Conor P. McGowan

EFFECTS OF HUMAN RECREATION ON THE INCUBATION BEHAVIOR OF AMERICAN OYSTERCATCHERS

Abstract Human recreational disturbance and its effects on wildlife demographics and behavior is an increasingly important area of research. We monitored the nesting success of American Oystercatchers (Haematopus palliatus) in coastal North Carolina in 2002 and 2003. We also used video monitoring at nests to measure the response of incubating birds to human recreation. We counted the number of trips per hour made by adult birds to and from the nest, and we calculated the percent time that adults spent incubating. We asked whether human recreational activities (truck, all-terrain vehicle ;obATV;cb, and pedestrian traffic) were correlated with parental behavioral patterns. Eleven a priori models of nest survival and behavioral covariates were evaluated using Akaikes Information Criterion (AIC) to see whether incubation behavior influenced nest survival. Factors associated with birds leaving their nests (n = 548) included ATV traffic (25%), truck traffic (17%), pedestrian traffic (4%), aggression with neighboring oystercatchers or paired birds exchanging incubation duties (26%), airplane traffic (1%) and unknown factors (29%). ATV traffic was positively associated with the rate of trips to and away from the nest (β1 = 0.749, P < 0.001) and negatively correlated with percent time spent incubating (β1 = −0.037, P = 0.025). Other forms of human recreation apparently had little effect on incubation behaviors. Nest survival models incorporating the frequency of trips by adults to and from the nest, and the percentage of time adults spent incubating, were somewhat supported in the AIC analyses. A low frequency of trips to and from the nest and, counter to expectations, low percent time spent incubating were associated with higher daily nest survival rates. These data suggest that changes in incubation behavior might be one mechanism by which human recreation affects the reproductive success of American Oystercatchers.

A Comparison of American Oystercatcher Reproductive Success on Barrier Beach and River Island Habitats in Coastal North Carolina

Abstract American Oystercatcher (Haematopus palliatus) numbers along the east coast of the United States are declining in some areas and expanding in others. Researchers have suggested that movement from traditional barrier beach habitats to novel inland habitats and coastal marshes may explain some of these changes, but few studies have documented oystercatcher reproductive success in non-traditional habitats. This study compares the reproductive success of the American Oystercatcher on three river islands in the lower Cape Fear River of North Carolina with that of birds nesting on barrier island beach habitat of Cape Lookout National Seashore. There were 17.6 times more oystercatcher breeding pairs per kilometer on the river island habitat than barrier beach habitat. The Mayfield estimate of daily nest content survival was 0.97 (S.E. ± 0.0039) on river islands, significantly higher than 0.92 (S.E. ± 0.0059) on barrier islands. The primary identifiable cause of nest failure on the river islands was flooding while the main cause of nest failure on the barrier islands was mammalian predation. Fledging success was equally low at both study sites. Only 0.19 chicks fledged per pair in 2002, and 0.21 chicks fledged per pair in 2003 on the river islands and 0.14 chicks fledged per pair in 2002 and 0.20 chicks fledged per pair in 2003 on the barrier islands. Many questions are still unanswered and more research is needed to fully understand the causes of chick mortality and the functional significance of non-traditional nesting habitats for the American Oystercatcher in the eastern United States.

Evaluating a multispecies adaptive management framework: must uncertainty impede effective decision-making?

