Last year, a group of about 70 four-wheel-drivers ignored conservation warning signs and drove up and down the Ashley River where endangered birds were nesting.
Crate Day has become an unofficial holiday that is celebrated on the first Saturday of December, with participants encouraged to finish a crate of beer over 12 hours.
In Canterbury, ornithologist Niall Mugan recently discovered an abandoned black-fronted tern colony nest site, on an island in the Waimakariri River.
It was surrounded by smashed beer bottles, which appeared to have been thrown from the mainland about 25 metres away, and Mugan said it was likely that caused the birds to leave.
"These birds are incredibly sensitive to any disturbance so anything like that is going to put them off, especially when they are just about to lay ... so we lost, at the very least, five pairs of black-fronted terns, maybe more.
"It is disappointing because these birds had chosen a good place that was away from most predators and away from the bank and they had an opportunity to breed successfully this year and now they have to try and find another place."
He said it was important young people were able to enjoy themselves, but it did not have to be at the expense of rare, nesting birds.
From early September to the end of January, threatened native birds such as ngutu pare/wrybill, tūturiwhatu/banded dotterel, tarapirohe/black-fronted tern and tarāpuka/black-billed gull breed in the dynamic South Island braided rivers such as the Ashley River/Rakahuri.
"Don't assume that an open, braided, river has got no birds in it, within at least 200 or 300 metres of an open gravel area, you can expect to find one of New Zealand's rare breeding birds and they are birds that are designed to hide in these habitats."
The Department of Conservation (Doc) has also issued a plea asking four-wheel-drivers to keep off riverbeds during bird nesting season.
North Canterbury operations manager Leeann Ellis said it was aware of three sites with nesting birds in the upper stretch of the Ashley River, above the Okuku River confluence.
In past years, a large number of vehicles had gathered on the Ashley River for Crate Day, and Doc was asking people not to drive on the riverbed, or to wait until the nesting season was over in February.
Rangers would be out at river access points on Saturday to make people aware of the nesting birds.
"If there were issues, it would need to look at options like blocking access or introducing bylaws prohibiting driving on the river at certain times of year."
The Ashley Rakahuri Rivercare Group was formed more than 20 years ago to protect riverbed birds and their habitat and member Judith Hughey said four-wheel-drive vehicles affected the survival chances of endangered braided river birds.
She said the group would be disappointed if vehicles gathered on the river for Crate Day, again.
"Fast, noisy and aggressively driven vehicles can cause birds to abandon nests, kill chicks, smash eggs and leak contaminants in the river which could render the riverbed, shallows and the river itself unliveable for larvae, insects and small fish that birds rely on for their daily food."
Environment Canterbury parks and forests manager Chuck Dowdell said the birds, along with their nests and eggs, were well camouflaged against the river stones and were very hard to spot unless you were up close.
The regional council manages the area of the riverbed that runs alongside the Ashley Rakahuri Regional Park, downstream of the Okuku confluence.
It has worked with the Ashley-Rakahuri Rivercare Group, to install warning signage and concrete barriers around this area of the river ahead of each nesting season.
There will also be a police presence at the Ashley River this Saturday, with officers reminding drivers not to get behind the wheel after drinking, whether on road or off.
A study earlier this year found ED admissions for alcohol-related harm in one part of the country were double that of a normal weekend.
Combined 4WD Club chair Mike Sheppard said it was disappointing to see some four-wheel-drivers behaving poorly in previous years as it reflected badly on responsible drivers.
"The club promotes responsible four-wheel-driving and works with land managers around access for their members and maintenance of tracks and facilities, and anti-social behaviour from drivers puts all of this at risk."
