Monitoring Low Density Avian Populations: An Example using Mountain Plovers

Declines in avian populations highlight a need for rigorous, broad-scale monitoring pro-grams to document trends in avian populations that occur in low densities across expansive landscapes. Accounting for the spatial variation and variation in detection probability inherent to monitoring programs is thought to be effort-intensive and time-consuming. We determined the feasibility of the analytical method developed by Royle and Nichols (2003), which uses presence-absence (detection-non-detection) field data, to estimate abundance of Mountain Plovers (Charadrius montanus) per sampling unit in agricultural fields, grassland, and prairie dog habitat in eastern Colorado. Field methods were easy to implement and results suggest that the analytical method provides valuable insight into population patterning among habitats. Mountain Plover abundance was highest in prairie dog habitat, slightly lower in agricultural fields, and substantially lower in grassland. These results provided valuable insight to focus future research into Mountain Plover ecology and conservation

Optimizing Wildlife Monitoirng Strategies in a Dynamic Setting (Poster)

Long term, broadly distributed datasets are ideal for effective wildlife management.  However, collecting and utilizing these data present a variety of challenges to management agencies.  Idaho Department of Fish and Game is currently trying to optimize their use of monitoring resources for mule deer (Odocoileus hemionus) throughout Idaho.  Three areas are being investigated for their potential to accomplish this goal: cost effectiveness, data utilization, and efficiency in data collection.  An analysis of the cost effectiveness of monitoring methods is currently being conducted.  This analysis varies the amount of each type of data available to the population model used to estimate abundance.  The precision, credible interval width (CRI), associated with the estimate is used as the measure of effectiveness, mean 95% CRIs range from 9278 - 9804.  This measure of precision is then combined with the cost of the collection technique to compare the cost effectiveness of different monitoring methods.  Further research will focus on a weighting scheme that weights data types by both sampling precision and reliability.  Thereby allowing managers to fully utilize all available data sources based on relative quality within the framework of the population model.  A third line of research focuses on increasing the efficiency of monitoring effort through an alternative sampling design derived from seasonal nutrition.  The previous lines of research will then be combined to solve a dynamic programming problem to determine the optimal methods for monitoring population abundance while accounting for changes in the availability of monitoring resources over space and time

Confronting the Challenge of Whale Detection from Large Vessels

As a result of a moratorium on commercial whaling, most populations of large whales are increasing across the globe. However, concurrent growth in shipping means that lethal ship-whale collisions constitute a significant threat to whale conservation efforts. This study investigates the ability of ship operators to detect and avoid whales by quantifying the predictability of whale surfacing behaviors, which are the cues used to determine whale presence. Whale avoidance is challenging because whales spend most of their time underwater and thus unavailable to be detected (the “availability process”), but must be detected at sufficiently large distances (the “detection process”) to enact an effective avoidance maneuver.  We quantified one of the main characteristics of whale behavior that governs detectability – time breaking the surface – to create a novel model of whale surfacing patterns around ships while accounting for the detection process. We then estimated the frequency with which cues go undetected (i.e. whales break the surface but ship operators are unaware of them), as well as the frequency with which whales are present but unavailable for detection (i.e. below the surface of the water). This work will enable the prediction of close ship-whale encounters given different combinations of detected and/or missed cues at varying ship speeds. It will support ship operators’ avoidance efforts by quantifying the availability and detection processes in a way that facilitates the development of whale avoidance protocols

Reproductive performance of Kittlitz\u27s Murrelet in a glaciated landscape, Icy Bay, Alaska, USA

Kittlitz\u27s Murrelet (Brachyramphus brevirostris) is a dispersed-nesting seabird endemic to Alaska and eastern Russia that may have experienced considerable population declines in some parts of its range in the past few decades. Poor reproduction has been suggested as the demographic bottleneck, yet there are no direct estimates of reproduction in a glaciated area where this species reaches its highest densities at sea during the breeding season. The lack of demographic information in glacial habitats has limited our ability to interpret population trends and to clarify whether the presence of glaciers affects reproductive performance. Between 2007 and 2012, we radio-tagged Kittlitz\u27s Murrelets to measure breeding propensity, nesting success, and fecundity in the heavily glaciated landscape of Icy Bay, Alaska, USA. Of 156 radio-tagged birds, 20% were breeders, 68% were potential breeders, and 12% were nonbreeders. Radio-tagged males (29%) were more likely to be breeders compared to females (11%). Across all years, we located 34 Kittlitz\u27s Murrelet nests, 38% of which were successful. Daily nest survival probability (± SE) was 0.979 ± 0.005, with most nests failing during incubation; if extrapolated to a 55-day period from nest initiation to fledging, the nest survival rate was 0.307 ± 0.083. Low fecundity was due largely to low breeding propensity, not low nesting success. For context, we also determined the breeding status of 14 radio-tagged Marbled Murrelets (B. marmoratus), most of which were breeders (79%) and successfully fledged young (69%). Our data demonstrated that Kittlitz\u27s Murrelets were outperformed in all facets of reproduction compared to Marbled Murrelets. Low fecundity estimates for Kittlitz\u27s Murrelet were consistent with a 10% per annum decline in Icy Bay between 2002 and 2012, suggesting that poor reproductive performance contributed to the local population decline of this species

