Port of Stockton
2201 W Washington St.
Stockton, CA 95203
PH 209-946-0246
FX 464-1251

Owl Nest Boxes

From time to time, it becomes necessary to tear down old and dilapidated buildings at the Port, and occasionally these structures serve as nesting sites for barn owls.  Great care is taken not to disturb active nests, and in the summer of 2006 the Port launched its Barn Owl Nest Box Program.  The goal of the program is to enhance the barn owl population by providing suitable nesting locations. Thus far the Port has installed 15 barn owl nest boxes at various locations around the East and West Complexes to replace lost nesting sites and create new ones.  The Port has found the nest boxes to be a very effective, environmentally friendly, and cost-efficient method to control the rodent population.

As of October 2008, ten of the barn owl nest boxes have been in place for about 2 years and the results thus far have been outstanding.  During the first breeding season, which typically runs from February to May for barn owls, four of the ten nest boxes were used to rear young.  Materials remaining in the boxes, such as egg shell fragments, owl pellets, feathers, etc., suggest that anywhere from four to six owlets were reared at each successful location.  We estimate that collectively the boxes housed around 20 new owls!  If you consider that, over the course of one breeding season, two adults and five young can consume as many as 2,000 rodents, you get the picture of what an efficient method of rodent control this can be without the need for toxic bait or other environmentally unfriendly controls.  Anecdotal evidence also suggests that we are having a significant impact on the rodent population as those tasked with managing the rodent population at the Port have reported a noticeable decline since the installation of the boxes. 

2008 marked the second breeding season since the boxes were installed.  Several previously unused boxes showed signs of owl activity, and it appears that we again had a success rate of 40%.  In this case success is defined as having housed a breeding pair of owls.  Several of the unused boxes had to be relocated last year.  While we had hoped to see an increase in the success rate of the boxes, it was somewhat expected that moving the unused boxes would not immediately increase the likelihood of habitation, as it often takes time for the owls to become comfortable with a newly placed box.  After seeing firsthand the effectiveness of the nest boxes, the Port purchased and installed five more in 2008.      

For more information about barn owls please visit: http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/Barn_Owl.html