Habitat and Bird Communities at Small Airports in the Midwestern USA

Despite a substantial amount of information available on bird and other wildlife strikes at large international airports, relatively few researchers have considered bird hazards at smaller general aviation (GA) airports and airfields. However, small airports often are located in rural areas, and the potential for wildlife strikes may be significant, especially because airworthiness standards related to bird strikes are much less stringent for GA aircraft compared to commercial aircraft. In this study, we conducted habitat assessments (onsite land-cover evaluations and Geographic Information System analyses) and seasonal bird surveys (walking transects) over a period of 1 year at 10 small airports in the state of Indiana, USA. Across all airports, the 3 most abundant habitat types were short (mowed) grass (mean = 40.2% of total airport area), soybean fields (10.3%), and corn fields (9.5%). At least 2 types of bird attractants (e.g., standing water, agricultural fields, woodlots) were present at each airport property, although most airports had 5 to 7 types. Seven species groups (American kestrel [Falco sparverius], blackbirds-starling, crows-ravens, mourning dove [Zenaida macroura], shorebirds, sparrows, and swallows) each were present at 9-10 of the airport properties during 1 or more seasons. The most numerous species group was blackbirds-starling, although the abundance of this and most other species groups varied widely across seasons and airports. Our results indicate that small airports in Indiana contain many bird attractants and harbor substantial numbers of birds hazardous to aviation. Management of wildlife hazards at small airports is especially challenging, given that many such airports have limited resources available for design and implementation of effective wildlife management programs. Future research should evaluate the suitability of alternative habitat types and agricultural crops that are cost-effective but compatible with effective management of wildlife hazards to aviation

Mammalian Hazards at Small Airports in Indiana: Impact of Perimeter Fencing

Fences are used at many airports and small airfields to exclude wildlife from entering critical areas. However, not all fences exclude hazardous mammals reliably, and effective fences can be too expensive for small airports to purchase and maintain. In this study, we evaluated fencing at 10 small airports in Indiana and documented the presence and relative abundance of wildlife within airport boundaries using remote cameras and spotlight surveys. Only 4 airports were completely fenced, and four were Odocoileus virginianus) or coyotes (Canis latrans) at nine of the airports with remote cameras and during spotlight surveys. There were fewer coyotes and white-tailed deer encountered during spotlight surveys at completely-fenced airports (&#;x = 0.40 individuals/km across 8 surveys; SE = 0.24) than were encountered at airports that were not completely fenced (x= 6.15; SE = 2.32; P = 0.032). Our study suggests that complete enclosure of airfields and regular fence maintenance is vital for effective wildlife-strike management at small airports

Temporally Adaptive Sampling: A Case Study in Rare Species Survey Design with Marbled Salamanders (<i>Ambystoma opacum</i>)

<div><p>Improving detection rates for elusive species with clumped distributions is often accomplished through adaptive sampling designs. This approach can be extended to include species with temporally variable detection probabilities. By concentrating survey effort in years when the focal species are most abundant or visible, overall detection rates can be improved. This requires either long-term monitoring at a few locations where the species are known to occur or models capable of predicting population trends using climatic and demographic data. For marbled salamanders (<i>Ambystoma opacum</i>) in Massachusetts, we demonstrate that annual variation in detection probability of larvae is regionally correlated. In our data, the difference in survey success between years was far more important than the difference among the three survey methods we employed: diurnal surveys, nocturnal surveys, and dipnet surveys. Based on these data, we simulate future surveys to locate unknown populations under a temporally adaptive sampling framework. In the simulations, when pond dynamics are correlated over the focal region, the temporally adaptive design improved mean survey success by as much as 26% over a non-adaptive sampling design. Employing a temporally adaptive strategy costs very little, is simple, and has the potential to substantially improve the efficient use of scarce conservation funds.</p></div

Survival curves depicting the distribution of marbled salamander (<i>Ambystoma opacum</i>) time to detection for each category of the three variables: year, method, and date.

<p>The categories for which salamanders were detected most readily yielded the shortest surveys, and thus have survival curves that appear lower on the vertical axis.</p

Interaction plot of survival curves depicting the distribution of marbled salamander (<i>Ambystoma opacum</i>) time to detection for the each method category during three date windows.

<p>The categories for which salamanders were detected most readily yielded the shortest surveys, and thus have survival curves that appear lower on the vertical axis.</p

Number of ponds where marbled salamanders (<i>Ambystoma opacum</i>) were detected in simulated surveys over 5 years with a budget allocated for 400 total surveys.

<p>Bellwether ponds were used to decide whether to survey in a given year. In the simulations below the horizontal white line where no bellwether ponds were used, the surveys were equally divided among each of the years in the study. The correlation term describes the degree to which the annual variance in larval detectability at ponds was synchronized across the study region. For each parameterization of correlation and the number of bellwether ponds, we ran 10,000 simulations. Cell shading and the numbers represent the mean number of ponds where salamanders were detected for each parameterization, with standard deviations below in parentheses.</p

Survival curves depicting the distribution of marbled salamander (<i>Ambystoma opacum</i>) time to detection for each category of the three variables: year, method, and date.

<p>The categories for which salamanders were detected most readily yielded the shortest surveys, and thus have survival curves that appear lower on the vertical axis.</p

The distribution of successful surveys for marbled salamanders (<i>Ambysoma opacum</i>) at 32 wetlands visited 6 times each.

<p>The distribution of successful surveys for marbled salamanders (<i>Ambysoma opacum</i>) at 32 wetlands visited 6 times each.</p