Restoration work on Henderson's Opanuku Stream has likely encouraged the bats to return to the suburbs.

Endangered native long-tailed bats have been found in suburban West Auckland for the first time in more than 15 years.

The bats were recorded on March 24 during a Bioblitz event where surveyors spent 24 hours recording living species in the area, Auckland Council's senior biodiversity adviser Ben Paris said.

He said the bats are about as big as a thumb and weigh the same as two $2 coins.

JACQUI GEUX/WAITAKERE RANGES WES MPHS Project Twin Streams Oratia and Opanuku community co-ordinator Tina Samuelu with the bat reader.

The Department of Conservation's website said New Zealand bats were "rapidly" heading towards extinction because of rat plagues.

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GERARD KELLY/SUPPLIED Long-tailed bats are "rapidly" heading towards extinction because of rat plagues, DoC's website says.

Long-tailed bats in particular were under threat because of clearance and logging of lowland forests, cutting of old trees for firewood and predation by cats, possums, rats and stoats, the website said.

The bat signal was picked up near Opanuku Stream around Corban Estate Arts Centre in Henderson, McLaren Park Henderson South Project Twin Stream Oratia and Opanuku community co-ordinator Tina Samuelu said.

"They came through pretty strong. It's like a clicking sound, but really fast," she said.

Paris said they were able to tell that what they recorded were long-tailed bats because the detector was set to 40khz, a frequency the bats used for their echolocation (sound navigation).

"The special bat detectors have microphones that pick up the echolocation calls that we can't hear, and they convert them to clicks and buzzes we can hear," he said.

​Paris said the bats had a "strong hold" in the Waitakere Ranges, but hadn't been observed in Henderson since the 1990s.

Auckland Council had tried to find evidence of bats in a 2012 survey around the lower Opanuku Stream with no success, he said.

"West Aucklanders could have long-tailed bats flying by their backyard, local park or school and they just didn't know it."

Paris said long-tailed bats used streams like highways, and travelled along them at speeds of up to 50kmh, eating tiny insects that come off the water.

He said the work of those restoring Opanuku Stream had helped encourage the bats to come down from the Waitakere Ranges.

"Healthy stream habitat produces lots of insects for long-tailed bats to eat," he said.

"The more of this sort of stream restoration and pest control that can be done by the community, the more likely we will see bats return to our urban areas."