Assessing uncertainty in coastal marsh core sampling for waterfowl foods

Quantifying foraging resources available to waterfowl in different habitat types is important for estimating energetic carrying capacity. To accomplish this, most studies collect soil-core samples from the marsh substrate, sieve and sort food items, and extrapolate energy values to wetland or landscape scales. This is a costly and time-intensive process; furthermore, extrapolation methods yield energy estimates with large variances relative to the mean. From both research and management perspectives, it is important to understand sources of this variation and estimate the number of soil cores needed to reduce the variance to desired levels. Using 2,341 cores collected from freshwater and salt marsh habitats at four sites along the Atlantic Coast, we examined sampling variation and biological variation among sites and habitats. When we removed extreme outliers in the data caused by large animal food items found in a small core sample, estimates of energy density decreased by an order of magnitude for most habitats. After removing outliers, we found inconsistent geographical variation among habitat types that was especially pronounced in freshwater and no evidence for within-season temporal depletion of food resources for any site or habitat. We used a Monte Carlo simulation approach to estimate the optimal number of cores (minimizing both cost and estimated variance) sampled in each habitat type. Across most contexts, a reduction in the coefficient of variation reached diminishing returns near 40 core samples. We recommend that researchers explicitly address outliers in the data and managers acknowledge the imprecision that can arise from including or excluding outliers when estimating energy density at landscape scales. Our results suggest that collecting 40–50 cores per habitat type was sufficient to reduce the variance to acceptable levels while minimizing overall sampling costs

Human-wildlife interactions in urban areas: a review of conflicts, benefits and opportunities

Wildlife has existed in urban areas since records began. However, the discipline of urban ecology is relatively new and one that is undergoing rapid growth. All wildlife in urban areas will interact with humans to some degree. With rates of urbanisation increasing globally, there is a pressing need to understand the type and nature of human-wildlife interactions within urban environments, to help manage, mitigate or even promote these interactions. Much research attention has focussed on the core topic of human-wildlife conflict. This inherent bias in the literature is probably driven by the ease with which can be quantified and assessed. Human-wildlife conflicts in terms of disease transmission, physical attack and property damage are important topics to understand, but conversely the benefits of human interactions with wildlife are equally important, becoming increasingly recognised although harder to quantify and generalise. Wildlife may contribute to the provision of ecosystem services in urban areas, and some recent work has shown how interactions with wildlife can provide a range of benefits to health and wellbeing. More research is needed to improve understanding in this area, requiring wildlife biologists to work with other disciplines including economics, public health, sociology, ethics, psychology and planning. There will always be a need to control wildlife populations in certain urban situations to reduce human-wildlife conflict. However, in an increasingly urbanised and resource-constrained world, we need to learn how to manage the risks from wildlife in new ways, and to understand how to maximise the diverse benefits that living with wildlife can bring

Population dynamics of mallards breeding in eastern Washington

Variation in regional population trends for mallards breeding in the western United States indicates that additional research into factors that influence demographics could contribute to management and understanding the population demographics of mallards across North America. We estimated breeding incidence and adult female, nest, and brood survival in eastern Washington in 2006 and 2007 by monitoring female mallards with radio telemetry and tested how those parameters were influenced by study year (2006 vs. 2007), landscape type (agricultural vs. natural), and age (second year [SY] vs. after second year [ASY]). We also investigated the effects of female body condition and capture date on breeding incidence, and nest initiation date and hatch date on nest and brood survival, respectively. We included population parameters in a stage-based demographic model and conducted a perturbation analysis to identify which vital rates were most influential on population growth rate (λ). Adult female survival was best modeled with a constant weekly survival rate (0.994, SE = 0.003). Breeding incidence differed between years and was higher for birds in better body condition. Nest survival was higher for ASY females (0.276, SE = 0.118) than SY females (0.066, SE = 0.052), and higher on publicly managed lands (0.383, SE = 0.212) than agricultural (0.114, SE = 0.058) landscapes. Brood survival was best modeled with a constant rate for the 7-week monitoring period (0.50, SE = 0.155). The single variable having the greatest influence on λ was non-breeding season survival, but the combination of parameters from the breeding grounds explained a greater percent of the variance in λ. Mallard population growth rate was most sensitive to changes in non-breeding survival, nest success, brood survival, and breeding incidence. Future management decisions should focus on activities that improve these vital rates if managers want to increase the production of mallards in eastern WashingtonKeywords: survival, Washington, Anas platyrhynchos, mallard, nest success, breeding demographicsKeywords: survival, Washington, Anas platyrhynchos, mallard, nest success, breeding demographic

