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Natural Scotland: Homes for Owls on Loch Lomond

In his guest blog post, James Elliott, Estate Ranger for Cameron House on Loch Lomond and The Carrick Reserve, Loch Lomond, tells us about barn owls and how to make homes for them.

Carpentry is not something I have much experience in, but when it comes to giving one of my favourite bird species a home, I am willing to give it a shot! And so last month I constructed two barn owl boxes for the Carrick and Cameron House estates.

Barn owls have occupied a special place in the human imagination for millennia. With their ghostly white appearance, silent flight and piercing shriek beloved by horror flicks, no other bird has such a supernatural reputation. This aside, the barn owl is a fascinating and highly evolved predator. They do not hunt in woodland but in open areas of rough grassland over which they fly several metres above the ground searching for prey such as field voles and wood mice.

The physiology of the barn owl is highly adapted to enable it catch these small mammals. They possess large wings relative to their body size that enable them to fly very slowly over the terrain as they scan for prey. Their super-soft feathers deaden the sound of air moving over their wings which not only gives them a greater degree of stealth but also enables them to hear better, a sense which requires little improvement!

With the ears placed asymmetrically either side of the facial disc, the owl is better enabled to pin-point the exact location of a sound source allowing them to hunt in total darkness. In low-light conditions the barn owls eyes are twice as light sensitive as our own favouring them with a much brighter image that is perfect for detecting small objects moving along the ground. For the final kill the barn owl has sharp talons on the end of its long legs that allow it to catch prey through deep vegetation.

After assembling my boxes in the workshop it was time to select a suitable tree to locate them. With their large open areas and swathes of deep rough, golf courses can provide good habitat for barn owls. With the help of raptor enthusiast Alex Nicol, a suitable tree on each estate was selected and all that was left to do was haul them up. For this task I was aided by nest box veteran and National Park ranger Steven Kenney. If I thought building the boxes was the hard part I was sorely mistaken - they weigh a ton!

Eventually we got them up though, and now I look eagerly for telltale droppings and owl pellets at the base of the trees every time I walk past. They are unlikely to attract occupants this year however as the owls have generally decided upon their breeding locations by late winter and it may be several years before they are used.

Now, in early spring, the owl pairs will be spending time in and around the nest, the male strengthening the pair-bond by passing food to the female and helping her get into breeding condition. Five to six eggs are generally laid in April-May, the female making a small scrape in the previous years’ debris and incubating them for around a month. For this reason the base of the boxes are filled with woodchip.

The eggs hatch in the order they are laid and there can be as much as three weeks age difference between the oldest and youngest. Older chicks have a better chance of making it to adulthood, although the survival rate is heavily dependant on the number of small mammals available for the parents to catch.

Voles, the primary food species, have a population that peaks and troughs in four-year cycles meaning a ‘good vole year’ will raise the population of barn owls along with that of other raptor species.So here’s to plenty of voles and plenty of barn owls for this breeding season and, with luck, new residents in our boxes for the next.

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