Effects on Vertebrates of Riparian Woodland Management for Control of Pierce’s Disease

This study was initiated in cooperation with Professors Purcell and McBride to evaluate the effects on a variety of vertebrates of the removal of vegetation as well as planting of non-disease reservoir plants in riparian zones. Studies were initiated in 1997 with the establishment of eight plots, three on Conn Creek (open, managed, and not managed), and three on the Napa River (Ecological Reserve, managed, and not managed) in Napa County, and two (managed and not managed) on Maacama Creek in Sonoma County. Five sampling procedures are used per plot as follows: a.) Two Trailmaster bait stations once per month for 7 days, b.) 15 Sherman live traps for small mammals one night per month, c.) Three point census plots for birds once per week during the breeding season (approx. March 1, 1999 to June 15, 1999), d.) Eight nesting boxes for birds checked weekly during the breeding season and e.) Six 4-square foot reptile boards checked approximately twice per month. Data are tabulated through late fall, 1998. The bait stations showed the most common mammal to be the opossum, followed by squirrels, raccoons, rats, and foxes. Larger mammal activity was lowest in the open grassy plot, and highest in the Maacama Creek managed plot and the Ecological Reserve unmanaged plot. There were no significant differences in totals of all species between the managed and unmanaged pairs of plots. The most common mammal in the live traps was the deer mouse, Peromyscus spp. Activity was highest in the open unmanaged plot and lowest in the Ecological Reserve unmanaged plot, with no significant differences between the managed and unmanaged paired plots. 66 species of birds were identified on the study plots during the 1998 breeding census, and this survey will be repeated during the spring of 1999. Eight species of birds used the nest boxes and the highest occupancy rate was in the unmanaged area on the Napa River, followed by the managed area at Conn Creek. The Reserve area had the lowest occupancy rate. No patterns were evident in use between pairs of managed and unmanaged plots. The reptile boards were used by four species of lizards, two species of snakes, the Pacific tree frog, western toad, and a salamander. The most common organism was the western fence lizard. The highest use was in the managed plot on Conn Creek, with the other plots being similar to each other, with no significant differences in total numbers between managed and unmanaged plot pairs. The results to date are encouraging and with more data we should be able to determine if management of riparian zones has an impact on a variety of vertebrates.