The Concept
The construction and installation of Barn owl nest boxes (in order to support the declining natural breeding sites for the species, and to stabilize/increase the population of Barn owls) -when implemented with optimum spatial positioning-, is actually an international management strategy aiming at controlling small mammal populations in agriculture, through natural predation from the Barn owls.
The targeted and strategic installation of nest boxes in agricultural areas, creates a robust network for Barn owl activity, perching sites, and safe reproduction sites for the population of Barn owls. Through this population management, the natural predation upon pest rodents is gradually activated in the area, and pest populations are controlled effectively in the long term. The population density of pest rodents is kept at low levels, avoiding outbreaks and risks to public health and agricultural production. Gradually, the application of toxic rodenticides in agricultural areas can be replaced by the process of natural predation.
Historical background
There are outstanding international examples of the Barn Owl Project implementation, in order to control pest rodents in agriculture around the world.
The Israel case
Israel is the world leader in launching this scheme as a pilot in 1982. Since 2002 Israel has been implementing this program as a National Rodent Control Program. The program is now funded by the Ministry of Agriculture and Rural Development allocating an annual budget of approximately $2,000,000. Today, having implemented the program for 40 years, Israel counts more than 5,000 nest boxes positioned in agricultural areas of about 4,000 km2.
A typical density is 2 boxes/km2 and there are many areas with densities of 4,6,8,10 and 20 nest boxes per km2. The implementation of this strategy in Israel has led to an impressive reduction of up to 60% -70% in the use of rodenticides in agricultural areas.
Barn owl brings prey to her nestlings in a nest box - photo by Amir Ezer
Installation of 5,000 Barn owl nest boxes in Israel. Green color: confirmed reproduction, Orange color: Barn owl pairs, White color: still empty
The Cyprus case
In 2017, the Cyprus government decided to implement a similar program in cooperation with four different institutions: Birdlife Cyprus, the Department of Rural Development of the Ministry of Agriculture, Rural Development and Environment, the Directorate of Forests, and the Game and Fauna Service. An official meeting led to that decision, held by the Minister of Rural Development of Cyprus Mr. Konstantinos Kadis with a delegation from the University of Lausanne (Dr Alexandre Roulin), the University of Tel Aviv (Dr Yossi Leshem), the Ministry of Agriculture and Rural Development of Israel (Dr Yoav Motro), the environmental organization Birdlife Cyprus (Dr Martin Hellicar), and Civil Society Organization "TYTO" (Dr. Vassilios Bonzorlos). Today, in Cyprus there are more than 1,000 nest boxes for the Barn owl.
The USA case - California
The United States have recently implemented a similar program, focusing in the vineyards of California region. Barn owl population is managed for the natural regulation of pest rodents.
Mark Browning who founded the Barn Owl Box Company has supplied with more than 5,000 nest boxes to producers, which are placed in native crops of the mainland, mainly vineyards. Dense spatial positioning has been implemented in cases of severe problems with pest rodents. The dense placement in vineyards sometimes reaches up to 50 nest boxes per square kilometer.
Management of the Barn owl for pest rodent control in California vineyards of the United States. Photo by Humboldt State University Barn Owl Research Group
The Malaysia case
In Malaysia, the main pest rodents in rice crops with high population densities were Rattus Argentiventer and Rattus Tiomanicus. An analysis of Barn owl’s feeding habits in these infested areas, revealed that both harmful species accounted for 85.7% and 14.3% respectively, of Barn owl diet in the region (94.7% in total).
These observations demonstrate Barn owl’s amazing skills to adapt its hunting strategy to the most abundant pest rodents in agricultural areas, depending on each different geographical area, and led Malaysia to manage the Barn owl population through nest boxes installation.
Malaysia has recorded no more than 2% crop production damage in the agricultural areas where Barn owl nest boxes have been installed. The Malaysian Ministry of Agriculture proposes an average density of one nest box per 20ha-40ha (i.e., 3 to 5 cages/1km2).
Useful links:
The case of Kenya
Kenya deals for decades with the problem of maize crops destruction by pest rodents. Annual destruction reaches 20%-30% of the production, while in periods of rodent population outbreaks the destruction has reached 100% of the infested areas. To effectively face this challenge, two experimental areas were chosen to implement continuous monitoring of both the reproductive process of the Barn owl population and the population fluctuations of the rodent populations.
The decrease of pest rodents in the areas where nest boxes where installed, compared to the areas without presence of the Barn owl, was 25% higher, which clearly demonstrates the importance of Barn owl predation as a natural control mechanism in the population of pest small mammals.
The global dynamic of Barn owl (Tyto alba) in natural rodent control
An increasing interest in both world practices and scientific literature is being observed, in respect to natural control methods of pest small mammals in agriculture. Among the listed biological organisms that can function positively by reducing / limiting small mammal populations in agricultural areas, Barn owl is reported in 86% of published scientific articles, mentioning that its predatory effect has positive effects and is a capable natural limiting factor.
More and more countries are gradually focusing on adopting this solution. In the same context, the new European institutional texts and analyses (Green Deal, From Farm to Fork, Biodiversity Strategy 2030), indicate the need to turn to natural solutions and natural control mechanisms against pests in agriculture. Such solutions will contribute not only in reducing the use of chemicals but also in improving the ecosystem services in agriculture.
