Wildlife Hospital Dunedin manager Jordana Whyte said that despite the exact numbers of eggs and chicks from all nesting sites not yet being known, signs pointed towards a decline.
"Having any decline is pretty significant. There’s just not that many nests."
There were no "definite" numbers available to her yet, but over 165 chicks were expected to be born and the hospital expected to hatch between 20-30 eggs this season, she said.
"It does seem like every site that I've heard reporting in has definitely had at least a minimum of one less [egg] than the previous season and some are down by a few."
This decline was of concern, she said.
"Hopefully they’re having a good season out there and we get more chicks."
Mating took place in September and October and eggs hatched in November and December.
The hatchery at the wildlife hospital now had two eggs incubating from a North Otago hōiho colony, she said.
Initially it was thought the eggs were infertile, but there was a possibility they were in fact fertile.
"There's no risk in incubating them to see if they may hatch."
These eggs were kept incubated in a specialised hōiho hatchery at the hospital.
The hatchery had been "trialled" the past couple of years and would now be used annually, Ms Whyte said.
"It's good that we have the capability so we can try these things now."
The arrival of the eggs from the Green Island hōiho colony was expected this week and chicks were expected to begin hatching from Friday.
Speaking at an Otago Regional Council meeting last week, Ms Whyte spoke on the upcoming breeding season.
A 90% success rate was expected with chicks incubated at the hospital, she said during the meeting.
"Ninety percent of the chicks that we receive we are able to nurse through their vulnerable disease period and get them back out to where they belong."
Last year, 178 hōiho chicks were admitted to the hospital during November and December for hand-rearing to protect them from diseases.
