Ringed Plover Charadrius Hiaticula Research Articles

Incubation behaviour of the Common Ringed Plover Charadrius hiaticula at different latitudes

In biparental Charadriinae plovers, male and female incubation duties often resemble daily routines, with males typically incubating at night and females incubating during the day. By analysing incubation behaviour in three Arctic populations of Common Ringed Plover Charadrius hiaticula, we show that these diel routines are lost in the 24-h sunlight of the Arctic. In contrast, a non-Arctic population in East Scotland exhibited significant daily routines, with males dominating incubation during the late afternoon and night, and females dominating incubation during the early morning and midday hours. These patterns suggest that clear light/dark cycles are necessary for daily incubation routines to form in the Common Ringed Plover, although further research is needed to understand the specific drivers of this behaviour.

Modelling important areas for breeding waders as a tool to target conservation and minimise conflicts with land use change

Breeding waders are high profile species of conservation concern because of their declining populations. Their future depends on the outcomes of land-use policy and local management decisions. However, the low spatial resolution of extensive data on wader occurrence is poorly suited to directing conservation initiatives or to minimising detrimental impacts arising from land-use changes such as forest expansion. We used statistical models to produce high-resolution maps of predicted wader abundance in Britain and tested whether these were sufficiently accurate to be used for decision making. Random forest regression trees were developed using Bird Atlas data modelled with a range of environmental data sets to predict the relative abundances of ten species of breeding wader across Britain at 1-km square resolution. Similar analytical frameworks could usefully be applied in other geographical areas.Correlations with Bird Atlas metrics and other independent data indicate that these predictive models worked best for Curlew Numenius arquata and Oystercatcher Haematopus ostralegus. Model performance was poorer for species with more restricted distributions and/or habitat requirements, such as Greenshank Tringa nebularia and Ringed Plover Charadrius hiaticula. The precision of model predictions was also limited by the rescaling of data to 1-km square resolution.To facilitate practical and consistent interpretation by stakeholders influencing the status of breeding waders, model outputs were categorised into five discrete strata of relative abundance. These strata were used to produce sensitivity maps (available at https://app.bto.org/wader-map/), primarily to inform high-level policy decisions. The model outputs were also used to investigate broad-scale associations of breeding wader distribution with landscapes and land uses. These show that high proportions of populations (relative to their extent) are supported by areas with comparatively low predation risk (e.g. islands and grouse moors) and also by nature reserves. At more local scales, the sensitivity maps can be used to help decide on the levels of scrutiny required to assess development proposals (e.g. for establishment of new tree planting).

Population specific annual cycles and migration strategies in a leap-frog migrant

A common migratory pattern in birds is that northerly breeding populations migrate to more southerly non-breeding sites compared to southerly breeding populations (leap-frog migration). Not only do populations experience differences in migration distances, but also different environmental conditions, which may vary spatiotemporally within their annual cycles, creating distinctive selective pressures and migratory strategies. Information about such adaptations is important to understand migratory drivers and evolution of migration patterns. We use light-level geolocators and citizen science data on regional spring arrivals to compare two populations of common ringed plover Charadrius hiaticula breeding at different latitudes. We (1) describe and characterize the annual cycles and (2) test predictions regarding speed and timing of migration. The northern breeding population (NBP) wintered in Africa and the southern (SBP) mainly in Europe. The annual cycles were shifted temporally so that the NBP was always later in all stages. The SBP spent more than twice as long time in the breeding area, but there was no difference in winter. The NBP spent more time on migration in general. Spring migration speed was lower in the SBP compared to autumn speed of both populations, and there was no difference in autumn and spring speed in the NBP. We also found a larger variation in spring arrival times across years in the SBP. This suggests that a complex interaction of population specific timing and variation of breeding onset, length of breeding season, and proximity to the breeding area shape the annual cycle and migratory strategies.Significance statementMigration distance, climate, and the resulting composition of the annual cycle are expected to influence migration strategies and timing in birds. Testing theories regarding migration behaviours are challenging, and intraspecific comparisons over the full annual cycle are still rare. Here we compare the spatiotemporal distributions of two latitudinally separated populations of common ringed plovers using light-level geolocators. We found that there was a larger long-term variation in first arrival dates and that migration speed was slower only in spring in a temperate, short-distance migratory population, compared to an Arctic, long-distance migratory population. This suggests that a complex interaction of population specific timing and variation of breeding onset, length of breeding season and proximity to the breeding area shape the annual cycle and migratory behaviours.

