the males are highly motivated, in an evolutionary sense, to protect a quality territory.

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