A kākāpō on Anchor Island has died of suspected heat stress, the first such death in more than 20 years.
The parrot, named Blake, died after he had been captured for a routine transmitter change last Tuesday.
Department of Conservation scientist Andrew Digby said all kākāpō were fitted with transmitters that were changed every year.
"It's a normal procedure which we do regularly and have been doing for more than 20 years. We've done 6500 captures," he said.
He said being caught may have stressed Blake, but the extreme heat and dryness exacerbated it.
Blake was panting during the procedure and although the team tried to cool him down it was too late.
The death surprised Mr Digby, but he said Blake was "very fat".
Very sad news: #kakapo Blake has died on Anchor of suspected heat stress following a transmitter change. Team shocked by this: first time in >20 years & >6500 captures. Very hot, dry weather in Fiordland, and Blake was fat. Measures in place to prevent this happening again. pic.twitter.com/ie1J8c7rkf— Dr Andrew Digby (@takapodigs) December 4, 2017
"Males at this time of year put on a lot weight because they're coming up to the booming season ... he'd put on a lot of weight and they develop boom sacs as well, so it was a combination of things."
Mr Digby said despite that, Blake was in top condition and heavier birds were considered healthy.
The Fiordland region has had no significant rainfall in the past two weeks and with temperatures reaching 27°C, creeks and streams had dried up.
"This is the sort of conditions you'd expect in February," he said.
Kākāpō are very rare with only about 152 left, about half of them male. There are 62 kākāpō on Anchor Island.
Mr Digby said that even though the population had grown by 25 percent in the past year, it was a big loss.
"We know all these birds individually, the team always takes it hard when one dies," he said.
Mr Digby said that the team would learn from the incident, and will not be catching the birds in hot weather again.
Transmitters are essential to #kakapo #conservation - without them, pop would be much smaller. So transmitters will continue to be used, but extra care taken to avoid heat stress & similar issues in future. Sad times, but we'll learn from this. pic.twitter.com/C7jybNutmW— Dr Andrew Digby (@takapodigs) December 4, 2017
The hot summer may also make life difficult for kiwi.
Department of Conservation scientist Hugh Robertson said the warmer weather made it more difficult for kiwi to dig up insects which burrow deeper to reach damp soil.
The birds run the risk of dehydration, as they get most of their water from insects, and some may drown in cow troughs and ponds as they seek out water.
Mr Robertson is urging farmers in areas with kiwi to put in ramps, so the birds don't get stuck.
Meteorologist Hannah Moes yesterday told RNZ the ridge which has been over the country for a couple of weeks is starting to move east, but the hot weather should stick around for the rest of the week.
"There is a bit of a respite for the eastern centres on Wednesday, a very weak southerly will come through but it will still be warm with temperatures in the 20s, just not as high as 30.
"Comparing temperatures from this year to last year, this year we are in the late 20s to early 30s, whereas at the start of summer last year temperatures were in the mid to late teens."
Temperatures throughout New Zealand are also an average two degrees warmer due to La Niña, which causes high pressure.
Ocean temperatures off the West Coast are reaching levels that are 6.5 degrees more than normal, and is expected to rise even further his summer.
Niwa meteorologist Ben Noll said things could get even hotter.
Mr Noll said high pressure made the ocean more stagnant, allowing it to warm up quickly.