Visitors to Abel Tasman National Park are being asked to report sightings of the toutouwai or bush robin.
Conservation organisation Project Janszoon would record sightings of the robin from Monday until the end of January.
Robins had been largely absent for about 30 years - but seemed to be making a comeback thanks to habitat restoration and predator control, programme director Bruce Vander Lee said.
"We've started to see an increase in anecdotal reports of robins sighted along the coastal track, so we are asking people using the track to let us know when and where they see the birds."
Robins were very sensitive to rat predation - if there were rats around, the robins disappeared, Vander Lee said.
"For the last 12 years, Project Janszoon and its partners have been controlling pests like rats and stoats, and restoring habitat through weeding and native planting.
"It's great to see these improvements supporting the return of taonga species like the robin, and we know that other forest birds like the miromiro/tomtit and riroriro/grey warbler will also benefit."
Native bush robins, or toutouwai. Photo: Ruth Bollongino / Project Janzoon
The information collected by citizen scientists would be used alongside data collected by monitoring bird calls, he said.
"We're asking visitors to look out for robins and report sightings from 6- 31 January. Anyone can take part, and we are hoping that people of all ages and park visitors from all over the world will enjoy being a citizen scientist and help make a difference to our knowledge of the park's robin population."
Robins were the same size as a sparrow, and grey with a white chest and long legs, Vander Lee said.
"The key thing is that they are very friendly and will stay close to visitors along the track - or walk right up to their boots."
People could report sightings while they were out and about in the park using the Abel Tasman App, or when they got home at [www.janszoon.org/reportarobin the Project Janszoon website].
"If you can take a picture and record the location, that will really add to the quality of the data collected."
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