About 25,000 pairs of mating seabirds have lost their home near Kaikoura following Monday's massive magnitude 7.8 quake.
Landslides wiped out the breeding ground for Hutton's shearwaters, and Department of Conservation ranger Mike Morrissey says it will take years for the birds to recover.
"There are rocks still coming down up there. When we were up there, there was still rockfall, big clouds of dust," he told Newshub.
"The birds are no longer there, anyhow. It's certainly very devastating for the overall population."
It's estimated there are only about 100,000 shearwaters left, and the quake might have killed thousands of them. The bird only breeds in New Zealand, in the Kaikoura Ranges.
"It's completely destroyed, there's nothing there - it's just sheer rock," says Mr Morrissey.
"It didn't look too bad until you got up there, then once you got there...you can see what happened. Half the birds that are on the nests, sitting on the eggs now, they would have been just wiped out."
Forest & Bird said in a statement: "geological events like this could wipe out 10 to 49 percent of the Hutton's Shearwater colony - depending on timing of breeding".
A special seal sanctuary just off State Highway 1 near Kaikoura was also wiped out in the quake, with the number killed yet to be established.