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Bromeliads in bloom: Pollination
Many species of bromeliads are pollinated by hummingbirds. To make sure the birds
find them in the dense, tangled foliage of the jungle canopy, bromeliads have to
make themselves visible for the tiny birds. Brightly colored flowers usually aren’t
enough, as they’re too small. Instead, some bromeliads have tinged certain leaves
with bright reddish, contrasting colors. This advertisement for pollinators is
called phyllo-flagging. The signals can be on bracts in the inflorescences or on
tips of the leaf rosettes, which direct the birds to the hidden flowers in the
bromeliad tank.
Bromeliad inflorescences typically have many individual flowers, but only a
few open each day. In this way, a single plant can bloom for several weeks. This
provides the hummingbirds with a reliable source of nectar, causing them to make
regular stops at a given plant. Biologists call this behaviour trap-lining. In turn,
the regular visit of the hummingbirds guarantees a reliable pollination of the
bromeliad’s flowers.
Though nectar-sipping, pollinating birds are quite small – the smallest hummingbird
weighs just one gram! Nevertheless they’re considerably larger than most insects.
Thus, flowers that seek to attract birds produce large quantities of liquid nectar,
which hummingbirds extract with their brush-like tongues.
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Bromeliads in bloom: Pollination (MP3, 651 KB)
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