100,000 Pelicans: The Mystery of Pelicans and Lake Eyre

When Lake Eyre fills with water (roughly every 15-20 years), it becomes a giant pelican breeding colony.

For many years the question of how something like 100,000 pelicans find their way inland from Australia's coasts to Lake Eyre's tiny islands has been a mystery.

(How hundreds of birdwatchers also find their way to Lake Eyre is somewhat less of a mystery!)

John Read is an ecologist who's lived and worked around the lake for two decades. One of the most perplexing questions he's dealt with is how pelicans know when Lake Eyre is full.

In his book, Red Sand, Green Heart, he tries to solve part of this mystery.

Lake Eyre's Pelican Colonies

Australia's pelican population is somewhere around 300,000–500,000.

Most of the time, people just see the odd pelican or two scattered along the shore of coastal towns.

However, following inland floods, thousands and thousands of birds mass at breeding colonies hundreds or even thousands of kilometres away from the coast.

John Read was part of documenting the largest colony ever recorded at Lake Eyre South in 1990. In the first six months of 1990 following its flooding from local rains a year earlier, 100,000 pelicans successfully fledged as many as 90,000 chicks.

The pelicans flew inland, and roosted on the shores and tiny islands of the lake. They feasted on the explosion of fish and yabbies in the lake: Hardyheads, Yellowbelly, Bony Bream, Black Bream and Catfish.

This bonanza of food allowed a bumper breeding season for Australia's pelicans. This has been repeated in 2009-2011.

Even so, a single pelican needs to eat a lot of fish! Apparently, a single adult pelican can eat up to 500 Hardyheads per day.

(Hardyheads aren't very big!)

How Do Pelicans Know?

This brings me to the mystery of how the pelicans know when Lake Eyre is full.

Read relates in his book that some ornithologists thought that pelicans could detect sonic or ultrasonic vibrations of storm fronts that were hundreds of kilometres away.

However, he dismisses this, as the presence of storm fronts doesn't necessarily mean a major flood event.

He then looks at theories claiming that the birds can smell the fish in the lake. This is easily dismissed, as it's impossible for birds to smell fish thousands of kilometres away.

What he suggests is that the pelicans might be like bees.

By this, he means that some pelicans act as scouts, who criss-cross the country, and when they find inland floodwaters, return to communicate the news to other pelicans.

He supports his case with his own observations of:

• the pelican waggle-dance, which he likens to the same kind of dance the bees do
• the fact that pelicans have a 2.5 (huge) wingspan
• pelicans can easily fly long distances

Whilst this might not yet be the widely accepted theory about how the pelicans come to know that there's food and water inland, it's certainly a lot more plausible and robust than 'feeling vibrations' or 'smelling the fish'!

Red Sand, Green Heart is a fascinating book that I've now read several times. If you've taken a flight over Lake Eyre and seen the huge pelican colonies, I recommend picking up a copy and giving it a read.