USDA National Wildlife Research Center - Staff Publications

Regional assessment on influence of landscape configuration and connectivity on range size of white-tailed deer

W. David Walter — Mon, 02 Nov 2009 11:09:40 PST

Variation in the size of home range of white-tailed deer (Odocoileus virginianus) has broad implications for managing populations, agricultural damage, and disease spread and transmission. Size of home range of deer also varies seasonally because plant phenology dictates the vegetation types that are used as foraging or resting sites. Knowledge of the landscape configuration and connectivity that contributes to variation in size of home range of deer for the region is needed to fully understand differences and similarities of deer ecology throughout the Midwest. We developed a research team from four Midwestern states to investigate how size of home range of deer in agro-forested landscapes is influenced by variations in landscape characteristics that provide essential habitat components. We found that for resident female deer, annual size of home range in Illinois (mean = 0.99 km2), Michigan (mean = 1.34 km2), Nebraska (mean = 1.20 km2), and Wisconsin (mean = 1.47 km2) did not differ across the region (F3,175 = 0.42, P = 0.737), but differences between agricultural growing and non-growing periods were apparent. Variables influencing size of home range included: distance to forests, roads, and urban development from the centroid of deer home range, and percent of crop as well as four landscape pattern indices (contrast-weighted edge density, mean nearest neighbor, area-weighted mean shape index, and patch size coefficient of variation). We also identified differences in model selection for four landscapes created hierarchically to reflect levels of landscape connectivity determined from perceived ability of deer to traverse the landscape. Connectivity of selected forested regions within agro-forested ecosystems across the Midwest plays a greater role in understanding the size of home ranges than traditional definitions of deer habitat conditions and landscape configuration.

Estimating Survival of Song Bird Carcasses In Crops and Woodlots

George M. Linz — Mon, 02 Nov 2009 11:00:13 PST

Estimates of non-target animal mortality due to the effects of agricultural pesticides may be biased by the removal of carcasses by scavengers. We placed intact songbird carcasses in ripening sunflower fields in late-summer, and in harvested corn fields and woodlots in early spring to assess carcass removal by scavengers. Removal curves differed among the three habitats (P < 0.001). One day after placement, 58% of carcasses persisted in the sunflower fields, whereas 82% and 90% remained in the corn fields and woodlots, respectively. Our results suggest that survival times for carcasses are variable and dependent on habitat and, perhaps seasonal factors. In most cases, searches for carcasses should be conducted within one day of the pesticide application.

Birds Associated with Blackbird Spring Feeding Sites in South Dakota

George M. Linz — Mon, 02 Nov 2009 10:54:48 PST

From 2 to 16 April 1993, we conducted road-side surveys of birds using harvested fields of small grains, soybeans, and wm within 8 km of two blackbird roosts in east central South Dakota. Blackbirds, waterfowl, killdeer, homed larks, ring-necked pheasants, and western meadowlarks were the most common buds recorded. The frequencies of blackbirds, non-game birds, terrestrial game birds, and waterfowl was not equally distributed within the three habitats (P = 0.U.23).

Dietary Comparisons of Adult Male Common Grackles, Red-winged Blackbirds, and Yellow-headed Blackbirds in North Central North Dakota

H. Jeffrey Homan — Mon, 02 Nov 2009 10:42:16 PST

We compared the esophageal contents of adult male common grackles (Quiscalus quiscula), red-winged blackbirds (Agelaius phoeniceus),and yellow-headed blackbirds (Xanthocephalus xanthocephalus) collected in north central North Dakota from July through October 1989. Temporal variation in the diets of all species was related to food availabilities, which were heavily influenced by crop phenology. Depending on species, mean percent dry weight of sunflower achenes during August increased 2-6 times over July. Yellow-headed blackbirds migrated from north central North Dakota by early September, but substantial numbers of common grackles and red-winged blackbirds remained until mid-October. Sunflower was an important component of red-winged blackbird and common grackle diets through October. The more varied diet of yellow-headed blackbirds, in combination with the early departure from sunflower-growing regions, makes this species less likely to cause economic impact to the sunflower producer.

American Woodock Use of a Nest Box

David L. Bergman — Mon, 02 Nov 2009 10:38:49 PST

-Lombardo et al. (1989, Condor 91 :744-747) reviewed two hypotheses for the use of nest boxes by house sparrows Passer domesticus, European starlings Sturnus vulgaris, eastern bluebirds Sialia sialis, and great tits Passer major during the nonbreeding season: (1) roosting in nest cavities may be associated with nest-cavity selection during intense competition for a limited number of usable cavities, and (2) birds use cavities during the non breeding season to decrease the rate of heat loss. We were unable to locate any prior documentation of nest box use by American woodcock (Scolopax major), therefore we report on a new behavior for the American woodcock.

