Glen E. Bernhardt

Lasers as nonlethal avian repellents

Lasers have been demonstrated to be potentially effective avian repellents; however, studies combining adequate controls and replication that test such applications of lasers in wildlife management have not been reported. We conducted 2-choice cage tests to quantify the effectiveness of a 10-mW, continuous-wave, 633-nm laser as a visual repellent (treating a perch) against brown-headed cowbirds (Molothrus ater) and European starlings (Sturnus vulgaris), and a 68-mW, continuous-wave, 650-nm laser in dispersing (i.e., targeting birds with the laser) starlings and rock doves (Columba livia) from perches and Canada geese (Branta canadensis) and mallards (Anas platyrhynchos) from grass plots. All experiments were conducted under low ambient light (≤3 lx) conditions. In 3 experiments with stationary and moving laser beams treating a randomly selected perch, brown-headed cowbirds were not repelled. Similarly, a moving beam did not repel European starlings from treated perches or cause them to disperse when targeted. Rock doves exhibited avoidance behavior only during the first 5 min of 6 80-min dispersal periods. Notably, 6 groups of geese (4 birds/group) exhibited marked avoidance of the beam during 20-min periods (n = 23), with a mean 96% of birds dispersed from laser-treated plots. Six groups of mallards (6 birds/group) also were dispersed (x = 57%) from treated plots during 20-min periods (n = 12), but habituated to the beam after approximately 20 min. We contend that lasers will prove useful as avian repellents, but further controlled studies are needed to evaluate species-specific responses relative to laser power, beam type, wavelength, light conditions, and captive versus field scenarios.

Efficacy of Aircraft Landing Lights in Stimulating Avoidance Behavior in Birds

Abstract Aircraft collisions with wildlife (primarily birds) are costly in terms of injury or loss of human life, loss of the animals involved, damage to property and business, and the use of lethal control of wildlife at airports worldwide. One potential nonlethal technique to reduce bird–aircraft collisions—pulsed white and wavelength-specific aircraft-mounted light—has been considered for nearly 3 decades, but the efficacy of the technique has not been evaluated quantitatively. We tested the hypothesis that during daylight, captive birds exposed to an approaching ground-based vehicle exhibiting pulsing 250-W white aircraft landing lights would initiate avoidance behavior more quickly than birds experiencing an oncoming vehicle with nonpulsing (steady) or no lights (control). In experiments involving captive brown-headed cowbirds (Molothrus ater), Canada geese (Branta canadensis), European starlings (Sturnis vulgaris), herring gulls (Larus argentatus), and mourning doves (Zenaida macroura), only cow-birds exhibited a response to the landing lights, but not consistently. Specifically, cowbird groups (9 groups/treatment, 6 birds/group) responded more quickly to pulse versus control treatments, equating to a greater distance (x̄ ± SE) of the approaching vehicle from mid-cage per reacting bird (control: 35.8 ± 9.7 m, pulse: 50.5 ± 10.9 m; P = 0.015). However, in a subsequent experiment involving the exposure of cowbirds to control, pulse, and steady-light treatments, we observed no difference in response among treatment groups. Although 250-W white landing lights pulsed at 45 cycles/min influenced behavior of captive birds in response to an oncoming ground-based vehicle, the avoidance response was inconsistent across experiments with cowbirds, and we observed little or no avoidance behavior in experiments with other species. We suggest that further research is needed to investigate avian response to specific light wavelengths and pulse frequencies.

Aerial Photography Techniques to Estimate Populations of Laughing Gull Nests in Jamaica Bay, New York, 1992-1995

-We evaluated aerial photography (full coverage, using fixed-wing aircraft) and aerial video (transects, using helicopter) surveys to estimate the population of Laughing Gull (Larus atricilla) nests in Jamaica Bay, New York, duringJune 1992-1995. We counted 4,920 nests in the colony using aerial photography and estimated 5,367 nests using aerial video in 1992. In 1993-1995, we respectively counted 5,691, 5,095, and 6,126 nests in the colony using aerial photography, and estimated from ground plots that our counts differed from the actual number of nests by means of-9% to 1%. Overall (1993-1995) correction factors (by which to multiply the aerial photography nest counts) to estimate the mean and 95% lower and upper CI range of the nest population were 1.04, 0.96 and 1.13, respectively. Ninety-seven percent of nests identified using aerial photography or video had >1 adult Laughing Gull present or within 1 m of the nest. The aerial video survey was less expensive (

AGE-SPECIFIC REPRODUCTION BY FEMALE LAUGHING GULLS (LARUS ATRICILLA)

2,100 United States currency) than the aerial photography survey (

Determination of body density for twelve bird species

4,000). The estimated cost of a total count of nests from the ground is

EFFICACY OF TWO GAS CARTRIDGE FORMULATIONS IN KILLING WOODCHUCKS IN BURROWS

6,700

Response of Canada Geese to a Dead Goose Effigy

9,600. The aerial video survey provided an accurate estimate of the number of nests. Full-coverage aerial photography also provided an accurate estimate of nests in addition to habitat, nest distribution and nest density data. Received 13 June 1996, accepted 3 October 1996.

Assessing chemical control of earthworms at airports

Abstract The age at which female gulls first reproduce is poorly documented. We examined plumage and reproductive organs of Laughing Gulls (Larus atricilla) collected from May–August 2000–2001 at John F. Kennedy International Airport, New York, to determine age-specific reproductive effort. Each gull was classified as one year old (hatched in previous year), two years old, or ≥3 years old on the basis of color patterns of the hood and tail feathers and fifth primary flight feather. For females, each ovary was examined to determine if post-ovulatory follicles were present. In 2000 and 2001, the first gulls with postovulatory follicles were recorded on 15 and 18 May, respectively. Overall, 54% of the 211 two-year-old female Laughing Gulls collected during June–August showed evidence of egg laying compared to 88% of the 320 gulls ≥3 years old. None of the 50 one-year-old females examined showed evidence of egg laying. Although a lower proportion of two-year-old females laid eggs compared to older gulls, we found no difference (P ≥ 0.06) in mean number of postovulatory follicles or in frequency distribution of numbers of postovulatory follicles for the two age classes for those birds that did lay eggs. Within each sex, mean body mass increased (P < 0.05) with age. Mean left testis length of males increased (P < 0.05) with age. Our findings clearly established that two-year-old female Laughing Gulls can contribute significantly to the annual reproductive effort and that some adult (≥3 years old) females did not lay eggs.