When it comes to pollinators, plants are not usually picky. But one tropical plant seems able to choose its suitors, a new study found.

When Heliconia tortuosa resisted researchers’ attempts to pollinate it by hand, they tried introducing the plant to six species of hummingbirds and a butterfly. Only two types of the hummingbirds — those with the longest bills and that travel most extensively — were consistently successful in getting pollen from the plant.

Writing in Proceedings of the National Academy of Sciences, researchers at Oregon State University and the Smithsonian suggest this coyness may be a way for the plants to ensure genetic diversity.