Regional models of the influence of human disturbance and habitat quality on the distribution of breeding territories of common ringed plover Charadrius hiaticula and Eurasian oystercatcher Haematopus ostralegus

We estimated the influence of human disturbance and environmental factors on territory establishment in common ringed plovers Charadrius hiaticula and Eurasian oystercatchers Haematopus ostralegus, to inform the conservation of these species. We examined a 212 km stretch of coastline in the United Kingdom in 2003, mapping all breeding pairs of both study species, as well as the environmental characteristics of beaches and locations of visitors on the beach, the latter measured by filming from a light aircraft. Of the 1,003 200m sections of beach surveyed, 183 contained ringed plover territories (267 breeding pairs) and 117 contained oystercatcher territories (226 breeding pairs). 38,634 human visitors to the beach were mapped from three flights. Population densities of both ringed plovers and oystercatchers were lower in locations with high visitor numbers, even when accounting for the influence of the environmental characteristics of the beach. The two bird species showed similar rates of territory establishment at very low visitor rates, but oystercatchers showed a stronger negative response when visitor rates reached higher levels. Binary logistic regression models were used to identify areas where the birds would benefit most from reductions in the number of visitors and we illustrate how this information could be used to inform management around sites otherwise favourable for territory establishment.

Waders flying with folded legs – which species, when, where and why?

Waders normally fly with their legs stretched out under the tail, with their feet pointing backwards. Whereas there are a few published records of waders flying with their legs folded forward (like a passerine), with legs and feet tucked in under the belly feathers, the causes and consequences of waders flying with folded legs are poorly understood. Through searching the literature, asking ornithologists in person and through public calls, and from searching photos on the internet, we retrieved 90 records of 17 different species where one or more individuals flew with folded legs. It was most common in Spotted Redshank Tringa erythropus (in up to 10% of all birds) and Common Redshank T. totanus, but was also observed in short-legged species such as Dunlin Calidris alpina and Common Ringed Plover Charadrius hiaticula. The behaviour was recorded in most months of the year, in different age classes, in single birds as well as in flocks, at different ambient temperatures, and in both migratory flights and local move-ments. Whereas reducing heat loss at low temperatures is a likely, but not omnipo-tent, explanation for waders flying with folded legs, aerodynamics and leg muscle fatigue may also affect how waders keep their legs in flight. (Less)

Mark Mansel Rehfisch (11 October 1960 – 8 October 2019)

Mark Mansel Rehfisch (11 October 1960 – 8 October 2019)

The migration pattern of a monogamous shorebird challenges existing hypotheses explaining the evolution of differential migration

Differential migration by sex, where one sex migrates further than the other, occurs in many bird species. How this pattern evolves is however little understood. The first aim of this study was to investigate the extent of differential migration in the common ringed plover Charadrius hiaticula, breeding in southeast Sweden, and test three main hypotheses (the social dominance, body size and arrival time hypothesis) regarding the evolution of differential migration. Geolocators were used to derive spatiotemporal data and morphometrics were collected from the studied population. Males migrated 800 km farther compared to females, were marginally larger and there was no statistical difference in spring arrival between the sexes. In contrast to other studies none of the previously proposed hypotheses could account for the observed pattern. An additional finding was that both sexes arrive up to 1.5 months before egg laying, but males initiate territorial behavior upon arrival. Based on these observations we suggest that males have a higher energetic demand, and challenges to meet those, early in the breeding season. Therefore we hypothesize that males arrive to the breeding site with residual fuel reserves accumulated at the wintering site to cover at least parts of these demands. Based on this hypothesis we present a simple model to explain the longer migration by males. The model is contingent on a trade-off between site specific fueling rates (which we assume to increase with decreasing latitude), cost of the extra migration distance and predation risk during fueling. This framework may be applicable to other cases of differential migration, especially in temperate breeding species which exhibit long pre-egg laying periods.

