Why Do Owls Hunt At Night?

Tawny Owl David Cobham Sparrowhawks lamentMy love of birds of prey was kindled early in my life when I was staying with my grandparents. I was about four years old and my younger brother, Richard, had just entered the world. I was put to bed early as there was a party to celebrate his safe arrival. To pacify me my Mother had promised me an ice cream. I fell asleep and woke to find my room light as day, a full moon shone through the open window. I looked over at my bedside table. Yes, there was the ice cream – melted! Why hadn’t they woken me? I heard a scratching sound and saw, on the window sill, a large owl. For a moment we looked at one another. Then, as silently as it had arrived, it swept off into the moonlight.

I think nearly everyone must be familiar with the Tawny Owl. Who has not heard the “tu-whit”call of this owl on an autumn evening. If you’re lucky you may have seen one perched on the branch of a tree next to the trunk trying to make itself as thin as possible to avoid the attentions of small birds intent on mobbing it. Once spotted, tits, finches, blackbirds and thrushes are ruthless in telling the owl to move on. When it does so it reveals itself to be the largest of our native owls.

Recently Dave Culley, who filmed that masterpiece, “The Secret Life of the Sparrowhawk”, has focussed his camera on the Tawny Owl, a pair of which had taken over the Sparrowhawk’s territory on the island on a canal where Dave lives near Northwich in Cheshire. Although Tawny Owls do move around occasionally during the day all their interesting behaviour occurs at night. Technically it was a tough choice to have made. But Dave knew their flight paths, where they sat and where they caught their prey, He lit all these areas and positioned cameras accordingly. There were 7 fixed cameras, remote controlled, and 4 cameras which Dave operated.

For the Tawny’s nest site Dave dragged ashore the trunk of a willow tree that was floating in the river, dried it out for 6 months and then carved out a hollow nesting chamber in it. This he attached to a willow tree in his garden. The owls took to it immediately. The first thing he noticed when he started filming was that the Tawny’s predation techniques were totally different from those of the Sparrowhawk. The Sparrowhawk during incubation and raising of their young does not predate in the neighbourhood of the nest site. They do this so that their young, when they fledge, have plenty of unwary prey to feed on. The Tawny Owl, on the other hand, from day one of incubation, takes fledgings from song birds nesting in its territory. When the song bird lays again they’ll take those as well. They take an incredibly wide range of prey from Wood Pigeons, Magpies and even Grey Squirrels down to the smallest of our song birds. They raised two young and I was amazed to see that they ate slugs and later Dave filmed them plunging down from a branch to catch frogs in a watery patch below the nest site. A truly remarkable film and can be ordered direct from Dave Culley at www.sparrowhawk-island.co.uk.

The Secret Life of The Tawny Owl_Chris Packham_David CobhamIf you still have a lust for more information about owls I have no hesitation in recommending Owls in the Collins New Naturalist series by Mike Toms. It is long overdue but here it is at last and Mike has made a cracking good job of it. The book is broken down into seven sections: Introducing Owls, Food and Feeding, Breeding Ecology, Movements, Mortality, Owls and Humans and a Guide to British Owls. Mike starts by recounting his first sighting of an owl, a Barn Owl, whilst he was out on his paper round. Who has not been entranced by the Barn Owl’s heart-shaped almost human face.

In the Introducing Owls section I was gripped by a section on the nocturnal habits of owls. Why do owls hunt at night? They are superbly adapted to it now but what in the past prompted the change from daylight to night hunting. Mike puts forward several compelling reasons. Owls prey on items, such as voles, which are more active at dawn and dusk. Hunting at night means that there is no competition from other predators. Finally, because of their slow flight quartering a field in search of prey they would be vulnerable to daylight predators such as Goshawks. It was safer to hunt at night.

In the chapter on Owls and Humans Mike Toms pays tribute to Colin Shawyers epic 1987 Hawk Trust survey “The Barn Owl in the British Isles; its Past, Present and Future” which showed that it had become one of our rarest breeding owls. Many people became aware of the Barn Owl for the first time and wanted to do everything they could to help it. Nest box schemes and co-operation from farmers halted the decline. As Mike Toms puts it: “We have dispensed with the fear and suspicion formerly surrounding them and take them into our hearts.” Mike Toms’s book on Owls is fat with fascinating facts that will satisfy the most discerning reader and Robert Gillmor has complimented the text with an outstanding illustration of a Barn Owl hunting over a reed bed.