They live in dense forest and are used to flying through small gaps between branches and brushing leaves out of the way - given the choice they’ll they go under or through obstacles rather than over, to reduce the risk from hawks. Plus they live on berries and prefer the overripe ones, which are often fermented, so they’re prone to flying under the influence of alcohol. Because of all this they manage to combine impressive levels of clumsiness with being incredibly manoeuvrable for big birds - they’re fun to watch in flight, because they DGAF. It also means that anything you can see through, a kereru (native name) is likely to treat as permeable.
Unless you’re prepared to invest in plate glass, broken windows from kereru are just an occupational hazard of living surrounded by forest, in NZ.