Bats on Our Bridges

Just when it seems that West Nile Virus has come to our county to stay, along comes a friendly, flying mammal that loves to eat mosquitos and an Eagle Scout candidate who is building and installing bat boxes to encourage their work. Just the kind of collaboration our Chapter encourages.

The new set of boxes have been built for two bridges along San Ramon Creek in Danville, as shown above, and “will help bats whose available living options are limited as our community continues to expand,” says Michael Harris, a Boy Scout from Troop 815, who built them under the sponsorship of MDAS and Connecting People With Nature.

And it is not just humans that West Nile threatens! Brian Murphy, a MDAS volunteer, found a dead Golden Eagle at Walker Canyon which had been killed by the virus.

Bridges are the safest place to install bat housing as sick or dying bats fall harmlessly into the creek away from people and creeks are natural flyways for bats to feed on insects. Houses that can hold up to 2000 bats can be readily slipped on to lower bridge railings using brackets provided by local welder Jim Howe, and there is no need for them to be moved for structure maintenance – it was an Eagle Scout from Moraga who came up with the design.

Caltrans has a Bats and Bridges program where they seek to include bat housing in all their bridge upgrade designs. In just one such installation, there are about 850,000 bats living under the Yolo Causeway on Highway 80, as shown in the “fly-out” photo above.

Upcoming Conservation Events

Dec 14

2022 East Contra Costa Christmas Bird Count


The 23rd Annual East-County count will be held Wednesday, December 14. Again, you can participate by being part of a group in the field, or by doing a count at your property if it is within the East-County Count Circle. If you’d like to participate, please send an email to . The countdown event for this one is again virtual, at 7 PM […]

Organizer: Jerry Britten – East CBC
(925) 321-5332
Dec 17

2022 Central Contra Costa Christmas Bird Count


The 68th Annual Central Contra Costa Christmas Bird Count is scheduled for Saturday, December 17, and participants are needed! You can participate by being part of a group in the field, or by doing a count at your property if it is within the Central-County Count Circle. We have many routes to cover with varied habitats and varying degrees of walking involved, so there […]