Sacramento County, in consultation with the California Department of Fish and Game and Bat Conservation International, installed six "Maberry" style bat houses near the bridge structure to mitigate for the temporary loss of bat roosting habitat during the bridge construction period. Three of the houses were installed on private property (referred to as the Kirkham property). These are noted as bat houses #1, #2, and #3. The other three were installed on the Nature Conservancy's (TNC) Cosumnes River Preserve lands (bat houses #4, #5 and #6). Each house is capable of housing 14,000 to 16,000 bats. The houses will remain in place and will be monitored for six years. After this time and following construction of the bridge, the houses located on private property will be removed. The houses located on TNC land will remain indefinitely. The bat house locations are shown on the following pages.

In addition to the bat houses installed by the County of Sacramento, a bat house was installed by Bob Wisecarver, adjacent to the bat houses on the TNC property. Mr. Wisecarver is a private individual who installs bat houses in many locations in California. He has been actively monitoring the bats on the Franklin Bridge for several years and testing some of his bat house designs on-site. Mr. Wisecarver's bat house was monitored for bats during surveys of the bat houses on the TNC property.

Sacramento County purchased the Maberry houses from Marvin Maberry (Maberry Center) of Daingerfield, Texas. Bat Conservation International (BCI) approves of the Maberry bat houses. Attachment A includes a description of the Maberry bat homes.

The bat houses are designed to accommodate approximately 14,000 to 16,000 bats, depending on species. These artificial roosts feature a steel structure covered with wood or stucco for strength and correct alignment. The wood is exterior quality, including plywood, redwood and cedar trim. The bat homes are caulked and have three coats of exterior grade paint. Heat transfer ducts located underneath the metal roof maintain proper roosting temperatures. Air vents on each end and on the sides aid in proper ventilation. Vents are shielded to reduce light entry. Plastic mesh is attached inside the wooden frame for additional roosting options and space. The bat homes were welded to support pipes that are cemented into the ground. The houses are 15 feet off the ground to provide an adequate drop zone for the bats and to protect the houses from floodwaters. The bat houses are all located in sunny locations in open areas. The bat house installation diagram is shown on the following page.

The first 3 bat houses were installed on the Kirkham property during the summer of 1999. Installation of the first bat house began on June 21, 1999. The third house was installed in August 1999. The remaining 3 bat houses were installed on the TNC lands in October 1999. Fall monitoring of the first 3 bat houses revealed some guano on the ground, indicating use as a night roost. No bats were observed inside the bat houses.

March 2000 Activities

The bats vacated the bridge by October 1999. The plan was to caulk the crevices in the bridge before the bats returned from their migration. Unfortunately, because of high water under the bridge the caulking could not begin until March 2000.

The caulking that was used on the bridge is expanding foam (Handi Foam). Handi Foam is a moisture cure polyurethane foam that expands 2 to 3 times the size of the extruded bead. It will adhere to all surfaces except Teflon, silicone and polyethylene. It is applied just like a standard plumbing caulk from a tube with a nozzle. It dries in about 20 minutes and cures in 24 hours. The cured foam can be trimmed or sanded. As it dries, it expands to fill the joint.

The County crews began caulking the trestle bridge in March 2000 to exclude the bats from taking up residence this year. Due to late heavy rains, the caulking was applied only to 35 of the 85 northern most bents by the second week of March (water under the trestle bridge made access difficult). By mid-March, approximately 500 bats had returned to the bridge. These bats were observed in trestle bents 1 through 15 . On March 14, 2000 there were about 20 bats on bents 1, 2, and 3. Hundreds of bats were observed between bents 7-8. By this time, caulking had been completed from bent 17 to 85. The exception was between bent 62 and 66. Lost Slough flows under this area and access was not possible.

Since the bats had begun to return to the bridge, caulking was halted so that no bats would become trapped behind the closed crevices. After consultation with Dave Wyatt of Sacramento City College and Terry Roscoe of the California Department of Fish and Game, it was decided to use netting to exclude the bats that had taken up residence in the bridge.

The netting is a plastic garden type net typically used to exclude birds from fruit trees. The openings are 1/4th-inch. The bat roosting exclusion measures are shown on the following page.

