The Hawaiian Islands are home to a group of birds found nowhere else—
the Hawaiian honeycreepers. This group of about 50 species (many of which are now extinct) appears to have descended from a single species of Asian rosefinch that made it to the islands between 4 and 5 million years ago. The ancestral rosefinch likely had a short, fat bill and fed on seeds—
however, many honeycreeper species have long, curved bills and feed on flower nectar; the bill shape of particular species fits perfectly with the flower shape of the plants they feed on. This fact might lead you to say:
Some species of honeycreepers evolved with long, curved bills because they needed to feed on the nectar of particular flowers.

Questions

1. Is it likely that variation in bill sizes and shapes existed within the population of rosefinches that inhabited the Hawaiian Islands 4–5 million years ago?
2. Is it likely that variation in foraging (that is, how an individual hunts for food) existed within this population of rosefinches?
3. Would all birds in the original population demonstrate these traits?
4. In an environment where few animals feed on a particular flower’s nectar, would an individual with a slightly longer and thinner bill and the behavior of flower foraging have high evolutionary fitness?
5. How do differences among individuals in evolutionary fitness affect the traits of a population?
6. Reflect on your answers to questions 1–5, and explain why the statement bolded above sounds right, but isn’t.