At Petone, the sea and the air were filled with birds, feeding on shoaling fish. Eight Gannets plunge-dived from ten to fifteen metres above the water. Below the gannets, White-fronted Terns dived from three to five metres. Black-backed Gulls, Red-billed Gulls and Black-billed Gulls hovered in tight knots of heads, wings and feet, swooping like spoons into the water. On the water, Little Black Shags and Spotted Shags dived for prey.
An Australasian Gannet in action, Petone (photo Peter Hodge © All rights reserved 2013)
But the birds that stole the show were the Fluttering Shearwaters. Great numbers of shearwaters (some 1000 birds) gathered just offshore, rafting, flying, and surface feeding on fish. The shearwaters searched for their prey by paddling forwards, their heads below the water. When the birds saw prey, they arched up and duck-dived, half-opening their wings and using these for propulsion.
After a while, the shearwaters would sense prey elsewhere, and they would take off, getting airborne by flapping hard and skipping across the water, using their webbed feet to push along and off the water. It's almost as if the birds can run on water, for a few seconds at least.

Fluttering Shearwater getting airborne (photo Peter Hodge © All rights reserved 2013)
The most intriguing aspect was the way the Fluttering Shearwaters located their prey. I watched the birds raft together in their hundreds. Then the birds would take off, wheel, and fly to where fish were shoaling. It was like they'd received some signal - 'hey, the fish are over there'.
If this is the case, what sense, or senses, do the Fluttering Shearwaters use to locate their prey, often at some distance (several hundred metres) and in choppy and murky water? What's the nature of the signal they receive, and how is it transmitted between the birds?
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