Reactions of shorebirds and passerines to human development in the Russian Arctic under the influence of strict conservation measures

Anthropogenic impact on nesting waders and passerine birds in the Arctic in surroundings of the industrial complex Sabetta, Yamal Peninsula, Russia was studied. A lot of factors associated with human development may affect nesting birds. The human-subsidized predation is considered to be the most significant. Anthropogenic food sources are usually present in human-transformed habitats, as well as additional dens and perch sites. This leads to a higher press of predation. In Sabetta, there are specific conditions causing artificially-limited predation and human-induced disturbance. Finding a large number of nests in close proximity to industrial infrastructure we have suggested that waders (order Charadriiformes) and passerine (order Passeriformes) birds may be tolerant to an urbanized landscape. In the studied industrial habitat, they probably do not reduce the nesting density, thanks to particular advantages of such habitats (drainability and variety of shelters). To test this hypothesis, we performed an analysis of the relationship between the nesting density of the 8 most abundant species of waders and passerines in relation to the degree of habitat transformation. Statistical analysis was carried out using the GLM module of Statsoft Statistica 10. We found a positive relation between nesting density of the Ringed Plover (Charadrius hiaticula) and Snow bunting (Plectrophenax nivalis) and the degree of transformation. Habitat transformation did not significantly affect the White wagtail (Motacilla alba) and Red-throated pipit (Anthus cervinus). The Lapland longspur (Calcarius lapponicus) showed a clear decrease of the nest density in transformed habitats. Last but not least, the Little stint (Calidris minuta), Temminck’s stint (C. temminckii) and Red-necked phalarope (Phalaropus lobatus) completely ignored only artificial habitats, whereas in partially transformed habitats, their mean nesting density was similar to undisturbed natural areas.

Breeding populations of Little Ringed Plover Charadrius dubius and Ringed Plover Charadrius hiaticula in the United Kingdom in 2007

ABSTRACTCapsule: The 2007 national survey of the UK breeding population of Little Ringed Plovers shows a further spread into Scotland and Wales since the previous survey in 1984. In contrast, there has been a significant decrease in the Ringed Plover breeding population.Aims: To provide new breeding population estimates in the UK and Great Britain for Little Ringed Plover Charadrius dubius and Ringed Plover Charadrius hiaticula in 2007 and investigate changes in breeding distribution and habitat use since 1984.Methods: Breeding population estimates were made by combining counts of pairs from ‘key sites’ (2 × 2 km tetrads known to be occupied in/since 1984) and estimates of the numbers of pairs away from these sites based on stratified sampling. Survey periods for Little Ringed Plover: 15 April to 15 July, three visits; Ringed Plover: 15 April to 30 June, two visits.Results: Population estimates, for 2007, of 1239 (95% confidence intervals: 1175–1311) pairs of Little Ringed Plover and 5291 (5106–5478) pairs of Ringed Plovers were calculated for Great Britain, with 5438 (5257–5622) pairs of Ringed Plover estimated in the UK. Counts of Ringed Plover at inland and coastal sites, covered in both 1984 and 2007, decreased by 83% and 53%, respectively. The Little Ringed Plover population has expanded in range northward and westward since 1984. Main habitats used in 2007 by Little Ringed Plover were inland gravel and sand (25.9%) and river shingle (17.8%); and, for Ringed Plover, coastal shingle and sand (38.5% and 13.7%, respectively) and machair plus associated habitats (23.8%) in the Outer Hebrides.Conclusions: Between 1984 and 2007, the Little Ringed Plover breeding population in the UK increased considerably, expanding northward and westward, with increased use of river shingle habitats. During the same period Ringed Plover breeding numbers in the UK declined considerably in both coast and inland habitats, likely to be due to human disturbance and habitat change, respectively.