Food Resources for Wintering and Spring Staging American Black Ducks

Abstract Habitat restoration and enhancement objectives for wintering waterfowl are typically derived by a bioenergetics modeling approach. This approach has been developed as a planning tool to identify the amount of foraging habitat required to meet North American Waterfowl Management Plan population objectives. Our objective was to provide the energetic supply component of the bioenergetics model at an important wintering area for American black ducks Anas rubripes in the Atlantic Flyway, the Eastern Shore of Virginia. We estimated food availability among four main wetland cover types used by overwintering American black ducks: brackish water, freshwater, mudflat, and salt marsh. Mudflat (221 ± 50 kg/ha) and salt marsh (728 ± 175 kg/ha) had the highest amounts of available invertebrate food density, and freshwater (42 ± 9 kg/ha) had the highest amounts of available seed biomass. Our results suggest that seed density found in freshwater wetlands on the Eastern Shore of Virginia is considerably lower than densities found in inland freshwater cover types used by dabbling ducks. We also found that levels of invertebrate density found in Virginia mudflat and salt marsh are considerably lower than levels on Long Island, New York, and in southern New Jersey. Lower levels of food density compared with both more inland and northern wintering areas suggest that American black ducks wintering in Virginia are more likely to be limited by forage availability than American black ducks and other dabbling ducks wintering both inland and in the northern portion of the wintering range.</jats:p

Evaluation of Resident Canada Goose Movements to Reduce the Risk of Goose-Aircraft Collisions at Suburban Airports

Resident (non-migratory) Canada goose (Branta canadensis) populations in suburban environments pose risks to human health and safety. Specifically, the relatively large size and gregarious behavior of geese combined with an overlap in aircraft flight space pose substantial risk of property damage and human fatalities from goose-aircraft collisions. We estimated home range and core use areas of resident Canada geese and evaluated goose movements to better define the risk of goose-aircraft collisions around Piedmont Triad International Airport in Greensboro, North Carolina, USA.We placed satellite transmitters on 16 of 763 neck- and leg-banded geese to identify and track individuals over an 18-month study period. The frequency of satellite-tagged goose movements peaked daily within the first 2 hours after sunrise (28.1%) and again near sunset (27.2%). All in-flight goose movements occurred \u3c64m above ground level. Geese flying at these altitudes posed a risk to aircraft in the take-off and landing phases of flight. For all in-flight movements, the number of movements per day was 0.13 during the molt (1 Jun–15 Jul), 0.42 during early post-molt 2008 (16 Jul–31 Oct), 0.36 during late post-molt (1 Nov–31 Jan), 0.58 during breeding/nesting (1 Feb–31 May), and 0.58 during the early post-molt 2009. Satellite-tagged geese traveled a mean distance ranging from 2.0 km (SE=0.3) to 4.9 km (SE=0.4) per day, depending on sex and season, which supports the need for intensive goose management within a minimum distance of 8 km from airports. Mean fixed 95% kernel home range and 50% core use area were 991.8 ha (SE=241.1) and 120.4 ha (SE=24.6), respectively. Additionally, we monitored site recolonization of nuisance geese after the controlled removal of 60 resident geese from 1 site, which eliminated 24.2% of those initially banded at the site in 2008, but other geese began to recolonize the site within 27 days. Rapid recolonization of the removal site suggests that lethal removal should be conducted at all molt locations within a minimum distance of 8 km of suburban airports and any additional removal or management resources should be applied to greater distances to prevent recolonization of these sites by geese in close proximity to the removal site. Published 2015. This article is a U.S. Government work and is in the public domain in the USA