Bringing the owl back to town

Notes from Nature: Mar. 2010

Columns | R S Hughes | March 2010

Not many urban centers can boast a pristine 200-year-old oak forest within their city limits. Just a short ride on public transport from Vienna’s center, though, brings you to just such a place: The Research Institute of Wildlife Ecology in Vienna’s 16th District, where I’ve come to meet Dr. Richard Zink.

These aged, stately oak trees make up some of these south-easternmost reaches of the Vienna Woods, a UNESCO designated biosphere preserve since 2005. This area in particular provides an ideal habitat for the Strix uralensis or Ural owl – a powerful bird with a wingspan of more than a meter. Zink is attempting to reintroduce the species to Austria after an absence of more than 50 years. Since they have no natural predators, these owls display little fear of man, and so became easy pickings for Austria’s hunters of an earlier era. Today’s more environmentally conscious hunters, however, generally no longer pose such a threat.

As we crunch through the snow past a large enclosure of red deer, Zink explains that 22 owls were released last year – 13 in the Vienna Woods, and nine in the wilderness area in south-western Lower Austria. He hopes to establish a self-sustaining population that will form a stepping-stone between natural populations in Slovenia and the Bohemian Forest on the German-Czech Republic border.

Since the nearest release site is some 35 kilometers to our west, Zink doesn’t expect to spot any Ural owls here just yet. Instead, he attempts to attract some tawny owls – a smaller and more ubiquitous relative. He whistles long, undulating hoots that carry in the snow-shrouded silence, and is answered by the shrill, metallic alarm calls of great tits and other small birds. Along with mice, beetles and earthworms, these birds – as they roost or incubate eggs at night – make up a tawny owl’s diet.

In contrast to the tawny owl, which thrives in a range of habitats, the Ural owl is more choosey. It requires much larger nest sites, making ancient woodland such as this – all hollow trees and dead wood – vital to its survival. One of the reasons that Zink is so confident that the reintroduction will succeed is that more than 30 sites have been designated ‘core zones’ – areas within the Vienna Woods in which the forest is protected and not managed or harvested.

As we enter a taller, paler, more elegant forest of beech – the dominant tree species of the Vienna Woods – we hear the thin but insistent "sree, sree, sree" of the tree creeper and look up to see it spiralling around a nearby trunk. As we listen again, the silence appears to reverberate about us. "Can you hear that?" asks Zink. It’s not the call of an owl, but the rolling, melancholic voice of the black woodpecker echoing from somewhere deep inside the wood.

Although this is the largest of the woodpeckers, measuring more than 40cm, it should be on its guard in the months and years ahead. As well as mice, rats and the occasional squirrel, it features – albeit infrequently – on the Ural owl’s menu.

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