Population and Subspecies Differentiation in a High Latitude Breeding Wader, the Common Ringed Plover Charadrius hiaticula

Exploring the patterns of genetic structure in the context of geographical and phenotypic variation is important to understand the evolutionary processes involved in speciation. We investigated population and subspecies differentiation in the Common Ringed Plover Charadrius hiaticula, a high latitude wader that breeds in arctic and temperate zones from northeast Canada across Eurasia to the Russian Far East. Three subspecies, hiaticula, tundrae and psammodromus, are currently widely recognised, whereas a fourth subspecies, kolymensis, has been proposed based on geographic isolation and phenotypic differences. We genotyped 173 samples from eleven Common Ringed Plover breeding sites, representing all four putative subspecies, at eight polymorphic microsatellite loci to examine the patterns of population and subspecies differentiation. Bayesian clustering identified three genetic clusters among samples, corresponding to the breeding sites of the three currently recognised subspecies. The existence of the subspecies kolymensis was not supported. We also detected the presence of a previously unknown hybridisation zone extending from Northern Scandinavia to Belarus. Differentiation of the subspecies tundrae and hiaticula most likely occurred in allopatry on the Eurasian continent during past glaciation events, followed by population expansion leading to colonisation of Iceland and Greenland. The lack of genetic differentiation within the tundrae subspecies is consistent with ongoing range expansion and high gene flow maintained through migratory behaviour. We discuss the importance of historic climate changes, migratory behaviour and mating system on shaping the observed pattern of genetic differentiation.

Transcontinental pathways and seasonal movements of an Asian migrant, the Common Ringed Plover Charadrius hiaticula tundrae

Transcontinental pathways and seasonal movements of an Asian migrant, the Common Ringed Plover Charadrius hiaticula tundrae

Continuing influences of introduced hedgehogs Erinaceus europaeus as a predator of wader (Charadrii) eggs four decades after their release on the Outer Hebrides, Scotland

Non-native predators can cause major declines or even localised extinctions in prey populations across the globe, especially on islands. The removal of non-native predators can, therefore, be a crucial conservation management tool but there can be challenges when they are viewed as charismatic in their own right. Four decades after their introduction to islands in the Outer Hebrides, Scotland, European hedgehogs Erinaceus europaeus continue to be an important nest predator for a declining population of breeding waders. Where hedgehogs were rare, clutch survival rates (assessed using nest temperature loggers) of five species of waders (dunlin Calidris alpina, lapwing Vanellus vanellus, redshank Tringa totanus, snipe Gallinago gallinago and ringed plover Charadrius hiaticula) were higher than where hedgehogs were relatively more abundant. Hedgehogs were the most frequent nest predator identified using cameras. However, factors influencing population sizes of breeding waders are complex and unlikely to be attributable to a single species of predator. The interactions between predation, land use, habitat and the changes in each deserve further attention.

Autumn Migration Strategies and Trapping Numbers in the Common Ringed PloverCharadrius hiaticulain Southern Sweden

In this study we compare autumn migration strategies in two subspecies of the Common Ringed Plover Charadrius hiaticula in the southern Baltic Sea. This species exhibits a leap-frog migration pattern, whereby northerly breeding populations (C. h. tundrae; henceforth tundrae) migrate past the whole range of the southern population (C. h. hiaticula; henceforth hiaticula). Hiaticula migrates the shortest distance and is hypothesised to minimize energy spent on migration, whereas tundrae is hypothesized to minimize time, because a longer migration imposes time constraints upon other stages of a migrant's life history, such as moult and breeding. We use biometric data collected at Ottenby Bird Observatory, southern Oland, Sweden, between 1946-2012, to test whether each subspecies demonstrates characteristics associated with either an energy- or time-minimized migration. We used the decline in wing and total-head length over the season to distinguish the subspecies. Hiaticula migrated earlier in the season (July-mid August) compared to tundrae (late July-late September). Also the relative timing of age groups between the two subspecies differed. Juvenile and adult hiaticula migrated synchronized in time, whereas tundrae had two main periods of passage for adults (earlier) and juveniles (later). The timing fits that of other studies and gives complementary information about the passage in Europe. Juvenile tundrae showed a positive trend of observed fuel loads as the season progressed, whereas the other groups did not. Daily fuelling rates within the same season were low compared to other wader species that use Ottenby as a stopover and no difference between subspecies was found. However, tundrae stopped over for a shorter time compared with hiaticula. There was no difference in average migration speed between the subspecies, although tundrae had a higher maximum speed. There was large variation in yearly numbers between age classes in the two subspecies. In hiaticula the yearly average was 8 adults and 37 juveniles. The ratio of juvenile to adult tundrae on the other hand was almost 1:1, indicating equal use of Ottenby as stop over site in autumn. No trends in observed fuel loads over the season in hiaticula are consistent with an energy minimizing migration. As for tundrae, a shorter stopover time compared to hiaticula and a positive relationship between observed fuel load and time, are consistent with time minimizing migration. However, there are many uncertainties and more studies of migratory behaviours at several sites along the migration route are needed to understand the differences in migration strategies in this species.

