Population Assessment of an Endangered Shorebird: the Piping Plover (Charadrius melodus melodus) in Eastern Canada

Small, at-risk populations are those for which accurate demographic information is most crucial to conservation and recovery, but also where data collection is constrained by logistical challenges and small sample sizes. Migratory animals in particular may experience a wide range of threats to survival and reproduction throughout each annual cycle, and identification of life stages most critical to persistence may be especially difficult for these populations. The endangered eastern Canadian breeding population of Piping Plover (Charadrius melodus melodus) was estimated at only 444 adults in 2005, and extensive effort has been invested in conservation activities, reproductive monitoring, and marking of individual birds, providing a comprehensive data set on population dynamics since 1998. We used these data to build a matrix projection model for two Piping Plover population segments that nest in eastern Canada in order to estimate both deterministic and stochastic rates of population growth (λd and λs, respectively). Annual population censuses suggested moderate growth in abundance between 1998–2003, but vital rate estimates indicated that this temporary growth may be replaced by declines in the long term, both in southern Nova Scotia (λd = 1.0043, λs = 0.9263) and in the Gulf of St. Lawrence (λd = 0.9651, λs = 0.8214). Nonetheless, confidence intervals on λ estimates were relatively wide, highlighting remaining uncertainty in future population trajectories. Differences in projected growth between regions appear to be driven by low estimated juvenile post-fledging survival in the Gulf, but threats to juveniles of both population segments following departure from nesting beaches remain unidentified. Similarly, λ in both population segments was particularly sensitive to changes in adult survival as expected for most migratory birds, but very little is understood about the threats to Piping Plover survival during migration and overwintering. Consequently, we suggest that future recovery efforts for these and other vulnerable migrants should quantify and manage the largely unknown sources of both adult and juvenile mortality during non-breeding seasons while maintaining current levels of nesting habitat protection.

Factors influencing awareness of community-based shorebird conservation projects in Australia

We examine the awareness of potential volunteers (n = 360) living near nine community-based shorebird conservation projects. About half of the people sampled (54%) were unaware of the nearest project. Awareness of interviewees varied substantially among projects (28-78%). Apart from gaining awareness of projects through membership of natural history groups (43%), many respondents heard of projects through friends and relatives (20%), rather than through media such as newspapers (14%) and television (2.3%). We demonstrate that community-based projects can be quantitatively and critically assessed for awareness. The use of rapid, cost-effective assessments of awareness levels has application in many conservation projects.

Shorebird Nesting Sites on the Maine Coast

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Identification of significant shorebird areas : thresholds and criteria

Aim Conservation managers designate significant areas for shorebirds based on imperfect data. Significant wetlands for migratory shorebirds have usually been identified on the basis of whether they exceed certain thresholds, defined either by total abundance (usually 20,000 waterbirds) or percentage of a population (usually 1.0%). We evaluate the performance of existing criteria and determine if lowering thresholds would improve shorebird conservation without adding unreasonable numbers of significant sites.

Location Australia.

Methods We evaluated the best available data, which is used by managers to designate significant areas, to describe the effect of lowering thresholds on the number of significant sites identified and the number of shorebirds these sites support using a range of thresholds in existing criteria. We also investigated factors which may explain interspecific differences evident when lowering thresholds.

Results When the threshold for total abundance was lowered from 20,000 to 2000 shorebirds, an additional 45 shorebird areas, holding 65% more shorebirds, were identified. When thresholds for the percentage of a population criterion were lowered from 1.0 to 0.1%, an additional 86 shorebird areas were identified which held 29% more shorebirds. The proportion of a species population counted within wetlands identified as significant by the application of criteria varied widely between species. The percentage of population criterion always identified a network of areas that included more individuals of each species than the total abundance criterion at all threshold levels tested. The percentage of species populations found in networks of significant areas showed greater increase as thresholds were lowered for species that were abundant, widespread and well represented at existing thresholds.

Main conclusions Our results suggest lowering thresholds will substantially increase the number of shorebirds in identified significant areas. However, some species will remain under-represented, partly because of interspecific differences in distribution and inadequate sampling of some shorebird habitats.