Summary 1. Application of adaptive management to complex natural resource systems requires careful evaluation to ensure that the process leads to improved decision-making. As part of that evaluation, adaptive policies can be compared with alternative nonadaptive management scenarios. Also, the value of reducing structural (ecological) uncertainty to achieving management objectives can be quantified. 2. A multispecies adaptive management framework was recently adopted by the Atlantic States Marine Fisheries Commission for sustainable harvest of Delaware Bay horseshoe crabs Limulus polyphemus, while maintaining adequate stopover habitat for migrating red knots Calidris canutus rufa, the focal shorebird species. The predictive model set encompassed the structural uncertainty in the relationships between horseshoe crab spawning, red knot weight gain and red knot vital rates. Stochastic dynamic programming was used to generate a statedependent strategy for harvest decisions given that uncertainty. In this paper, we employed a management strategy evaluation approach to evaluate the performance of this adaptive management framework. Active adaptive management was used by including model weights as state variables in the optimization and reducing structural uncertainty by model weight updating. 3. We found that the value of information for reducing structural uncertainty is expected to be low, because the uncertainty does not appear to impede effective management. Harvest policy responded to abundance levels of both species regardless of uncertainty in the specific relationship that generated those abundances. Thus, the expected horseshoe crab harvest and red knot abundance were similar when the population generating model was uncertain or known, and harvest policy was robust to structural uncertainty as specified. 4. Synthesis and applications. The combination of management strategy evaluation with state-dependent strategies from stochastic dynamic programming was an informative approach to evaluate adaptive management performance and value of learning. Although natural resource decisions are characterized by uncertainty, not all uncertainty will cause decisions to be altered substantially, as we found in this case. It is important to incorporate uncertainty into the decision framing and evaluate the effect of reducing that uncertainty on achieving the desired outcomes.

Developing Objectives with Multiple Stakeholders: Adaptive Management of Horseshoe Crabs and Red Knots in the Delaware Bay

Structured decision making (SDM) is an increasingly utilized approach and set of tools for addressing complex decisions in environmental management. SDM is a value-focused thinking approach that places paramount importance on first establishing clear management objectives that reflect core values of stakeholders. To be useful for management, objectives must be transparently stated in unambiguous and measurable terms. We used these concepts to develop consensus objectives for the multiple stakeholders of horseshoe crab harvest in Delaware Bay. Participating stakeholders first agreed on a qualitative statement of fundamental objectives, and then worked to convert those objectives to specific and measurable quantities, so that management decisions could be assessed. We used a constraint-based approach where the conservation objectives for Red Knots, a species of migratory shorebird that relies on horseshoe crab eggs as a food resource during migration, constrained the utility of crab harvest. Developing utility functions to effectively reflect the management objectives allowed us to incorporate stakeholder risk aversion even though different stakeholder groups were averse to different or competing risks. While measurable objectives and quantitative utility functions seem scientific, developing these objectives was fundamentally driven by the values of the participating stakeholders.

Arguments for Using Population Models in Incidental Take Assessments for Endangered Species

Abstract Population models can be useful tools for evaluating management strategies and risks for a given species. A major, but often overlooked, component of endangered or threatened species management and recovery is the incidental take allowance of many endangered species laws. In the United States population models are seldom applied to address specific incidental take scenarios. We believe it is prudent for wildlife management agencies like the U.S. Fish and Wildlife Service to embrace explicit predictive tools to assess the possible effects of incidental take actions and to set standards for what constitutes unacceptable levels of incidental take in terms of predicted effect on population viability, recovery, and extinction. We briefly give recommendations for incorporating simulation models into jeopardy evaluations in ways that would dovetail with legislative language and provide a simple example model. Using explicit predictive models to support jeopardy determinations and incidental take decisio...

Effects of Culling on Bison Demographics in Wind Cave National Park, South Dakota

