Oystercatcher Haematopus ostralegus Winter Mortality in The Netherlands: The Effect of Severe Weather and Food Supply (original) (raw)
Related papers
2012
Events happening in one season can aff ect life-history traits at (the) subsequent season(s) by carry-over eff ects. Wintering conditions are known to aff ect breeding success, but few studies have investigated carry-over eff ects on survival. h e Eurasian oystercatcher Haematopus ostralegus is a coastal wader with sedentary populations at temperate sites and migratory populations in northern breeding grounds of Europe. We pooled continental European ringing-recovery datasets from 1975 to 2000 to estimate winter and summer survival rates of migrant and resident populations and to investigate long-term eff ects of winter habitat changes. During mild climatic periods, adults of both migratory and resident populations exhibited survival rates 2% lower in summer than in winter. Severe winters reduced survival rates (down to 25% reduction) and were often followed by a decline in survival during the following summer, via short-term carry-over eff ects. Habitat changes in the Dutch wintering grounds caused a reduction in food stocks, leading to reduced survival rates, particularly in young birds. h erefore, wintering habitat changes resulted in long-term ( Ͼ 10 years) 8.7 and 9.4% decrease in adult annual survival of migrant and resident populations respectively. Studying the impact of carry-over eff ects is crucial for understanding the life history of migratory birds and the development of conservation measures.
Waterbirds, 2012
Using mark-recapture models, apparent survival was estimated from older banding and re-sighting data (1978-1983) of American Oystercatchers (Haematopus palliatus) nesting on beaches and in salt marshes of coastal Virginia, USA. Oystercatchers nesting in salt marshes exhibited higher apparent survival (0.94 ± 0.03) than birds nesting on beaches (0.81 ± 0.06), a difference due to variation in mortality, permanent emigration, or both. Nesting on exposed barrier beaches may subject adults and young to higher risk of predation. These early estimates of adult survival for a species that is heavily monitored along the Atlantic and Gulf Coasts can be used to (1) develop demographic models to determine population stability, (2) compare with estimates of adult survival from populations that have reached carrying capacity, and (3) compare with estimates of survival from other oystercatcher populations and species.
A survey of wintering American Oystercatchers from Georgia To Virginia , U . S . A . , 1999
2008
Using a variety of survey techniques we attempted to estimate the size of the wintering population of American Oystercatchers Haematopus palliatus palliatus along the Atlantic coast of eastern United States. Highest counts were from South Carolina with over 3,000 wintering birds; numbers approached 2,000 birds in coastal Virginia. Counts of less than 600 were from Georgia and North Carolina. Ninety percent of oystercatchers were roosting on wind produced shell mounds along salt marsh channels. The remaining birds occurred in singles or pairs along barrier island beach fronts. Average roost size was 106 birds (range 18-390). Surveys were most efficient two hours from high tide when all birds were roosting. Wintering flocks in all states south of South Carolina probably consist primarily of breeding birds from those states, whereas Virginia and North Carolina have both breeding and wintering birds. All roosting birds used edges of tidal creeks and (primarily) commercial oyster beds fo...
Waterbirds, 2017
Information on demographic parameters needed to inform conservation strategies for American Oystercatchers (Haematopus palliatus) is lacking. The population dynamics of American Oystercatchers in Virginia, USA, were examined using a multi-state analysis framework that modeled movement of American Oystercatchers into and out of the State. Change in breeding status, age-specific survival rates, and age at first breeding were investigated for three geographically distinct study sites. Non-breeding American Oystercatchers originating from Virginia readily moved in and out of the State among years. The immigration rate for birds breeding on barrier islands was 6%. Emigration rates were 6% for the barrier island breeding population and 17% for the seaside lagoon population. Stage-specific annual survival rates were 0.66, 0.95 and 0.91 for juvenile, sub-adult and adult stages, respectively. Age at first breeding peaked in the fourth year for both the barrier island and seaside lagoon breeding populations. Movement and recruitment rates suggested that the barrier islands may provide the highest quality breeding habitat among the three study sites. This study showed that Virginia's American Oystercatcher population is linked with other Atlantic Coast populations, and these links should be considered when evaluating local population trends and management targets.
