Motion-sensitive Cameras Research Articles

The Effects of Stream Channelization and Restoration on Mammal Species and Habitat in Riparian Corridors

We investigated differences in habitat characteristics, mammal richness, and mammal activity among three stream types: channelized, unchannelized, and restored. Riparian plant species richness was significantly higher at the unchannelized stream than at the other two streams. The Kentucky Macroinvertebrate Bioassessment Index was highest at the unchannelized stream and much lower at the restored stream than the other two streams. Small mammal activity did not differ among stream types. Richness of terrestrial mammals, as determined by motion-sensitive cameras, did not differ significantly among streams. Track plot surveys showed, however, that unchannelized and restored streams had significantly higher terrestrial mammal species richness than the channelized stream. Likewise, track transect surveys conducted in snow, showed that species richness at the unchannelized stream was significantly higher than the channelized stream. There was some indication that bat activity was affected by an interaction between month and stream type. Results suggested that channelization and restoration affect habitat characteristics, mammal richness, and mammal activity; however, restored streams have potential to recover many of the characteristics of an unchannelized stream.

WILD BIRD MORTALITY AND WEST NILE VIRUS SURVEILLANCE: BIASES ASSOCIATED WITH DETECTION, REPORTING, AND CARCASS PERSISTENCE

Surveillance targeting dead wild birds, in particular American crows (Corvus brachyrhynchos), plays a critical role in West Nile virus (WNV) surveillance in the United States. Using crow decoy surrogates, detection and reporting of crow carcasses within urban and rural environments of DeKalb County, Georgia were assessed for potential biases that might occur in the county's WNV surveillance program. In each of two replicated trials, during July and September 2003, 400 decoys were labeled with reporting instructions and distributed along randomly chosen routes throughout designated urban and rural areas within DeKalb County. Information-theoretic methods were used to compare alternative models incorporating the effects of area and trial on probabilities of detection and reporting. The model with the best empirical support included the effects of area on both detection and reporting of decoys. The proportion of decoys detected in the urban area (0.605, SE=0.024) was approximately twice that of the rural area (0.293, SE=0.023), and the proportion of decoys reported in the urban area (0.273, SE=0.023) was approximately three times that of the rural area (0.103, SE=0.028). These results suggest that human density and associated factors can substantially influence dead crow detection and reporting and, thus, the perceived distribution of WNV. In a second and separate study, the persistence and fate of American crow and house sparrow (Passer domesticus) carcasses were assessed in urban and rural environments in Athens-Clarke, Madison, and Oconee counties, Georgia. Two replicated trials using 96 carcasses of each species were conducted during July and September 2004. For a portion of the carcasses, motion sensitive cameras were used to monitor scavenging species visits. Most carcasses (82%) disappeared or were decayed by the end of the 6-day study. Carcass persistence averaged 1.6 days in rural areas and 2.1 days in urban areas. We analyzed carcass persistence rates using a known-fate model framework in program MARK. Model selection based on Akaike's Information Criteria (AIC) indicated that the best model explaining carcass persistence rates included species and number of days of exposure; however, the model including area and number of days of exposure received approximately equal support. Model-averaged carcass persistence rates were higher for urban areas and for crow carcasses. Six mammalian and one avian species were documented scavenging upon carcasses. Dead wild birds could represent potential sources of oral WNV exposure to these scavenging species. Species composition of the scavenger assemblage was similar in urban and rural areas but "scavenging pressure" was greater in rural areas.

The Effect of Supplemental Prey and Prescribed Fire on Success of Artificial Nests

Nest predation hinders recruitment of avian species and may be affected by availability of alternative prey and amount of nesting cover. Therefore, we evaluated effects of food abundance (i.e., supplemental prey) and time since prescribed fire on nest success of artificial ground nests. We monitored the fate of 759 artificial ground nests from June to July 2000. No interaction (P= 0.74) occurred between fire and supplemental prey treatments. Nest success in prey-supplemented plots (37.6%) did not differ (P= 0.70) from control plots (44.9%), and nest success in burned plots (41.8%) did not differ (P = 0.86) from nonburned plots (40.7%). Motion-sensitive cameras placed on feeders revealed that mesomammals accounted for >80% of visits to feeders, indicating that supplemental prey was detected and consumed by mesomammals. Nest predators differed as a function of food abundance, with combined avian and small-mammal predation being greater in prey-supplemented (46.5%) than in control (25.9%) plots. Nest predators also differed as a function of prescribed fire Avian predation of nests was greater in burned (13.7%) than nonburned (9.9%) plots. whereas small-mammal predation was greater in nonburned (30.9%) than in burned (15.1%) plots. Altering food and cover to manage nest success may result in compensatory predation. Further work to quantify the extent of compensatory predation is needed to fully understand trade-offs of various practices for managing nest predation.

Predation of Artificial Ground Nests at Two Types of Edges in a Forest-Dominated Landscape

Artificial ground nests were placed in medium-age or older forests adjoining (a) stands of regenerating forest (vegetation < 2 m high) where 'hard' edges were created, and (b) stands of young forest (vegetation 2-8 m high) where 'soft' edges were created. Nests were placed at three distances from the forest edge (0 m, 50 m, and 100 m). Two Northern Bobwhite Quail (Colinus virginianus) eggs were placed in each nest and monitored after 7 and 14 days of exposure between late May and mid-July, 1994. Overall nest predation was 72% after 7 days and 85% after 14 days of exposure. Predation near soft edges was significantly higher than near hard edges after both 7 and 14 days of exposure. Predation near the edges was significantly higher than away from the edges after both 7 and 14 days of exposure. Two motion-sensitive cameras were used to record the identity of predator species. Cameras documented 28 predation events during 1,728 hours of operation, caused by eight species of mammals. The predators included, in order of decreasing predation: fisher (Martes pennanti), Eastern chipmunk (Tamias striatus), red-backed vole (Clethrionomys gapperi), red squirrel (Tamiasciurus hudsonicus), deer mouse (Peromyscus maniculatus), black bear (Ursus americanus), gray squirrel (Sciurus carolinensis), and striped skunk (Mephitis mephitis). The relationship between edges, predator assemblages, and nest success is complex; more studies at the landscape level are required to better understand the effects of these factors on avian population dynamics.