Gyöngybagolyvédelmi Alapítvány

Old buildings, in particular church towers, represent the principal nesting sites for barn owls in Hungary. They depend on these for nesting as their natural nest sites within the cavities of old trees have become rare as a consequence of modern farming and forestry methods.

During the 1980s and 1990s,  widespread closure of towers took place as a measure to prevent fouling by pigeons and related damage to newly installed bell-ringing electrical equipment and wooden timber structures. These closures have had a significant impact on the barn owl population of Hungary. Barn owl conservation within the country therefore focuses on the re-establishment and enhancement of church towers as nest sites. However, a range of problems exist in carrying out this work, including attitudes of churchmen and the wider public, the conservation of buildings (damage from bird droppings on re-opening and maintaining open access within towers) and cost effectiveness.

There are three principal methods of nest site management.

1) Partial re-opening of the tower

This method employs the separation of the upper section of the church tower (in which barn owls normally nest) from the lower, through the construction of a timber floor. Partial reopening prevents the fouling of the majority of the tower whilst allowing use of the entire upper tower structure for nesting and fledging activities. This is important as studies carried out by the BOF Hungary (pdf) indicate that the short term survival of owlets hatched in ‘natural’ church towers is greater than in exterior nest boxes. The owlets are able to practice flying for several weeks and do not leave the building within this period. This method also maintains adequate refuge for birds during monitoring visits.

A widespread acceptance of partial reopening among churchmen has been confirmed by survey of attitudes to differing management methods (pdf). Its suitability in practice is however limited by its high cost in comparison to other methods.

2) Complete reopening of the tower.

This method is both simple and cheap to implement. It allows full use of the tower structure for nesting barn owls and their brood. As with partial reopening it provides the opportunity for the owlets to practice flying within the confines of the tower before leaving the building and allows the refuge of birds from disturbance during monitoring visits.

The principal disadvantage of complete re-opening is that it risks subsequent occupation by pigeons with resulting fouling of the interior of the tower. Considerable resistance to this method therefore exists from churchmen and local communities, with damage to timber structures and electrical equipment through the corrosive action of droppings being likely to occur.

3) Exterior nest box installation

This method involves the placement of a nest box within a church tower with the entrance leading directly to the tower exterior. It prevents access of owls to the wider interior of the tower which can be otherwise closed off, therefore preventing access for pigeons and subsequent problems of fouling.

Research carried out by the BOF Hungary suggests that the installation of exterior nest boxes within church buildings has disadvantages over other nest site management methods. Most significantly the short term survival of fledged owlets has been shown to be lower than those hatched within the interior spaces of church towers (pdf). Practice flight prior to leaving the nest site is prohibited within the confines of the nest box which increases the risk of the owls falling on emergence. This problem appears to be compounded by the typical occurrence of churches within the centre of towns and villages. Such locations increase the vulnerability of owlets to traffic or electrocution from power cables. A further problem is the much greater level of disturbance during nest monitoring than otherwise occurs within open buildings.

Comparative evaluation

Partial opening of church towers represents the best form of nest site management provided that adequate funding is available. This method provides protection of the tower from damage whilst maintaining adequate space for natural nesting and fledging behaviour.

While complete reopening of church towers also provides excellent breeding opportunities for owls, and is the cheapest form of management to carry out, it is largely unacceptable to the churchmen and the churchgoing population. It also risks damage to culturally significant buildings. Given the reluctance of churches to accept complete opening, widely pursuing this form of management may additionally risk damaging public relations and  therefore be counterproductive to wider barn owl conservation efforts in the longer term.

Significant ecological problems are associated with installation of exterior nest boxes. Their installation represents the least satisfactory means of management where 1) the opportunity and available finance to carry out partial opening exist, or 2) where the appropriate and sensitive application of complete opening can otherwise take place. Nonetheless, the installation of exterior nest boxes in closed churches remains an effective barn owl conservation method where other management methods are not feasible.

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