Vertebrate diet of the common kestrel ( Falco tinnunculus ) and barn owl ( Tyto alba ) in rain-fed crops: implications to the pest control programs

Damage associated with rodent’s outbreaks is common in the actual intensive agriculture. In order to reduce these economic losses, the placement of nest boxes for raptors could be a useful alternative to the chemical control programs. Barn owl ( Tyto alba ) and common kestrel ( Falco tinnunculus ) are two of the most commonly used species as rodent biological controls. The increase of the density of these two raptors is able to reduce the rodent’s abundance without the huge negative impact caused by the use of chemical products in surrounding biodiversity. However, other prey species could be affected by these raptors too. In order to evaluate the different impacts of barn owl and common kestrel on non-pest species, we studied the diet in 50 paired nest boxes during 3 consecutive years, based on 1249 pellets. The proportion of small mammals considered pests for agriculture (voles and mice) consumed by barn owl (80%) and common kestrel (75.6%) were quite similar. Based on nutritional requirements, nest-box occupancy probability and productivity, we estimated a consumption of 5.24 rodents per day per common kestrel nest-box placed and of 4.95 rodents per barn owl nest-box placed. However, shrews were significantly more captured by barn owl and birds were significantly more captured by common kestrel. Our results showed that both species of raptors can be effective in controlling rodents that are harmful to agriculture, but the common kestrel seemed to be slightly more efficient and might also prey on insect taxa that could be important agricultural pests.