Window strike is the most common reason for the kererū ending up in its hospital, with hundreds over the past few years - but they're not the only birds taking a hit.
Survival rates were also down due to the severity of the injuries and people treating the kererū believe double glazing could be the problem.
Dunedin Wildlife Hospital general manager Suzanne Stephenson told RNZ's Checkpoint programme today number of kererū deaths was rising.
"When we started eight years ago ... we saved about 64 percent of the kererū that we saw - that's sort of 37 out of 57 - we were able to give a second chance and get back out there into the wild.
"But last year that basically halved, we're down to 34.7 percent or 17 out of 49 birds."
Modern homes with bigger windows and double glazing could be to blame for the rise, she believed.
"Now the difference is down the track, we used to have single glazing and that glass had a bit of give, so if a kererū saw a line of flight through your windows it would possibly fly through that, it would break the glass, but with an injury that was probably quite survivable.
"... Obviously, you know double glazing protects us, keeps us warm, but what it does is give a very hard surface and our very large wood pigeons of course, some of them weigh up to about 650 grams, hits that with great force."
Stephenson said she understood the practical use of double glazing, but encouraged people to work together with native wildlife to reduce serious injuries.
Though birds had far greater eyesight than human, she said they see a flight line path through the window and reflections also prove difficult.
The Dunedin hospital had a couple of injured kererū being looked after, but there were also other types of birds being affected, she said.
Shining cuckoos and kingfishers were also renowned for window strike.
The size of the kererū didn't help with injuries, with the force of impact being larger as a result.
"They're the largest species of pigeons in the world and I think any bird that goes straight into a window, no matter what its size, that impact is going to be huge for them," she said.
"People will tell us that they've seen a bird on the ground not moving and they've watched it for a couple of days to see if it's okay."
It was not natural behaviour and she advised people to ring the Department of Conservation hotline as soon as possible 0800 362 468 (0800 DOC HOT).
