Ecological Fitting: Use of Floral Nectar in Heliconia stilesii Daniels by Three Species of Hermit Hummingbirds

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Abstract
Three species of hermit hummingbirds-a specialist (Eutoxeres aquila), a generalist (Phaethornis superciliosus), and a thief (Threnetes ruckeri)-visited the nectar-rich flowers of Heliconia stilesii Daniels at a lowland study site on the Osa Peninsula of Costa Rica. Unlike H. pogonantha Cufodontis, a related Caribbean lowlands species wit a less specialized flower, H. stilesii may not realize its full reproductive potential at this site, because it cannot retain the services of alternative pollinators such as Phaethornis. The flowers of H. stilesii appear adapted for pollination by Eutoxeres, but this hummingbird rarely visited them at this site. Lek male Phaethornis visited the flowers frequently in late May and early June, but then abandoned this nectar source in favor of other flowers offering more accessible nectar. The strong curvature of the perianth prevents accessby Phaethornis to the main nectar chambers: instead they obtain only small amounts of nectar that leaks anteriorly into the belly of the flower.