Blue Tits, Parus caeruleus, as Pollinators of the Crown Imperial, Fritillaria Imperialis, in Britain

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Abstract
It is proposed that the crown imperial (Fritillaria imperialis L.) is a plant pollinated by passerine birds in its native range. The high rate of secretion of sugar (up to 2.1 mg sugar h-1 flower-1), the nectar solute concentration (4-10% w/w), the absence of sucrose from the nectar, and the low amino-acid concentration, point to the passerine bird pollination syndrome. In Britain, this introduced plant is visited by blue tits (Parus caeruleus L.), and bumblebees. The fit of the birds in the flower, and the geometry of the flower, strongly suggests that this plant possesses morphological adaptations to ornithophily. This is confirmed by the fact that flowers visited by blue tits are efficiently pollinated and fertilized, while those visited only by insects, or isolated from visitors, do not produce fruits. This is probably the most northerly case or ornithophily yet reported.