CONSERVATIONISTS working in England's biggest forest are celebrating a 30-year study into tawny owls.

The three-decade study, started by the Forestry Commission in 1979, is unique in its breadth and scope.

It has helped naturalists learn how climate change has critically affected the owl population.

Birdmen have been monitoring 230 nesting boxes in the 155,000-acre Kielder Water and Forest Park, Northumberland, to meet the next generation of tawny owls.

Each box has to be visited three times, first to count and weigh the eggs, then to capture the adult owl to record its vital statistics, and finally to ring chicks.

Aberdeen University research fellow Alex Millon, who has been monitoring boxes in the northern part of the forest, said: ''This is a unique study area. We are sitting on 30 years worth of data, which is amazing.

''Because of the structure of the forest and the structure of the landscape, we are able to manage roughly all the population breeding in the forest.

''That means we know everything about all the birds - we know their histories, we know where they were born, we know when they fledged and we know how old they are.

''We have a complete data set over the whole of the owl's lifetime.

''It allows us to look in very fine detail at the changing demography of this predator according to the changes which are happening right now to the prey dynamics.

''We have good evidence for the direct effect of the climate on the population of voles, which the owls eat, and it's my job to see how this affects the owls.

''And there are some changes, that's for sure; changes in the breeding success across the years, and the viability of breeding success between the years.

''To what extent it affects the population size, for instance, and the total number of tawny owl pairs in this forest, we don't yet know.''

Tawnies are not the only owl calling the wilderness home.

Long-eared owls are also present, but in much lower numbers.

Special nests for the long-eared owls have been erected throughout the forest.

Martin Davison, who has been monitoring the owls for the Forestry Commission for nearly three decades, said: ''This is a hectic time of year but also brilliantly rewarding.

''Young tawny owls look fantastic; sleepy bundles of fluff that bring a smile to your face.

''They are relatively easy to study because they tend to stay put for most of their life.

''But long-eared owls roam much wider.

''We had eight long-eared owl nests occupied last year which produced the same number of chicks.

''They are probably the least researched owl in the country, so the work we are doing at Kielder is nationally important.''