Barn Owls are one of the many wildlife stars of BBC Winterwatch, and close neighbors in the BBC studio at RSPB Arne Nature reserve. The RSPB’s Tony Whitehead share’s a few secrets about these well known birds …
Seeing a barn owl is always memorable. I can easily recall a whole list of 'barn owl' moments. Driving down a Devon Lane by the Teign estuary and having one follow the hedge by my side, looking almost egret like with its white plumes glowing in the light of the moon. Watching a couple of birds hunt by day over the RSPB's reedbed reserve at Ham Wall near Glastonbury. Or a single bird late one winter afternoon flying low over the marshes at Cley in Norfolk.
Photo 1: Barn owl in flight by John Bridges (rspb-images.com)
Barn owls are not difficult to identify with their white heart shaped face, buff brown back and wings and those ghostly white under parts. Females have slightly more streaking than males, but they are difficult to tell apart 'in the field'.
Photo 2: Barn Owl by Terry Bagley
In flight they are rather 'buoyant' and slow, often dangling their legs while hovering in a kestrel like manner, scanning the ground for prey. They are very methodical in their hunting - careful flying in straight lines up and down a patch of land. They are also quite vocal, especially in the breeding season.
Photo 3: Barn owl on fence post by Ben Andrew (rspb-images.com)
In the 18th century the father of wildlife writing Gilbert White wrote of barn owls that they 'often scream horribly as they fly along'. This is the common call of the barn owl - a long drawn out shriek, heard both from flying or perched birds, most frequently from the male. The Hampshire parson went on to describe how villagers at Selborne, on hearing the bird `imagined the churchyard to be full of goblins and specters'. They also hiss, snore and yap. If disturbed close to the nest, birds often snap their beaks in alarm.
Barn owls are birds of open country where there is prey-rich grassland and access to suitable nest sites. Their foods of choice are voles, mice and rats but they may also take a wide range of other animals including birds and even bats. Although they are largely nocturnal they may at times been seen feeding during the day, especially in winter and when they have young in the nest.
Their nocturnal habits and choice of prey means that they have evolved some fairly sharp senses. First of all, they have large forward facing eyes. Their size helps gather light in poor conditions and their position means they have good stereoscopic vision for judging distances accurately - compare this with birds such as pigeons and thrushes whose widely spread eyes limit their stereoscopic view.
They also have very sensitive hearing that enables them to pick up on the slightest rustle in the grass. In fact, at night they will rely more on sound than vision to pinpoint creatures. Alongside their sensitivity, their ears are also placed at different heights on the side of their head. This means that sound reaches one before the other and helps them calculate the distance and position of prey.
Finally, in a wonderfully subtle adaptation, the leading edge of the barn owls wing is covered with special fine feathers. These enable the bird to cut the air silently when in flight and not give their position away to potential meals! Once caught, the mouse or vole is carried off to be devoured. The indigestible parts of the animal, bones and fur, are brought back up as pellets which can often be found in profusion around the bottom of the birds feeding site. Analyzing them is one of those favourite activities for young and old alike - there's often a palpable sense of anticipation before you open one in front of a group to see what the owl had for dinner last night!
Photo 4: Barn owl at nest site with rodent by Stanley Porter (rspb-images.com)
Barn owls are hole-nesting creatures. They use either natural sites, such as in trees, or, as their name suggests in barns or other suitable buildings. They will also take to nestboxes.
Photo 5: Barn owl with young at barn nest site by John Markham (rspb-images.com)
They are not great nest builders; with the female simply laying her eggs on a small pile of pellets (nice!). First eggs are laid in March. Because incubation starts with the first egg (as opposed to when the clutch is complete) development is unequal. This means that when hatching starts thirty days later, the young range in age and therefore size. In some cases there can be as much as two weeks difference between eldest and youngest sibling. Now, it might be anticipated that this would mean the big birds would simply dominate the smaller ones, but not so - the older siblings will actually help feed the youngsters in the nest. Unless food is short - when sadly older siblings may eat younger ones, as was filmed famously on Springwatch a couple of years ago. Fledging takes quite a while, but by 50 days the young leave the nest. If time and resources allow, the pair may raise two broods in a season.
Photo 6: Barn owls by John Markham (rspb-images.com)
The barn owl has faced its fair share of problems over past decades and its population is only one third of what it was in the early parts of the 20th century. These declines are largely due to loss of prey rich habitat and loss of nesting space, the former being more significant than the latter. For instance, traditionally managed hay meadows were a boon for barn owls. The conversion from hay to silage, and the consequent loss of 90% of meadows since the 60's has seriously impacted on the numbers of small mammals and consequently on those creatures higher up the chain such as our barn owl. Alongside this, many old trees with suitable nest holes have been removed ('tidied up') and derelict barns, ideal nesting spaces, are still being converted to houses.
However, its not all doom and gloom. With increasing numbers of landowners putting in place wildlife friendly farming methods on their farms, barn owl numbers are increasing in many areas. This is a good example of how wildlife and efficient food production need not be mutually exclusive. If the trend continues we are likely to enjoy more frequent views of this most popular of birds.
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