2004
Fisheries and other human activities pose a global threat to the marine environment. Marine protected areas (MPAs) are an emerging tool to cope with such threats. In the Dutch Wadden Sea, large MPAs (covering 31% of all intertidal flats) have been created to protect shellfish-eating birds and allow recovery of important habitats. Even though shellfish fishing is prohibited in these areas, populations of shellfish-eating birds in the Wadden Sea have declined sharply. The role of shellfish fisheries in these declines is hotly debated, therefore, we investigated the effectiveness of MPAs for protecting oystercatcher (Haematopus ostralegus) populations. Shellfish stocks (cockles, Cerastoderma edule) were substantially higher in the MPAs, but surprisingly this has not resulted in a redistribution of wintering oystercatchers. Oystercatchers in unprotected areas had less shellfish in their diet and lower condition (a combined measure of mass and haematological parameters), and their estimated mortality was 43% higher. It is likely, therefore, that shellfish fishing explains at least part of the 40% decline in oystercatcher numbers in recent years. Condition and mortality effects were strongest in males, and the population sex ratio was female biased, in agreement with the fact that males rely more on shellfish. The unprotected areas apparently function as an "ecological trap," because oystercatchers did not respond as anticipated to the artificial spatial heterogeneity in food supply. Consequently, the MPAs are effective on a local scale, but not on a global scale. Similar problems are likely to exist in terrestrial ecosystems, and distribution strategies of target species need to be considered when designing terrestrial and marine protected areas if they are to be effective. Atkinson, P. W., Clark, N. A., Clark, J. A., Bell, M. C., Dare, P. J., and Ireland, P. L. 2000. The effects of changes in shellfish stocks and winter weather on shorebird populations: results of a 30 year study on the Wash, England. BTO research report 238. British Trust for Ornithology, Thetford, UK. Beukema, J. J. 1993. Increased mortality in alternative bivalve prey during a period when the tidal flats of the Dutch Wadden Sea were devoid of mussels. Netherlands Journal of Sea Research 31:395-406.
Journal of Applied Ecology, 2001
1. Human interests often conflict with those of wildlife. In the coastal zone humans often exploit shellfish populations that would otherwise provide food for populations of shorebirds (Charadrii). There has been considerable debate on the consequences of shellfishing for the survival of shorebirds, and conversely the effects of shorebird predation on the shellfish stocks remaining for human exploitation. Until now, it has been difficult to determine the impact of current shellfishery practices on birds or to investigate how possible alternative policies would affect their survival and numbers. 2. One long-running contentious issue has been how to manage mussel Mytilus edulis and cockle Cerastoderma edule shellfisheries in a way that has least effect on a co-dependent shorebird, the oystercatcher Haematopus ostralegus , which also consumes these shellfish. This study used a behaviour-based model to explore the effects that the present-day management regimes of a mussel (Exe estuary, UK) and a cockle (Burry inlet, UK) fishery have on the survival and numbers of overwintering oystercatchers. It also explored how alternative regimes might affect the birds. 3. The model includes depletion and disturbance as two possibly detrimental effects of shellfishing and some of the longer-term effects on shellfish stocks. Importantly, model birds respond to shellfishing in the same ways as real birds. They increase the time spent feeding at low tide and feed in fields and upshore areas at other times. When shellfishing removes the larger prey, birds eat more smaller prey. 4. The results suggest that, currently, neither shellfishery causes oystercatcher mortality to be higher than it would otherwise be in the absence of shellfishing; at present intensities, shellfishing does not significantly affect the birds. However, they also show that changes in management practices, such as increasing fishing effort, reducing the minimum size of shellfish collected or increasing the daily quota, can greatly affect oystercatcher mortality and population size, and that the detrimental effect of shellfishing can be greatly increased by periods of cold weather or when prey are unusually scarce. By providing quantitative predictions of bird survival and numbers of a range of alternative shellfishery management regimes, the model can guide management policy in these and other estuaries.