Variability in the area, energy and time costs of wintering waders responding to disturbance

Birds’ responses to human disturbance are interesting due to their similarities to anti‐predator behaviour, and understanding this behaviour has practical applications for conservation management by informing measures such as buffer zones to protect priority species. To understand better the costs of disturbance and whether it will impact on population size, studies should quantify time‐related responses as well as the more commonly reported flight initiation distance (FID). Using waders wintering on an estuarine area, we experimentally disturbed foraging birds on the Wash Embayment, UK, by walking towards them and recording their responses (FID, alert time, time spent in flight, time taken to resume feeding, and total feeding time lost). We present data for 10 species of conservation concern: Curlew Numenius arquata, Oystercatcher Haematopus ostralegus, Bar‐tailed Godwit Limosa lapponica, Grey Plover Pluvialis squatarola, Redshank Tringa totanus, Knot Calidris canutus, Turnstone Arenaria interpres, Ringed Plover Charadrius hiaticula, Sanderling Calidris alba and Dunlin Calidris alpina. Larger species responded more strongly, response magnitude was greater under milder environmental conditions, and responses varied over both small and large spatial scales. The energetic costs of individual responses, however, were low relative to daily requirements and disturbance events were unlikely to be frequent enough to seriously limit foraging time. We suggest, therefore, that wintering wader populations on the Wash are not currently significantly negatively impacted by human disturbance during the intertidal foraging period. This is also likely to be the case at other estuarine sites with comparable access levels, visitor patterns, invertebrate food availability and environmental conditions.

Large-Scale Monitoring of Waders on Their Boreal and Arctic Breeding Grounds in Northern Europe

Large-scale and population-wide monitoring of waders on their boreal and arctic breeding grounds has hitherto been lacking, mainly because logistics are truly challenging in regions with few ornithologists, vast areas and few roads. In Norway, Sweden and Finland (here ‘Fennoscandia’) there are now national monitoring schemes in place, aimed at tracking all bird species, which allows trends to be estimated for northern wader populations. We present joint Fennoscandian population trends for 24 wader species, covering the period 2002–2013 (in some cases somewhat shorter time periods). The data stem from 1263 routes in Norway, Finland, and the northern two thirds of Sweden, all situated north of 58°N. This area of one million km2 largely coincides with the boreal and arctic parts of Fennoscandia. The trends found are rather evenly distributed between strong increases and strong declines. Trends do not differ between short- and long-distance migrants, nor do they vary in relation to breeding latitude. Ringed Plover Charadrius hiaticula, Wood Sandpiper Tringa glareola, Green Sandpiper T. ochropus and Common Redshank T. totanus had significant positive trends, whereas Common Snipe Gallinago gallinago, Ruff Philomachus pugnax and Spotted Redshank Tringa erythropus were declining significantly in numbers. Trends could be calculated even for relatively uncommon breeding birds such as Temminck's Stint Calidris temminckii, Eurasian Dotterel Charadrius morinellus, Broad-billed Sandpiper Limicola falcinellus, Jack Snipe Lymnocryptes minimus and Red-necked Phalarope Phalaropus lobatus, although these trends build on few routes and individuals, and thus have low precision. The monitoring schemes in Norway and Finland are expected to increase in coverage in the coming years, with up to a total of 1555 northern routes being tracked when the schemes are fully developed. This should enable still more robust trend estimates for northern waders on their Fennoscandian breeding grounds to be calculated in the future.

