How can a bird know that it has rained 100 or maybe even 600 miles away? That’s like a bird in North Dakota knowing that it rained in Idaho, because Montana is about 630 miles wide.

Somehow the banded stilt — a long-legged, long-beaked Australian shore bird — knows when it rains inland and desert salt lakes are flooded. That’s important to the birds’ survival because they flock to these flooded lakes by the hundreds to lay their eggs.

The lakes are important to the birds because they contain brine shrimp that hatch during the rains, a big food source for the mommy birds after they lay eggs. The eggs will weigh about half as much or more as the entire female banded stilt. Talk about weight loss, imagine weighing half as much as you do now.

Another odd thing is that the lakes only flood every 10 to 20 years. That doesn’t seem like a very good survival strategy, which may be one reason why the birds’ populations are declining. Another reason is that sometimes the lakes dry up too quickly in the hot desert sun. Also, silver gulls will eat the eggs.

So the odds of a banded stilt hatching and surviving seem pretty low.

Scientists were able to track the birds using small, solar-powered tracking devices they attached to captured banded stilts. Some bird conservationists are worried that if the desert lakes are mined, the banded stilts will lose important places to breed.

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What they weren’t able to figure out, however, is how the birds know when to fly to the flooded lakes. Could it be vibrations from thunder that they detect? Or is it a change in the air pressure?

— Brett French, french@billingsgazette.com

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