That's’ according to this article which highlights how reliant the birds are upon human intervention. The birds have been brought back from the brink of extinction by a programme to install nest boxes. However, without a continued conservation effort the birds could be at risk. Between the 1930s and 1980s numbers of barn owls fell by as much as 70% with only 4,000 breeding pairs of birds. It is thought that the installation of nest boxes has now halted the decline and in some cases it has been reversed. Barn owls are largely reliant on areas of ungrazed and unmown grassland where their favourite food field voles like to live. With less of this type of habitat available barn owls tend to hunt alongside roadside verges which is unfortunately a risky pursuit with large numbers being killed by cars every year. Whilst the nestbox scheme is encouraging it appears it needs to be an ongoing project in order to save the species.