Fugler i Norge i 2005 - Rapport fra Norsk faunakomité for fugl (NFKF)

THE NORWEGIAN BIRD REPORT 2005 - a report on locally uncommon and scarce birds in Norway in 2005, by the Norwegian Birds Records Committee (NFKF) The basis of this report is the annual reports produced by the county rarities committees. For 2005 all the counties on the mainland contributed to the report, although Finnmark, Troms, Sogn & Fjordane, Rogaland and Vest-Agder counties did not publish own county reports. Svalbard archipelago and Jan Mayen did not contribute to this report. We believe this report reflects fairly well observations from Norway in 2005. Readers should take care to note the geographical or time delimitation of the records stated for the different species, as stated in codes immediately after the scientific name of the species. The Norwegian Birds Records Committee (NFKF) has been publishing annual reports since 1991. The occurrence of Bewick’s Swan Cygnus columbianus was the poorest in NFKFs history, and the occurence of Lesser White-fronted Geese Anser erythropus at the traditional feeding and roosting site at Valdakmyra, Porsanger (FI) continued to be very low. White-fronted Geese Anser albifrons were seen in poor numbers, while Bar-headed Geese Anser indicus were seen in record high numbers. Mandarin Ducks Aix galericulata occurred in high numbers. Gadwalls Anas strepera have occurred in steadily increasing numbers in Norway in recent years, and 2005 was the best year to date for this species. Garganeys Anas qurquedula had a poor year. Quail Coturnix coturnix occurred in good numbers for the fourth year in succession. Yellow-billed Divers Gavia adamsii experienced the second best year since 1991. Due to favourable weather conditions in late August both Sooty Shearwaters Puffinus griseus and Manx Shearwaters Puffinus puffinus occurred in record high numbers. Many Rough-legged Buzzards Buteo lagopus were seen during the winter months. The Eurasian Hobby Falco subbuteo is a raptor that has occurred in high numbers in recent years, and 2005 was the third best year ever. The occurrence of Avocets Recurvirostra avosetta was very poor. Several shorebirds, such as Ringed Plover Charadrius hiaticula, Northern Lapwings Vanellus vanellus, Sanderlings Calidris alba and Bar-tailed Godwits Limosa lapponica were reported in high numbers from mid-January following the winter storm «Inga». The number of migrating Broad-billed Sandpipers Limicola falcinellus, Black-tailed Godwits Limosa limosa and Red-necked Phalaropes Phalaropus lobatus were the second best in NFKFs history. Migrating Pomarine Skuas Stercorarius pomarinus was seen in good numbers. Iceland Gulls Larus glaucoides occurred in record high numbers while the occurrence of Little Gulls Larus minutus and Glaucous Gulls Larus hyperboreus was the third best in NFKFs history. The occurrence of Black Terns Chlidonias niger was very poor. Wood Larks Lullula arborea occurred in record high numbers. The negative trend related to migrating Horned Larks Eremophila alpestris continued in 2005 and the last six years represent the six poorest years for this species. Red-throated Pipits Anthus cervinus had another poor year, while Richard’s Pipits Anthus richardi occured in record high numbers. The occurrence of Yellow Wagtails Motacilla flava flavissima was the poorest in NFKF’s history. Stonechats Saxicola torquata occurred in record high numbers and seventeen confirmed breeding pairs were recorded from coastal areas. The Mistle Thrush Turdus viscivorus is probably expanding significantly in the north of its distribution range. The number of singing Common Grasshopper Warblers Locustella naevia and the occurrence of Yellow-browed Warblers Phylloscopus inornatus was the best ever recorded. The number of Barred Warblers Sylvia nisoria was the second best in NFKF’s history. The number of Great Grey Shrikes Lanius excubitor was the highest ever recorded. Two-barred Crossbills Loxia leucoptera and Pine Grosbeaks Pinicola enucleator occurred in poor numbers. The Ortolan Bunting Emberiza hortulana still has a negative trend and is disappearing from former breeding areas. The Rustic Bunting Emberiza rustica experienced the poorest year in NFKFs history, while the occurrence of Little Buntings Emberiza pusilla was the best ever recorded.

