A colony of 300 critically endangered birds has found an unlikely place to nest - in the middle of a paddock full of dairy cows.
The discovery was made late last year - black billed gulls building their nests on the Canterbury farm and then successfully raising their chicks, oblivious to the cows grazing nearby and the odd shower from a pivot irrigator.
Black billed gulls nesting alongside dairy cows on a Canterbury farm. Photo: Supplied
Ornithologists were amazed to see the birds nesting in an area they had not been seen in for three years.
Last year's unusual discovery was revealed on Thursday at a seminar organised by Braid - a group dedicated to saving the South Island's braided rivers and the creatures that live there.
In a place like the Canterbury Plains, which have been more intensively farmed than almost anywhere else in the country, the rivers are a last refuge for many birds including black billed gulls.
But in a reminder to farmers that the gulls were there first, these plucky birds have started to take back what was once theirs.
Braid chairperson Nick Ledgard said they were initially attracted to the paddock by the prospect of freshly dug worms.
"They will only nest on bare ground, and it just so happened that he [the farmer] was working up that paddock which attracted them for feeding reasons, so they thought why don't we stay there.
"The images that Grant [Davey] took showed them surrounded by green grass, but it wasn't all green grass when they arrived there."
Black billed gulls oblivious to the cows grazing nearby and the odd shower from a pivot irrigator. Photo: Supplied
Conservationist Grant Davey said with the co-operation of the farm manager they put up a temporary electric fence around the colony to protect it from the cows.
Otherwise the farm was allowed to continue running as normal.
"The irrigator would just pass overhead every week or so, cows came in and out of the paddock and the birds didn't seem to be disturbed at all... we haven't seen this sort of thing up here."
One reason the birds may have chosen the paddock was that their preferred nesting site of the nearby braided bed of the Ashley River was overgrown with weeds, said Nick Ledgard.
"Without a doubt we've seen an exponential increase in weeds. Lupins initially but gorse and broom etc. etc. and that is most definitely having an affect on the birds both feeding and breeding in the braided rivers."
There were advantages to setting up a colony in the middle of a farm paddock which was relatively peaceful compared to a river easily accessed by people walking their dogs and other threats, Mr Davey said.
But they would make efforts this year to try to encourage them back to their former home.
"We're planning on clearing some islands in restricted areas where the birds have been known to breed in the past. We can't possibly clear the whole river but we can clear large enough areas so we expect some of the birds will come back."
But while some species are surviving on the plains despite what civilisation might throw at them, others are not doing so well.
Department of Conservation chief science advisor Ken Hughey said a recent report from the Parliamentary Commissioner for the Environment found every braided river in Canterbury and Marlborough was being negatively affected by human activity, from their source to where they met the sea.
While many of these rivers were in good condition just a few years ago, this was no longer the case, he said.
Professor Hughey said the biggest human impact was still to come in the form of climate change.
This would bring increased rainfall in the mountains and a subsequent rise in the number of floods on Canterbury's rivers which could force birds such as the black billed gull out of the braided river beds for good.