Bradley F. Blackwell

Foraging Locations of Double-crested Cormorants on Western Lake Erie: Site Characteristics and Spatial Associations with Prey Fish Densities

Abstract Radio-tagged double-crested cormorants ( Phalacrocorax auritus ) nesting on Middle Island, Ontario and unmarked cormorants in the western basin of Lake Erie were monitored in 1999. Radio-tagged cormorants were located by aircraft and by boat along regular survey routes. In addition, foraging flocks of radio-tagged and unmarked cormorants were located during the boat surveys. Approximately 79% of foraging radio-tagged individuals, and approximately 65% of all foraging flocks were observed within 2.5 km of shore. These percentages were greater than expected, based on the percentage of the area of water within 2.5 km of shore. All size classes of flocks examined were found more frequently than expected on water ≤10 m deep. Trawling data collected annually from 1988 to 1999 during the month of August were used to determine the historical distributions of the four fish species found to comprise the majority of the diet of cormorants in the area. August corresponded to a period when there is maximal overlap in the diets of cormorants and walleye ( Stizostedion vitreum ) in the area and when the number of foraging cormorants in the area is large. Flocks of cormorants of all size classes examined were not found proportionately more in regions that contained higher than the historical median annual catches of any of the four prey species. These results, coupled with previous bioenergetics studies, suggest that the impact of cormorants on the fishery of the western basin of Lake Erie is localized with respect to depth and distance from shore.

Repelling sandhill cranes from corn: whole-kernel experiments with captive birds

Sandhill cranes (Grus canadensis) are opportunistic omnivores that incorporate both waste and unharvested cereal grains (Gramineae) in their diets. Limited hunting of cranes to reduce crop damage has had questionable results, and lethal control of depredating species is increasingly contentious. Our objectives were to evaluate anthraquinone-based Flight ControlTM and methyl anthranilate-based ReJeX-iTTM AG-36 as nontoxic avian foraging repellents in separate 2-choice pen tests with captive greater sandhill cranes (G. c. tabida) fed with whole-kernel corn (Zea mays). In both tests, crane pairs consumed, respectively, 8.6 and 9.8 times more untreated than treated corn. Total corn consumption did not differ among the treatment and control groups during the 8-day experiment. Though both repellents were effective at deterring cranes from treated corn, neither has been tested on corn under field conditions.

Research Priorities from Animal Behaviour for Maximising Conservation Progress

Poor communication between academic researchers and wildlife managers limits conservation progress and innovation. As a result, input from overlapping fields, such as animal behaviour, is underused in conservation management despite its demonstrated utility as a conservation tool and countless papers advocating its use. Communication and collaboration across these two disciplines are unlikely to improve without clearly identified management needs and demonstrable impacts of behavioural-based conservation management. To facilitate this process, a team of wildlife managers and animal behaviour researchers conducted a research prioritisation exercise, identifying 50 key questions that have great potential to resolve critical conservation and management problems. The resulting agenda highlights the diversity and extent of advances that both fields could achieve through collaboration.

Coyote hair as an area repellent for white-tailed deer

Increasing white-tailed deer ( Odocoileus virginianus ) populations create numerous conflicts with agricultural production and transport safety. Lethal control is not always an option and area repellents, such as predator waste products, have generally shown limited effectiveness. We tested coyote ( Canis latrans ) hair as a repellent at feeding stations during the winters of 2000 and 2001 and along established deer trails during the summer of 2000 in northern Ohio. Feeding station experiments were conducted in which five treatment sites received one or three bags containing 17 g of coyote hair placed adjacent to or in front of a trough of whole kernel corn and five control sites received empty bag(s). In all feeding trials, corn consumption decreased at treated sites from 59 to 91%. Intrusions by deer at treated sites decreased by 48-96% in three tests, but did not vary in the first 3-week test when coyote hair was adjacent to the corn. Corn consumption and deer intrusions at control sites generally remained constant or showed an increase over the test period. In the deer trail test, use of trails did not differ between the pre-treatment and treatment periods for the control or treated trails. Coyote hair therefore served as an effective repellent to keep deer from a desired food source and should have use in protecting limited, discrete sites. However, coyote hair did not deter deer from moving along established trails.

Electric shock strips as bird deterrents: does experience count?

