The Hungry Owl Project - Rodenticides

Photo by Thomas Sorenson, Novato Advance

Projects & Partners

Research

Putting up owl boxes is great, but it's not enough to just put them up and hope they are used. We think there are important questions that should be asked & answered. Such as:

How successful are the Hungry Owl boxes and do the owls prefer any certain design?
What percentage of our boxes are occupied?
What, if anything, do the occupied boxes have in common, e.g., height of box, habitat, proximity to human activity, etc.
How long do Barn owls live in Marin County (the average age is 18 months in the wild)?
What are they eating here in Marin and do they have a prey preference?
Many Barn Owls are now nesting very near to human activity. How do they adapt to urban settings?
How far do the juveniles disperse and do they return to their place of hatching.
What causes their death?
How many die of rodenticide poisoning or other toxins?
What are other causes of death, e.g., car strikes, starvation, predators?

2003 was a great year with more than 150 owl boxes, 2 bat boxes, and 2 American Kestrel boxes going up in and around Marin. We began our research study with the help of Buzz Hull, Research Director of Golden Gate Raptor Observatory (GGRO) and Anne Ardillo, long-time GGRO volunteer, expert bander, and HOP volunteer.

We banded and took measurements and weights of dozens of baby barn owls found in our boxes, noting types of trees and surrounding habitat. The plan for 2004 is to expand the research and invite schools and colleges to participate in ongoing research projects. Already we have put up boxes at several schools in Marin, which will be part of presentations and studies for the students throughout the year.

So far in 2004, we have checked many boxes and we are finding a very high occupancy rate. We have also hacked out (to place a bird where it can come and go at will, such as an owl box, but where food is supplied to sustain it until it can hunt on its own) a number of juvenile barn owls that came in to WildCare after falling from their nests, or being forced out by tree cutting. Some of these nests were too inaccesible to feasibly return the owlets, so the owlets were placed in empty owl boxes on the property of dedicated volunteers (see the News page for more).

After training with Buzz Hull & Anne Ardillo, a team of volunteers are banding any owlets that are found when we check the boxes. A big improvement in our box checking this year is the the use of a small camera and television monitor. The camera is placed at the end of a long pole and this allows us to peek into an owl box from the below, by looking through the entrance hole, before going up and checking on the owls. The camera image is shown on the monitor at ground level. If the owls are too small, or a mother is on eggs, we retreat. Also, if a box is empty we save time by not having to set up a ladder and going through the process of climbing up only to find an empty box. Since we have a very small crew of dedicated volunteers, every minute saved helps!

We hope that by banding these owlets, we can begin to answer some of the questions outlined above. We would also like to have analysis done on owl pellets found in areas where we suspect rodent poisons are used, and on any owls that are brought to WildCare with suspected secondary poisoing caused by eating poisoned rodents. This testing is very expensive, but we feel it is important to our work. With evidence in hand, we may be able to have a greater influence on property owners and pest control operators who do not believe that their actions are harming birds of prey.

Banding owls is a lot of hard work, but it is very rewarding to find that so many of our boxes are being used. We have taken hundreds of pictures during the banding process and have created a photo gallery showing the banding procedure.

View the Banding Photo Gallery