Nearby open grassland is essential, however, for hunting. Barn owls are almost never found in deep forests or mountains. Declines in the barn owl population are directly related to climatic changes, pesticides, and changing agricultural techniques. A change of climate in northern regions is causing snow to last for longer periods making winter survival difficult for the species. Unlike other birds, barn owls do not store extra fat in their tissues that help them survive harsh winter weather.
Many owls die during freezing weather or are too weak to breed in the following spring.
Pesticides have also contributed to the demise of the species. For some unknown reason the barn owl suffers more severe effects from consuming pesticides than other species of owls. These pesticides are often responsible for eggshell thinning in females. With the average lifespan of an owl being two years, the reproduction process is already slow without the complications of weak eggshells. The last major factor limiting population growth is modern agricultural methods.