Understanding how birds detect and react to deterrent methods which are employed to protect structures is important both for the effective control of property damage, and to ensure that human health and safety are not compromised. One such device is a shock strip that causes slight pain to birds when they use a perch. Our aims were to determine: (1) the efficacy of a shock strip to flocks of Brown-headed Cowbirds (Molothrus ater), and Rock Pigeons (Columba livia); (2) the length of time to extinction of effect; (3) whether members of a flock show a behavioural response to treatment; and (4) whether the birds habituate to the treatment. When activated, shock strips were effective in displacing birds from treated areas. Birds had to experience the treatment; there was no discernible indication of flock members reacting to affected birds. When strips were deactivated after an initial period of activation, birds required more than 2 hours to return to treated areas. No habituation was observed. Because birds had to experience the shock, reduced coverage of a structure or use of sham devices to lower costs is considered inadvisable.

Reporting Difference for Colored Patagial Tags on Ring-Billed Gulls

Abstract The possible role of tag color in mediating behaviors that could bias resighting rate has not been examined. In a study that began in 2007, we marked 725 ring-billed gulls (Larus delawarensis) with Bondcote royal blue, green, yellow, or orange patagial tags. Reports we gathered over 2 years indicated approximately a 3.4∶1 bias in resighting rate toward yellow or orange tags. The observed bias is inconsistent with color-associated visibility bias or differential mortality among color-tagged breeding adults. Potential behavioral effects of tag color on individuals and conspecifics should be considered by biologists when planning marking studies.

Assessing bird avoidance of high-contrast lights using a choice test approach: implications for reducing human-induced avian mortality

Background Avian collisions with man-made objects and vehicles (e.g., buildings, cars, airplanes, power lines) have increased recently. Lights have been proposed to alert birds and minimize the chances of collisions, but it is challenging to choose lights that are tuned to the avian eye and can also lead to avoidance given the differences between human and avian vision. We propose a choice test to address this problem by first identifying wavelengths of light that would over-stimulate the retina using species-specific perceptual models and by then assessing the avoidance/attraction responses of brown-headed cowbirds to these lights during daytime using a behavioral assay. Methods We used perceptual models to estimate wavelength-specific light emitting diode (LED) lights with high chromatic contrast. The behavioral assay consisted of an arena where the bird moved in a single direction and was forced to make a choice (right/left) using a single-choice design (one side with the light on, the other with the light off) under diurnal light conditions. Results First, we identified lights with high saliency from the cowbird visual perspective: LED lights with peaks at 380 nm (ultraviolet), 470 nm (blue), 525 nm (green), 630 nm (red), and broad-spectrum (white) LED lights. Second, we found that cowbirds significantly avoided LED lights with peaks at 470 and 630 nm, but did not avoid or prefer LED lights with peaks at 380 and 525 nm or white lights. Discussion The two lights avoided had the highest chromatic contrast but relatively lower levels of achromatic contrast. Our approach can optimize limited resources to narrow down wavelengths of light with high visual saliency for a target species leading to avoidance. These lights can be used as candidates for visual deterrents to reduce collisions with man-made objects and vehicles.

Species With Greater Aerial Maneuverability Have Higher Frequency of Collisions With Aircraft: A Comparative Study

Antipredator responses may appear unsuccessful when animals are exposed to approaching vehicles, often resulting in mortality. Recent studies have addressed whether certain biological traits are associated with variation in collision risk with cars, but not with higher speed-vehicles like aircraft. Our goal was to establish the association between different species traits (i.e., body mass, eye size, brain size, wing loading, wing aspect ratio) and the frequency of bird collisions with aircraft (hereafter, bird strikes) using a comparative approach controlling for the effects of shared ancestry. We proposed directional predictions as to how each of the species traits would affect the frequency of bird strikes. Considering 39 bird species with all traits represented, the model containing wing loading had the best fit to account for the variance in bird strikes across species. In another model with 54 species exploring the fit to different polynomial models but considering only wing loading, we found that wing loading was negatively and linearly associated with the frequency of bird strikes. Counterintuitively, species with lower wing loading (hence, higher maneuverability) had a higher frequency of bird strikes. We discuss potential non-mutually exclusive explanations (e.g., high wing loading species fly faster, thus gaining some extra time to avoid the aircraft flight path; high wing loading species are hazed more intensively at airports, which could lower collisions, etc.). Ultimately, our findings uncovered that species with low wing loading get struck at a higher rate at airports, which reduces the safety risk for humans because these species tend not to cause damaging strikes, but the consequences of their potentially higher local mortality are unknown.