Snowshoe hares display limited phenotypic plasticity to mismatch in seasonal camouflage

As duration of snow cover decreases owing to climate change, species undergoing seasonal colour moults can become colour mismatched with their background. The immediate adaptive solution to this mismatch is phenotypic plasticity, either in phenology of seasonal colour moults or in behaviours that reduce mismatch or its consequences. We observed nearly 200 snowshoe hares across a wide range of snow conditions and two study sites in Montana, USA, and found minimal plasticity in response to mismatch between coat colour and background. We found that moult phenology varied between study sites, likely due to differences in photoperiod and climate, but was largely fixed within study sites with only minimal plasticity to snow conditions during the spring white-to-brown moult. We also found no evidence that hares modify their behaviour in response to colour mismatch. Hiding and fleeing behaviours and resting spot preference of hares were more affected by variables related to season, site and concealment by vegetation, than by colour mismatch. We conclude that plasticity in moult phenology and behaviours in snowshoe hares is insufficient for adaptation to camouflage mismatch, suggesting that any future adaptation to climate change will require natural selection on moult phenology or behaviour

Estimating Survival Probabilities of Unmarked Dependent Young When Detection Is Imperfect

We present a capture-recapture modeling approach to the estimation of survival probability of dependent chicks when only the attending adult bird is marked. The model requires that the bird\u27s nest is found prior to hatching and that the number of eggs that hatch are counted. Subsequent data are sightings of the marked adult and a count of chicks with the adult. The model allows for imperfect detection of chicks, but the number of chicks can never exceed the number of eggs in the nest (i.e., adults cannot adopt chicks). We use data from radio-tagged adult Mountain Plovers (Charadrius montanus) and their unmarked chicks as an example. We present the model in terms of precocial bird species, but the method extends to many other taxa

Testing Assumptions of Distance Sampling on a Pelagic Seabird

Distance sampling along a line transect is used commonly for monitoring changes of birds’ abundance at sea. A critical yet rarely tested assumption of line-transect-sampling theory is that all birds along the transect line (i.e., directly in front of the boat) are detected or that probability of detecting a bird on the line can be estimated. As part of a long-term research and monitoring program for the Kittlitz’s Murrelet (Brachyramphus brevirostris), we tested the assumption of complete detection of murrelets on the water along a transect line directly in front of a moving boat. Following standard survey procedures, we approached groups of murrelets (n = 57) at sea and recorded their distance, response (diving or flying), and duration of response. Flying murrelets (n = 27) were easily detected, but diving birds (n = 30) were more difficult to detect because of the duration of their dive. The probability that a bird dove and remained underwater long enough to avoid detection was low because birds that dove more than 150 m from the boat surfaced before the boat passed whereas birds that “waited” to dive near the boat were easily detected prior to diving. The greatest probability of nondetection was for birds diving at 55 m (diving long enough for the boat to pass) but was only 0.032 ± 0.007 (P + SE). These experiments quantifying detection probability along the transect line could be applied to any species surveyed from a boat

Understanding Abundance Patterns of a Declining Seabird: Implications for Monitoring

The Kittlitz\u27s Murrelet (Brachyramphus brevirostris) is a rare, non-colonial seabird often associated with tidewater glaciers and a recent candidate for listing under the Endangered Species Act. We estimated abundance of Kittlitz\u27s Murrelets across space and time from at-sea surveys along the coast of Alaska (USA) and then used these data to develop spatial models to describe abundance patterns and identify environmental factors affecting abundance. Over a five-week period in the summer of 2005, we recorded 794 Kittlitz\u27s Murrelets, 16 Marbled Murrelets (B. marmoratus), and 70 unidentified murrelets. The overall population estimate (N, mean ± SE) during the peak period (3–9 July) was 1317 ± 294 birds, decreasing to 68 ± 37 by the last survey period (31 July–6 August). Density of Kittlitz\u27s Murrelets was highest in pelagic waters of Taan Fjord (18.6 ± 7.8 birds/km2, mean ± SE) during 10–16 July. Spatial models identified consistent “hotspots” of Kittlitz\u27s Murrelets, including several small areas where high densities of murrelets were found throughout the survey period. Of the explanatory variables that we evaluated, tidal current strength influenced murrelet abundance most consistently, with higher abundance associated with strong tidal currents. Simulations based on the empirically derived estimates of variation demonstrated that spatial variation strongly influenced power to detect trend, although power changed little across the threefold difference in the coefficient of variation on detection probability. We include recommendations for monitoring Kittlitz\u27s Murrelets (or other marine species) when there is a high degree of uncertainty about factors affecting abundance, especially spatial variability