2015
The purpose of this project was to assess the mussel (Mytilus edulis) food requirements of oystercatcher (Haematopus ostralegus) in the Exe Estuary, which has been designated a Special Protection Area for overwintering waterbirds, including oystercatcher. The overwintering oystercatcher population of the Exe Estuary has been well-studied, and the birds are known to feed predominantly upon mussels in intertidal areas. There have been recent declines in the population size of oystercatcher in the Exe Estuary, mirroring wider declines throughout Europe, the reasons for which are unknown. The study comprised: • The collection of new data on the area of mussel beds, the density and size distribution of mussels on these beds, and the numbers and behaviour of oystercatcher on these beds; • The collation of existing data on the food supply of oystercatchers in the Exe Estuary; • The development of models to predict the food requirements of oystercatcher; • Running simulations of the models to predict whether there is / could be any effect on oystercatcher survival of the current / potential future ways of managing the mussel fishery on the Exe Estuary. The current mussel fishery on the Exe provides a feeding resource for oystercatcher on intertidal lays that are exposed on spring tides. Two potential management options that could be effective at improving the feeding conditions of oystercatcher would be to increase the number and area of intertidal mussel lays, and / or to place mussel discards at a relatively high shore level close to the oystercatcher roost. This project documented a number of changes that have occurred to the Exe Estuary mussel and oystercatcher populations including: • The number and size of mussel beds have decreased since traditional methods of maintaining mussel beds in the estuary have ceased. • The density of mussels within the size range consumed by the birds has generally decreased, but the density of the larger mussels within this size range, which are more profitable to oystercatcher, has generally increased. • Oystercatcher lose a higher proportion of mussels to attacks by carrion crows and herring gulls than they have in the past. • The number of oystercatcher wintering in the estuary has declined, but the number of birds feeding on the mussel beds has been relatively stable. The models developed in the project predict that the present day mussel population is sufficient to support the number of oystercatcher that were observed to feed on mussels. The presence of mussel lays provides extra food for oystercatcher when these lays are exposed on spring tides. The present area, or increases in the area of mussel lays could increase the survival rate of oystercatcher if the number of birds feeding on mussels was over 2000. Below this threshold, starvation was predicted to affect 0 % of the population and so additional food resources cannot further reduce the starvation. The effect over 2000 birds is relatively small because the lays are only exposed for a short time, and so oystercatcher will obtain the majority of their food from mussel beds that are higher on the shore, and hence exposed for longer. Simulations were not run in which lays were positioned higher on the shore because this would not be commercially viable from a fishery perspective; the growth rate of mussels declines as they are positioned further up the shore because they are inundated with water for less time and so have less time to feed. Factors that would affect the beneficial effect of discards include the size of the discards, the size of the discard bed and the date from which discards are replenished. Our simulations predicted that larger discards spread at lower density over a larger bed increased oystercatcher survival by the greatest amount. This happened because interference competition excluded some birds from smaller patches, and oystercatcher can maintain high intake rate down to low mussel densities. It is unlikely that the size of discards could be increased, but the simulations suggest that the greatest benefit to oystercatchers could be achieved by spreading discards over a larger area. Our simulations predicted that making discards available from January increased oystercatcher survival by the same amount as making them available from September. This was because the feeding conditions of birds deteriorate through winter as, for example, the ash-free dry mass of prey declines, interference competition intensifies and day length shortens. The intake rate of birds feeding on discards was not measured during the study, but we recommend that this is done to between understand the potential benefit of discards. We recommend that the best place for the discard bed would be along the top of the shore on an area of gravel (and hence of relatively low food value to the birds), to the south of Cockwood. This is south of an area where discards have been laid and exploited by oystercatcher in the past, but would experience lower levels of disturbance from human activity.