On March 14, 2000 Toni Barry and Tim Hawkins (DERA) met with County crews at the bridge to instruct them in placement of nets. Netting was attached to the underside of the bridge on 3 sides with staples and wood strips. The netting comes in large rolls approximately 20 feet wide. Two long strips were cut and connected to each side of the span. The middle was overlapped and sewed together with plastic strips. The middle of the net hangs down about 4-5 feet. An opening was left open on the east side of the bridge. The opening was about 5 feet x 5 feet. The first 3 spans under Bean Ranch Road to the north were netted. The bridge to the south is cement without bat habitat.

Toni and Tim returned to the bridge that evening at dusk. The temperature was 60.5 degrees F. There were clear skies and no wind. The bats began to leave the roost by 6:30 p.m. (sunset). The bats successfully left the netted roost areas with no entanglement. We used spotlights to check for bats that may have been tangled in netting after the main population left the roost. It was observed that by 7 p.m. all bats had vacated the bridge where there was no netting installed and no bats had been trapped.

The next morning Toni and Tim returned to the bridge. There was one dead bat found in the netting in span 2. It appeared to have a broken leg. It was not tangled in the net. No bats were observed roosting in the netted areas. We used reflected light from mirrors and spotlights to determine bat presence. No bats were heard in these areas.

It appeared that the bats excluded from the netted area had moved to the middle of span 5. All other areas appeared to have the same population. No new areas other than span 5 were populated. No bats were observed in the bat houses. The County crew was instructed to continue netting to the north.

After the netting was extended north to bent 6, a field review revealed no bats in the netted areas. The total bat population looks about the same. Bat guano was spotted under bat house 3.

On March 20, 2000 Tim, Toni and Kari Lewis of the California Department of Fish and Game visited the site. The bridge is now netted to bent 16. There were no bats observed in nets. Bat guano was noted under bat house 3.

Site visits continued to occur during the day and in the evening. The netted areas remained free of bats and very little flight activity was observed in the evening. Recording thermometers from BCI were installed under the bridge and in one of the bat houses.

The plan was to close the nets during the last week of March.

On March 28, 2000 the County crews were on-site to close the nets. We received a call that there were bats in some of the netted areas. The crew was instructed to halt work immediately.

Tim and Toni went to the site that evening. A bat was noted in a closed area between bents 4 and 5. We opened the net at the east end to release the bat.

Bats were also noted on the stringers (edge of bridge on the east side). The nets are open in this area. It appears that the bats did not fly into the netted area, but went in straight up and stayed there in the crevice on the edge. The netting does not deter use of the outer edge of the bridge.

We found areas in the netted spans where bats could enter. These are very small openings on the ends of the bents, or where netting is wrapped around a post, leaving a small gap underneath. All of these areas were noted.

The next morning we met with the County crew to show them the open areas that needed to be closed. The entire bridge was surveyed for bats and guano. Bats were noted on the east stringers between bents 11 and 12. We decided to close the net behind the stringer and let the bats remain in the outside crevice throughout this season. There were approximately 120 bats in the areas void of caulking or netting. We will leave these areas open for this season.

After a survey with mirrors and lights, all of the nets were closed from bent 1 to 11.

There were 3 bats observed in bat house number 2. In the evening, there were many bats observed in flight and they could be heard in the caulked areas. We will take no action there this year since they seem to be entering and exiting without difficulty. The caulking appears to have pulled away from the bridge crevices in some areas leaving small openings that allow bats to enter. It was also noted that there are many areas that have openings where bats could take up residence that we cannot observe. These are rotten boards, ends of rails, etc. Next year we will have to carefully caulk all of these areas.

During the first week of April we learned that Mexican free-tailed bats are very opportunistic and determined about accessing their favorite roosting areas. We found 4 dead bats in the netted areas that are closed (one in each span). We also found a total of 14 live bats in closed netted areas. There were about 23 bats located on the stringers just outside the net edges. All of these areas were opened to allow the live bats to escape. That evening we returned to the site to make sure the bats were getting out without problems. We had to release one bat in an area where the netting was extended down to the ground on the bent. It appears that there are openings that are not easily visible to the human eye.

