As a nearby resident watched, the harrier was soaring in mid-air when "out of the blue, a tui charged him" and "slammed into the harrier so hard" it broke its wing, Dunedin Wildlife Hospital veterinary surgeon Dr Lisa Argilla said.
After the predator "just suddenly dropped out of the sky", the resident looked after the injured bird overnight on June 29, and contacted the Department of Conservation, which contacted the wildlife hospital at Otago Polytechnic.
"Luckily the fracture should heal well with just a bandage to stabilise it," Dr Argilla said.
The harrier was "enjoying great food and pain killers" and spending some time in hospital "to think about the story he wants to tell his family when he is released".
Tuis could be aggressive in protecting their territory, she said.
Hospital veterinary nurse Angelina Martelli said the hawk would spend another three weeks in hospital before rehabilitating at Oxford Bird Rescue, northwest of Christchurch, and being released into the wild.
