Short-eared owls appear to be nomadic, breeding almost prolifically in suitable habitat in some years, yet in others appearing to be absent. Adults owls can be seen flying during daylight hours when they have dependent young, but at other times they can be largely nocturnal, making the population hard to monitor. The best evidence that we have suggests that the population has declined, perhaps by as much as 50%. The reasons underlying these changes are poorly understood, but recent advances in technology have presented new opportunities for research.

Source: Short-eared Owl Tracking | BTO – British Trust for Ornithology