Eggs of an endangered bird species have been shattered following disruptive Crate Day activities along a Canterbury river.
Several people zoomed up and down the Ashley River/Rakahuri in large vehicles on Saturday, crushing black-fronted tern (BFT) eggs and scaring young chicks.
Approximately 150 4WD vehicles were seen near the Okuku Bridge on Saturday morning, before moving up the river for 22km towards the Ashley Gorge.
Police and the Department of Conservation (DoC) were both present at entrances to the river.
"We spoke to people at two entrance points to the Ashley-Rakahuri and were pleased most drivers were receptive to our request for them to respect endangered birds breeding in the braided riverbeds," DoC operations manager Leeann Ellis told Newshub.
Ellis said conversations with drivers were mainly positive, and they were "keen to avoid nesting areas", amidst the peak breeding season.
However, she said despite "apparent good intentions" several nests, eggs and chicks were "impacted by flying stones".
DoC signage along the river warned of restricted areas where birds were nesting and hatching chicks.
"Some of the participants expressed concern for the birds, but little or none was shown," Ashley-Rakahuri Rivercare Group spokesperson Grant Davey said.
He said clearly signposted nesting areas were driven into, and protesters on the river were ignored.
Groups of people were seen walking and driving near young chicks hiding in the pebbles along the river.
"Black-fronted terns were wheeling around the vehicles and chicks were scurrying to get out of the way," Davey added.
He said pictures of the nests before and after the disruption show "unprecedented detail".
One photo shows a nest of crushed spotted eggs. Another photo shows a man bending over and pulling his pants down.
"BFT are very seriously threatened, in the last few years approximately one fledgling has been produced for every ten nests on the Ashley River," Davey said.
"This year the outlook is much better, but it is not helped by the actions of irresponsible people."
Human disturbance is one of the key factors to the species declining population in New Zealand.
Ellis believes such activities should take place in the late summer, when it is outside breeding season.
"It could be better for both birds and drivers," she recommended.