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December 2003

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Hot Pink: African Flamingos on the Move

By Margaret G. Zackowitz
For a flamingo, feeding requires a new perspective: upside down. To consume the spirulina algae that is its main source of nutrition, the bird inverts its head so that the bottom portion of the bill faces up. This big mandible also works as a float to keep the bill from sinking too far below the surface. As the flamingo swings its head from side to side, its large, thick tongue pumps lake water into the scoop-shaped bill, where a filter of hair-like projections extracts algae. Excess water is then sluiced out by the tongue. Large gatherings of flamingos require staggering amounts of spirulina. A flock of 100,000 eats 35 tons (31 metric tons) a day, and flocks of more than a million birds have been counted. But algae blooms are fickle in the Rift Valley lakes; even the most lush spirulina growth can die off almost overnight. When conditions change, noisy pink clouds scud toward the next lake. There's no predicting the schedule: Lesser flamingos don't migrate—they wander.
Full Steam
Flamingos wing it over hot spots in volcanic springs and skitter across burning shallows at Kenya's geyser-studded Lake Bogoria. The springs' fresh water emerges at boiling temperature— but it's all there is to drink. Where it cools to about 150˚F (65°C) downstream, the birds form orderly queues, waiting their turns to sip the hot water while they splash the lake's sticky alkaline residue from their feathers. Water elsewhere in Lake Bogoria, away from the springs, can be bitter and caustic and smell of rotten eggs. The salty lake sustains no fish and little vegetation besides spirulina algae. Few living things can endure such conditions, let alone thrive as the flamingos do. Yet the lack of competition for resources lets the flamingo population soar.
Sudden Death
In most of Africa, fish eagles eat what their name implies. But the harsh waters inhabited by lesser flamingos preclude much fish life. Fortunately for fish eagles, the valley's huge flamingo population provides easy prey. One fish eagle watched from the shore of Lake Nakuru for hours before it suddenly took to the sky, then dropped down onto the back of its victim. When a pair of marabou storks arrived to scavenge a share of meat, the smaller bird drove them away. Challenges by marabou storks—two other birds confront a young fish eagle over a carcass—are common on the lakes. The storks usually plunder other predators' food, or eat eggs in nests when they find them, but they'll kill adult flamingos too. Their method: They stab the birds to death with their bayonet bills.
Lake Nakuru's flamingo population is as ephemeral as a trail of footprints across its surface. The nomadic birds aren't vanishing. Guided by their needs, they simply move on.


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