A few days ago I went to pick up yet another kereru (NZ native wood pigeon) that had been found motionless on the ground near a house in Matarangi. (We don't usually collect birds but let the public drop them off).
After carefully scooping the injured bird up with a towel and placing it in a box in the car, I had a look around and noticed so many more huge houses with big windows that had been built recently.
In the last few weeks Kuaotunu Bird Rescue Trust has admitted 11 kereru after striking windows or buildings. So far only one of them has been able to be saved.
When a small bird hits a window it may just be concussed and will be fine if left to rest in a quiet place in a box. However, as the saying goes, the faster you drive the bigger the mess. It's the same for bird size. The bigger the bird, the more damage.
Often when rescuers ring us, they tell us that the bird is fine and has no injuries but won't get up.
As a general rule wild birds are very hard to get close to or to capture when they are healthy, so 99% of the time any bird that is able to be approached and caught by a human will have some sort of injury, even though this may not be detectable from the outside.
Birds also have a preservation reflex. This is an adaptation to survival in the wild so as not to look vulnerable to predators (no, that bird is not friendly). Hawks are very good at pretending they are fine and will freeze, hoping that they will be left alone.
Unlike mammals birds also show no or little pain. So most birds that can, will still fly away from us human predators, even though they may have injuries sustained from hitting that window.
Kereru are heavy birds (between 600g and 900g) and when they hit a window or glass balustrade they hit it with their chest first. Often people say they heard a loud bang and found a kereru on the ground or deck.
When the rescuer tells us the bird is chirpy and feisty, we know it is trying to show that it is OK and still ready to fight us, even with the injuries it may have sustained. These range from multiple soft tissue injuries to fractures to the bones around the chest area. Typically they include crop rupture, bleeding around the heart, and fractures or dislocations of the coracoid, scapula, keel, and clavicle bones. Usually, there are fractures to multiple bones, which can then puncture not only surrounding muscle but also organs such as lungs and heart. Head injuries and fractured beaks are not uncommon either.
Most of these injuries cannot be seen from the outside. These big birds need to be stabilised with pain relief and fluids. Then we usually X-ray them to find out how severe the injuries are.
The good news is you can try and reduce the danger of window collisions for birds by placing decals on your windows (or not washing them as often?). The decals stop the reflection birds see when trying to fly through. For more information please see Prevent Window Strike - projectkereru.org.nz.