REPELLENTS TO REDUCE CABLE GNAWING BY WILD NORWAY RATS

Stephen A. Shumake — Tue, 07 Jul 2009 13:59:08 PDT

Rodents gnaw communications and power cables, resulting in service interruptions, fires, and other safety concerns. Commensal rodents such as the Norway rat (Rattus norvegicus) have been implicated in many of these situations. Two chemical repellents (capsicum oleoresin+apsaicin and denatonium benzoate) at 2.0% mass/mass concentrations in a polybutene carrier (Indopol-controlw) ere evaluated for repellent efficacy compared to a plastic mesh physical barrier material (Vexa*) and the polybutene carrier (placebo) alone using groups of individually caged wild Norway rats. The materials were applied to short lengths of communications cable (RG-8U) with the repellents enclosed in electrical shrink tubing around the samples and the plastic mesh attached to the samples for 7 days of continuous rat exposure. Measures of damage taken after rat exposure included mass of cable material damaged, volume loss to gnawing, depth of gnaw penetration, width of gnawing, and a qualitative index of damage based upon visual appearance. Using a stepwise discriminant analysis, we found less damage (P < 0.05) using the volume loss measure (cc) for the capsaicin and for the denatonium groups than for the polybutane-carrier (placebo) group. Other measures of gnawing damage did not improve statistical comparisons of the repellents. For all 5 measures of damage, there was a consistent rank order pattern among the means with capsaicin < denatonium < Vexar < Indopol-control.

Urban-Suburban Prairie Dog Management: Opportunities and Challenges

Gary Witmer — Tue, 23 Jun 2009 10:57:04 PDT

The historic range of the black-tailed prairie dog has undergone dramatic declines in the last century, prompting concern about the species' long-term viability. While considered a pest by many, others believe that the species is a "keystone" element of prairie ecosystems. Urban-suburban land managers are challenged with preserving colonies of prairie dogs on public lands while dealing with many conflicting interests, social costs, and risks. We review the management plans that municipalities have designed to reduce conflicts by using public input, zoned management, and a variety of management techniques. Areas of difficulty and research needs are also discussed.

Field Evaluation of Radiotransmitters for Northern Pocket Gophers

Gary Witmer — Tue, 23 Jun 2009 10:56:58 PDT

A field study was conducted in northern Idaho from June to November 1995 to evaluate the design and functional aspects of four types of Radio-transmitters for use on northern pocket gophers (Thomomys talpoides) as well as the effects of the transmitters on behavior of the animals. Twenty-five of 46 northern pocket gophers were fitted in the field with one of three models of radio-collars (AVM, NWRC, and Holohil), nine received Wildlife Materials abdominal implant transmitters (surgery conducted off-site), and 12 without transmitters served as controls. Study animals were relocated every second to fourth day until the end of the study. Individuals not retrieved by the end of the study were captured with live traps or kill traps. Recovery of marked animals (82.6%) and transmitters (82.4%) was high. Radio-collar shedding (35.3%) was a common phenomenon, but all implants remained intact. Transmitter malfunctions were infrequent. Physical side effects of the collars were uncommon (8.8%). No adverse effects of the implants were evident. Negative behavioral effects of transmitters included reduced spatial use and extreme length of claws on the front feet. No significant differences (P = 0.23) in body mass between the control and radio-marked northern pocket gophers were noted at the end of the study. Effective life of transmitters varied significantly (P = 0.01), with the Holohil collars having the greatest longevity (mean = 87.6, S. E. = 11.72 days). Though no single transmitter emerged as a superior choice for extended field studies, the Holohil model performed the best. It had the longest effective life, and ranked a consistent second place in size (small), mass (low), ease of attachment, and signal strength.

Evaluation of a Radar-Activated, Demand-Performance Bird Hazing System

Gwen R. Stevens — Tue, 23 Jun 2009 09:53:51 PDT

We evaluated a radar-activated integrated hazing system for the protection of waterfowl at large contaminated ponds at a power plant. The hazing devices in the system included acoustic alarm calls, pyrotechnics and chemical repellents dispersed in the form of a bird tear-gas. Unlike, timed interval systems, or systems with random activation sequences, birds did not habituate to the demand-performance system tested. Over the course of a year, we documented that waterfowl were 12.5 times less likely to fly over the hazed contaminated ponds relative to a non-hazed control pond. Of the waterfowl that did fly over both ponds, the likelihood of landing on the hazed contaminated pond was 4.2 times less relative to the control. Hazing also altered the flight direction and altitude of waterfowl. Mortality during the year the hazing system was in place decreased by a factor 6.5 relative to previous years where the system was not in operation. Demand-performance integrated hazing systems show promise in protecting large areas where placement of operators is not practical for logistic, safety, or long-term cost reasons.

Nightly and Seasonal Movements of Boiga irregularis on Guam

Mark Tobin — Tue, 23 Jun 2009 09:53:45 PDT

Brown tree snakes (Boiga irregularis, BTS), inadvertently introduced to the island of Guam shortly after World War II, have had catastrophic effects on the native fauna of this U.S. territory. We used radio-telemetry to monitor daytime refugia and nightly movements of 60 BTS (30 during each of two seasonal periods) to determine the extent of nightly, weekly, and monthly movements. Eighty-three percent of subadult daytime sightings were in trees, compared to only 49% of adult daytime sightings. Most measures of movement did not vary with seasonal period, sex, or age class. BTS moved an average of 64 m (Range: 9-259 m) between successive daily refugia. Mean total cumulative distance traveled between successive locations from one afternoon to the next was 238 m during January-March and 182 m during May- July. However, over the course of each seasonal period (60-70 d), most snakes concentrated their activity within core areas. During each of the two seasonal periods, snakes were located a mean distance of only 78 m and 93 m, respectively, from their original release points 30-50 d after release. Sixty to 70 d after release, snakes were a mean distance of 92 m and 68 m, respectively, from their original release points. Snakes frequently crossed dirt roads that separated forested areas at the study site. They also utilized grassy and brushy clearings, but less than would be predicted by the occurrence of such clearings in the study area. These results suggest that under the conditions of this study, BTS would be slow to reinvade areas where snakes have been removed by trapping or other means.