The Tasman District Council is warning people to be aware of nesting kārearea / falcons, which have been attacking unsuspecting walkers and mountain bikers in the Richmond Hills.
Council staff said there had been several reports of people being dive-bombed by the birds when straying too close to their nest.
In one case, a person had some of their hair pulled out. They did not require medical attention, but the incident gave them quite a fright.
Staff have located the kārearea nest in the upper Lodestone Valley and are monitoring it.
The area most in the firing line is the mountain bike track, Terminus, below the Fowler Road skid into Lodestone Gully.
Signs have been put up to warn people they could be targeted by the dive-bombing birds.
Falcons often begin defensive swooping behaviour within several hundred metres of a nest; within 50 metres, that escalates to the birds striking the intruder.
The birds can fly at speeds of more than 100kmh and can catch prey larger than themselves.
The council is asking walkers and mountain bikers who use the Lodestone Gully trails to steer clear of the area if they can until nesting season is over at the end of January.