Abstract We used a stochastic Leslie matrix model parameterized with demographic data from Wind Cave National Park to evaluate effects of four culling strategies on population growth rates and age and sex structure of bison (Bison bison Linnaeus). The four culling scenarios we modeled included removal of: (1) yearlings only; (2) calf/cow combination; (3) a herd-wide proportional cull (i.e., individuals taken in proportion to their availability); and (4) calves only. We also allowed either one, two, or three years to elapse between culls to mimic current management activities, and chose culling values for each scenario that would maintain a stable population (i.e., λ ≈ 1.00). In the absence of culling, our model projected a growth rate of 16% per year (λ= 1.16) (SD = 0.02) for the Wind Cave bison population. The modeled population was characterized by a unimodal age structure for bulls and cows and a 1:1 bull: cow ratio. Removal of 75% of the yearlings or 75% of the calves every year was needed to maintain abundance at current size. These culling strategies altered the age distribution from baseline conditions, resulting in nearly equal proportions of age classes 2–15. When yearling culling or calf removal was skipped one year or two consecutive years, the yearling or calf removal option resulted in positive population growth even in the presence of a 90% cull. Because these strategies nearly removed entire cohorts, corresponding gaps were introduced in the age structure. About 40% of calves and 20% of cows needed to be removed under the annual calf/cow cull to stabilize population growth, producing a unimodal age structure of cows. However, the proportion of bulls in the 2–16 age classes increased, and the proportion of males was nearly equal across the middle age classes. The proportional cull, regardless of time between culling operations, resulted in the most symmetric age structure for males and females. To achieve λ ≈ 1.00 under a proportional cull strategy, 16% of all animals would need to be removed annually, 33% every other year, or 50% once every three years. Sensitivity and elasticity analysis indicated that adult females (5–13 years old) were the most important group of bison affectingλ. These modeled effects, along with factors such as logistical constraints, costs, efficacy, viewing opportunities for tourists, genetics, behavior, and agency policies should be considered when managers choose among culling strategies. When considering historical predation and harvest by Native Americans, we hypothesize that the calf/cow combination cull would have most closely approximated natural bison demographics after the widespread availability of horses (Equus spp.) in the year 1735. Before 1735, we hypothesize that the proportional cull would most closely represent historic conditions, although even this option might not reproduce the variability inherent in historical bison dynamics. We discuss the possibility and management implications of variable culling that might more closely mimic historical influences on bison populations on the Northern Great Plains.

A method for trapping breeding adult American Oystercatchers

Abstract We present an efficient and effective method for trapping adult, breeding American Oystercatchers (Haematopus palliatus) that minimizes disturbance to nesting birds and the risk of trapping injuries. We used a remote controlled mechanical decoy to lure territorial adults to a leg-hold noose-mat trap. We trapped 25 birds over two seasons and were successful on 54% of our trapping attempts in 2003. We only trapped birds before the breeding season or between nesting attempts to reduce nest-site disturbance.

RESIGHTINGS OF MARKED AMERICAN OYSTERCATCHERS BANDED AS CHICKS

Abstract Since 2000, we have been banding American Oystercatcher (Haematopus palliatus) chicks at Cape Lookout and Cape Hatteras national seashores as part of a long-term demographic study. Between 2000 and 2002, we banded 23 chicks. We report on resightings of eight chicks that returned to the Outer Banks of North Carolina in the summers of 2003 and 2004. These are the first records of American Oystercatcher chicks resighted near their natal areas in their 2nd and 3rd years. The 3-year-old birds appeared to be paired and acted territorial, whereas the 2nd-year birds were observed alone or in groups and did not exhibit territorial behavior. Our observations suggest that the American Oystercatchers life history is similar to that of the Eurasian Oystercatcher (Haematopus ostralegus).

A Structured approach to incidental take decision making

Decision making related to incidental take of endangered species under U.S. law lends itself well to a structured decision making approach. Incidental take is the permitted killing, harming, or harassing of a protected species under the law as long as that harm is incidental to an otherwise lawful activity and does not “reduce appreciably the probability of survival and recovery in the wild.” There has been inconsistency in the process used for determining incidental take allowances across species and across time for the same species, and structured decision making has been proposed to improve decision making. I use an example decision analysis to demonstrate the process and its applicability to incidental take decisions, even under significant demographic uncertainty and multiple, competing objectives. I define the example problem, present an objectives statement and a value function, use a simulation model to assess the consequences of a set of management actions, and evaluate the tradeoffs among the different actions. The approach results in transparent and repeatable decisions.

Piping Plovers Nesting Amongst Cottonwood Saplings

Abstract Piping Plovers (Charadrius melodus) typically nest on unvegetated sand or gravel substrates throughout their breeding range. We report on the atypical habitat characteristics of four Piping Plover nests that we found amongst young cottonwood (Populus deltoides) saplings on a sandbar island in the Missouri River along the South Dakota-Nebraska border. Atypical habitat use could have implications for estimating demographic parameters and management of this protected species. It is important to explore the extent to which Piping Plovers use atypical breeding habitat throughout their range and the quality of this potentially poor habitat.