The County crew closed up all the small entrance areas that could be found. Caulking was used for the tiny corners where netting cannot be stretched tight. Netting was closed where no bats were observed.

Tim and Toni continued to visit the site in the evening. This is the only time when it can be determined that a span is bat-free. The nets were opened again if bats had taken up residence in what were believed to be "bat proofed" areas. We believe that the bats hide out on top of the beams where we cannot see them during the day. Since they become more active at night, that is when they can be detected. The month of April has turned out to be two steps forward and three steps back.

After talking with Dave Wyatt and Brian Keeley, it was determined that we should attempt to complete our bat exclusion process by May 1, 2000. Since the birth of pups can begin in the latter part of May, we are anxious to halt our "harassment" of the colony and at the same time be sure that our closed areas are really free of bats.

Although Tim and Toni carry ladders, tools, netting and lights, they are really only prepared to aid bats in their evening escape escapades, and the professional County maintenance crew would be needed to finish the job successfully. With this in mind we scheduled a night work session to close the nets after the bats had vacated for their evening feeding flight.

On April 24, 2000 Toni, Tim, Tom Barnard and 3 County Bridge Maintenance workers met at the site. Toni and Tim surveyed the entire bridge. We only noted one bat in a netted area. That netted area was still open on one side. The plan was to wait for the bat to fly out and then close the open nets. There were 4 spans that were netted that had one side open. While we were waiting for dusk we walked to the north end of the bridge to visit the big brown bats in the open areas. These bats appeared to have gone into torpor due to the recent rainy and cool weather. A few weeks prior they had been active and vocal. Now they were sluggish and silent.

As we were walking back toward the netted area we observed hundreds of bats take flight out of the area that had been caulked. This was very surprising since we had not observed as many bats on previous evening visits and thought we had identified the few areas where bats had entered some of the caulked areas that had openings. We now believe that the bats inhabit the sides of the bridge (between the concrete deck and the wooden trestle), areas where boards are pulled out, rails - in short, any opening that they can get into. It was a little discouraging to imagine the work that we will have to do next year to totally exclude the bats from the bridge.

After dusk, we found some areas where bats had entered spans that were closed with nets. These were areas adjacent to the open areas on the outside stringers. The bats had managed to crawl between the bents into closed areas. These bats were released and all of the netted areas were closed.

Tim and Toni visited the site the next day. There were no bats trapped in the closed areas. We had closed off 16 spans with nets and most of the remaining spans with caulking.

Subsequent evening visits in early May revealed a population estimated at about 1,000 bats roosting in the Franklin Boulevard Bridge. Bat house number 2 has population of at least 1,000 bats and individuals are noted from time to time in house number 3. In June we were able to newborn pups in the bridge crevices. We could not determine the presence of pups in the bat houses. In June we were able to see over 2,000 newborn pups in the bridge crevices. We could not determine the presence of pups in the bat houses.

The caulking efforts would have been more successful if the work had been started earlier in the season before the bats began to arrive. More careful application of the caulking would have excluded bats from most of the crevices. A more detailed examination of the sides of the bridge will be necessary in the future to ensure that all potential roosting areas are filled with caulk or netted. This work should be completed prior to March 1, 2001. Regular monitoring of the bridge during the months of March and April will be necessary to identify any areas that might remain as roosting habitat. Those areas will need to be cleared of bats and sealed. Since the bats are beginning to take up residence in the bat houses this year, we are hopeful that they will begin to use the houses earlier and in greater numbers next season.

DERA staff and Transportation Division staff will continue to monitor the bridge through October when the bats begin to migrate out. The netting will be checked weekly for vandalism and integrity. To the extent possible, we will try to gauge the size of the colony that utilize the bridge this year. We will also continue to monitor the bat houses and quantify the number of bats that occupy them this year. The summer roosting season will also be spent studying different strategies that could be employed next season.

Part 2 of the Bat Protection Program will begin after the bats migrate out in the fall of 2000. The final exclusion activities will take place and the bridge will be monitored for bats while it is removed. Monitoring of the bat houses will be on going. The Part 2 report should be available in the summer of 2001.