Wellington, Sept 18 NZPA - Canterbury river visitors are being asked to watch their steps so they don't disturb rare riverbed nesting birds.

The survival of the birds, such as the rare wrybill, depended on successful breeding on the open gravel beds of braided rivers, Environment Canterbury said today.

In places like North Canterbury's Ashley River/Rakahuri, there were just a handful of breeding wrybills, Environment Canterbury's Environmental Protection team leader in Timaru, Roger Gould said.

Gravel extractors operating large vehicles on riverbeds had been reminded by Environment Canterbury to check for nests as the bird breeding season has begun.

Wrybill, black-fronted terns and black billed gulls were three species particularly at risk, but banded dotterels, stilts, white-fronted terns, South Island pied oyster catchers and other species were also nesting and feeding on Canterbury's braided rivers, Mr Gould said.

"We have already seen wrybill nests on the Rakaia, Rangitata and Ashburton Rivers," he said.

The other threats to the survival of the eggs and chicks included roaming dogs, vehicles on the river beds and people coming too close and keeping the adults off the nests, which meant that the chicks or eggs could die, he said.

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