Provision of artificial shelter on beaches is associated with improved shorebird fledging success

Artificial chick shelters might improve productivity of beach-nesting birds threatened by anthropogenic disturbance. We investigated the efficacy of three different chick shelter designs against four criteria: accessibility to chicks over time, thermal insulation, conspicuousness to beach-goers, and practicality (cost and ease of transport). One design (‘A-frame’) was selected because it offered the greatest thermal insulation, was the least conspicuous, most cost effective, and performed equally well in terms of accessibility. We deployed these artificial shelters on Hooded Plover Thinornis rubricollis territories where broods were present (n 5 11), and compared the behaviour and survival rate of chicks to that at control sites (n 5 10). We were unable to discern any difference in the behaviour of broods when artificial shelters were available. However, the survival rate of chicks to fledging was 71.8% higher where an artificial shelter was provided (n 5 21 broods). This was validated by analysing data from a larger sample of broods monitored as part of an active volunteer-based management programme; shelters conferred a 42.8%increase in survival to fledging (n 5 81 broods). Thus, artificial shelters have the potential to increase survival rates of threatened shorebird chicks, though the mechanisms through which survival is increased require further investigation.

Conflict between genetic and phenotypic differentiation : the evolutionary history of a ‘lost and rediscovered’ shorebird

Understanding and resolving conflicts between phenotypic and genetic differentiation is central to evolutionary research. While phenotypically monomorphic species may exhibit deep genetic divergences, some morphologically distinct taxa lack notable genetic differentiation. Here we conduct a molecular investigation of an enigmatic shorebird with a convoluted taxonomic history, the White-faced Plover (Charadrius alexandrinus dealbatus), widely regarded as a subspecies of the Kentish Plover (C. alexandrinus). Described as distinct in 1863, its name was consistently misapplied in subsequent decades until taxonomic clarification ensued in 2008. Using a recently proposed test of species delimitation, we reconfirm the phenotypic distinctness of dealbatus. We then compare three mitochondrial and seven nuclear DNA markers among 278 samples of dealbatus and alexandrinus from across their breeding range and four other closely related plovers. We fail to find any population genetic differentiation between dealbatus and alexandrinus, whereas the other species are deeply diverged at the study loci. Kentish Plovers join a small but growing list of species for which low levels of genetic differentiation are accompanied by the presence of strong phenotypic divergence, suggesting that diagnostic phenotypic characters may be encoded by few genes that are difficult to detect. Alternatively, gene expression differences may be crucial in producing different phenotypes whereas neutral differentiation may be lagging behind.

Little Ravens 'Corvus mellori' hunt, kill and eat individuals of two species of shorebird

The Little Raven Corvus mellori is an omnivore that occasionally eats small birds. Most birds taken are thought to be eaten as carrion, though several records exist of ravens hunting and killing Budgerigars Melopsittacus undulates and a Spotted Turtle-Dove Streptopelia chinensis (Higgins et al. 2006). Both cases of bird depredation record Little Ravens attacking from above and stabbing prey to death with their beaks. Here, we report a pair of Little Ravens hunting, killing and eating a lone Sharp-tailed Sandpiper Calidris acuminita at Cheetham Wetlands, near Melbourne, Victoria (37° 53' 56"S, 144° 47' 33"E; 420 ha; see Antos et al. 2007 for a description). We also report an event which strongly implies they hunted and ate an adult Red-capped Plover Charadrius ruficapillus, and observations of hunting and eating eggs and chicks.

The bright incubate at night: sexual dichromatism and adaptive incubation division in an open-nesting shorebird

Ornamentation of parents poses a high risk for offspring because it reduces cryptic nest defence. Over a century ago, Wallace proposed that sexual dichromatism enhances crypsis of open-nesting females although subsequent studies found that dichromatism per se is not necessarily adaptive. We tested whether reduced female ornamentation in a sexually dichromatic species reduces the risk of clutch depredation and leads to adaptive parental roles in the red-capped plover Charadrius ruficapillus, a species with biparental incubation. Males had significantly brighter and redder head coloration than females. During daytime, when visually foraging predators are active, colour-matched model males incurred a higher risk of clutch depredation than females, whereas at night there was no difference in depredation risk between sexes. In turn, red-capped plovers maintained a strongly diurnal/nocturnal division of parental care during incubation, with males attending the nest largely at night when visual predators were inactive and females incubating during the day. We found support for Wallace's conclusion that reduced female ornamentation provides a selective advantage when reproductive success is threatened by visually foraging predators. We conclude that predators may alter their prey's parental care patterns and therefore may affect parental cooperation during care.