Predicting the population consequences of human disturbance for Ringed PloversCharadrius hiaticula: a game theory approach

Human disturbance and its potential impacts upon bird populations are currently topical and contentious issues for conservationists. Although many studies have revealed a behavioural impact, or even direct effect on breeding success or survival, these cannot usually be extended to predict the impact on population size. Here we present a population model that allows predictions of the effect that changes in human numbers, visiting a 9‐km‐long section of the coastline, may have upon the size of a Ringed PloverCharadrius hiaticulapopulation. Human disturbance affects Ringed Plovers in our study area through birds avoiding areas of high disturbance and, in addition, through the accidental trampling of a small number of nests by people walking on the beach. Using the level of human disturbance and habitat variables (which define territory quality) it is possible to predict which areas of beach are occupied and therefore the sites available to the population. Breeding success, for a given area of beach, can be predicted from habitat data. Incorporating known, density‐independent, adult mortality allows the equilibrium population size to be predicted. This provides a model that predicts population size. This model is then used to predict the population that the site would support with different, hypothetical, levels of disturbance. If nest loss from human activity was prevented, for example by fencing nests, we predict the Plover population size would increase by 8%. A complete absence of human disturbance would cause a population increase of 85%. If the numbers of people were to double, we predict the population would decrease by 23%.

Different timing of autumn migration of two Ringed Plover Charadrius hiaticula subspecies through the southern Baltic revealed by biometric analysis

Ringed Plovers were trapped in Puck Bay (southern Baltic) between 1983 and 2002 during autumn migration. In adults a clear decrease of mean wing and bill lengths occurred between the third decade (ten‐day period) of July and the first decade of August. A similar pattern was observed in juvenile wing lengths, whereas a sharp decline in mean bill length occurred later, between the second and the third decade of August. These changes in biometrics suggested that the larger birds passing through the study area in July belonged to the hiaticula subspecies and late migrants (adults caught from the beginning of August and juveniles caught from the third decade of August) were of the tundrae subspecies. This was supported by comparison of mean measurements of these early and late migrants passing through Puck Bay with data from other areas where only either hiaticula or tundrae occur. These data were used to compare the biometrics of adults and juveniles of each subspecies.

Effects of an agri-environment scheme on wader populations of coastal meadows of southern Sweden

Survey data on breeding wader densities and grazing intensity on coastal meadows on the Baltic island of Öland from 1988, 1998 and 2003 were used to evaluate density and density-changes of four common and widespread wader species, lapwing Vanellus vanellus, redshank Tringa totanus, oystercatcher Haematopus ostralegus and ringed plover Charadrius hiaticula in relation to grazing intensity. Population trends over time and changes in densities in relation to changes in grazing management were evaluated. Both wader densities and the environmental variable grazing intensity demonstrated significant spatial autocorrelation, but all main results were unaffected when accounting for spatial structure in the statistical tests. Breeding densities of investigated species were positively related to grazing intensity and local changes in grazing management affected the local change in wader densities. However, average grazing intensity increased over time whereas wader numbers generally remained constant or declined. Thus, changes in grazing intensity could not explain changes in overall breeding numbers. One explanation for this is probably that grazing mainly affected distribution of birds. Some evidence of a buffer effect was found in the redshank and ringed plover, in which breeding densities declined proportionally more in non-shore than in shore habitat. This was probably due to a redistribution of birds to shore habitat. It is concluded that grazing management is essential for the occurrence of waders, but might not be sufficient to ensure long-term viability of wader populations on coastal meadows.

Boöverlevnad hos strandängshäckande vadare: den relativa betydelsen av predation och trampskador av betesdjur

Nest survival among eight wader species Charadrii in relation to densities of grazing livestock (0–2 livestock/day/ha) was investigated on Öland, southeastern Sweden in 2004. When analysing a pooled data set of 173 nests, nest survival was not related to densities of livestock. Only six nests were destroyed from trampling by livestock and the estimated trampling risk of nests was low. Another analysis of 122 nests produced significantly negative relationships between nest survival and initiation of incubation. Nests were depredated more often later in the season. Nest survival was not related to livestock density or to vegetation height at nests. Mayfield estimates of hatching success were 2–21% for four of the different wader species. The highest hatching success was found in Lapwing Vanellus vanellus (21%) and Ringed Plover Charadrius hiaticula (20%), and the lowest in Oystercatcher Haematopus ostralegus (2%), while Redshank Tringa totanus had intermediate hatching success (11%). This study indicates that, at current grazing management, predation has a higher relative impact on nest survival of waders breeding on coastal meadows compared to direct and indirect effects of grazing animals.