Sharing the load: role equity in the incubation of a monomorphic shorebird, the masked lapwing (Vanellus miles)

Sex roles during incubation vary dramatically in socially monogamous shorebirds. The "incubator conspicuousness" hypothesis posits that, for biparentally incubating and sexually dimorphic birds, the more conspicuous sex should incubate when visually foraging predators are inactive, and in many ecosystems this is at night. Therefore, sexually monomorphic species should share incubation equitably throughout the day and night. We examined incubation patterns in Masked Lapwings Vanellus miles and found that the contribution of the sexes to incubation was equitable. Another measure of incubation behavior, bout duration, was similar between the sexes; male bout durations were slightly shorter than for females. This finding is consistent with the predictions of the incubator conspicuousness hypothesis, although other processes may also explain equitable care.

Continental-scale decreases in shorebird populations in Australia

Decreases in shorebird populations are increasingly evident worldwide, especially in the East Asian–Australasian Flyway (EAAF). To arrest these declines, it is important to understand the scale of both the problem and the solutions. We analysed an expansive Australian citizen-science dataset, spanning the period 1973 to 2014, to explore factors related to differences in trends among shorebird populations in wetlands throughout Australia. Of seven resident Australian shorebird species, the four inland species exhibited continental decreases, whereas the three coastal species did not. Decreases in inland resident shorebirds were related to changes in availability of water at non-tidal wetlands, suggesting that degradation of wetlands in Australia’s interior is playing a role in these declines. For migratory shorebirds, the analyses revealed continental decreases in abundance in 12 of 19 species, and decreases in 17 of 19 in the southern half of Australia over the past 15 years. Many trends were strongly associated with continental gradients in latitude or longitude, suggesting some large-scale patterns in the decreases, with steeper declines often evident in southern Australia. After accounting for this effect, local variables did not explain variation in migratory shorebird trends between sites. Our results are consistent with other studies indicating that decreases in migratory shorebird populations in the EAAF are most likely being driven primarily by factors outside Australia. This reinforces the need for urgent overseas conservation actions. However, substantially heterogeneous trends within Australia, combined with declines of inland resident shorebirds indicate effective management of Australian shorebird habitat remains important.

Mangrove, Crab and Shorebird Activity as Bioindicators to the Health Status of Mangrove Ecosystems along the Surinamese Coastline, South America

This study focused on the shorebird activity along the Surinamese coast in relation to the mangrove ecosystem health. The health of three estuarine mangrove areas was assessed using important bioindicators of the mangrove ecosystem: crabs, birds and mangroves. Mangrove vegetation was measured at Weg Naar Zee, Matapica canal delta and Coronie coast. Crab activity was measured by burrow and crab counts. Occurring shorebirds were also counted at these areas. The results show that mangrove regeneration and shorebird activity is significantly related to the health of the ecosystem. Weg Naar Zee was the most damaged and highest at risk. Matapica canal delta and the Coronie coast were the least damaged, with Coronie coast showing greatest health and biodiversity of the indicators.

A chain is as strong as its weakest link: assessing the consequences of habitat loss and degradation in a long-distance migratory shorebird

The conservation of migratory species represents a major challenge, as they use multiple sites, all contributing in varying degrees in sustaining high survival and reproductive success. There is particular concern for shorebirds of the East Asian-Australasian Flyway (EAAF), where declining numbers of migratory species have mostly been attributed to habitat loss along the East Asian coast. Using a stochastic dynamic programming migration model, we assessed the effect of habitat degradation scenarios along the EAAF on migration behaviour, survival and reproductive success of a long-distance migrating shorebird, the Ruddy Turnstone (Arenaria interpres). Following manipulation of habitat quality through changes in intake rate, we found that changes on the wintering (major non-breeding) ground in South Australia had the highest negative effect on reproductive success and survival. We also identified Taiwan and the Yellow Sea as sites with high importance for reproductive success. Although habitats along the East Asian coastline are currently most threatened from a range of global change processes, we highlight the importance of conserving high-quality shorebird wintering habitat in Australia. This may be of notable importance to trans-equatorial migratory shorebirds, which often make a long non-stop flight from their wintering grounds in order to skip low-latitude sites that typically provide little food.