4. SOME BIRDS OBSERVED AT LAKE MENTZ

Randall, R. M. &; Randall, B. M. 1900. The hard-shell4 diet of African Black Oystercatcher chicks at St Croix Island, South Africa. Ostrich 53:157-163.

The hard-shelled diet of African Black Oystercatcher Haematopus moquini chicks was established by monitoring piles of food remains brought to the chicks. Mussels were the dominant prey species constituting about 90% numerically and about 95% by mass. Limpets were the next most abundant prey item, while false limpets, keyhole limpets and whelks were present in small numbers. Transects down the intertidal area showed that African Black Oystercatchers ignored some abundant species such as barnacles and small gastropods. They took most prey species in the same relative proportion that they were represented in transects, but there was evidence of selection for limpets and avoidance of false limpets and whelks. The modal size class of mussels in feeding piles was greater than in transects.     

Selenium status inCharadriiformes

The distribution of selenium in a marine wader, the Oystercatcher (Haematopus ostralegus) is given by the levels in 15 tissues and plasma. Red blood cells (RBC) contain the highest level (23 mg/kg dry wt) followed by liver, lung, and kidney (17–19 mg/kg). Most other tissues range from 3–10 mg/kg. The average kidney and liver concentrations of the Oystercatcher belong to the concentrations characteristic in birds. However, the Oystercatcher's tissue selenium concentrations are in general four-to fivefold mammalian levels, but in liver and lung, 11- to 13-fold and in the RBC, 12- to 33-fold. The selenium plasma and RBC levels of the Oystercatcher vary during the year from 280 to 410 μg/L and 13 to 30 mg/kg dry wt, respectively; the plasma concentrations are positively correlated with the RBC selenium concentrations. An overview of literature data shows that the selenium kidney and liver concentrations of birds do not vary with geographical latitude and size (length) of the birds. In species of the ordersCharadriiformes andProcellariiformes, high selenium kidney, and to a lesser extent liver, concentrations may occur. A function of selenium in antioxidation is suggested.     

THE POPULATION,ECOLOGY AND CONSERVATION OF THE BLACK OYSTERCATCHER HAEMATOPUS MOQUINI

Summers, R. W. & Cooper, J. 1977. The population, ecology and conservation of the Black Oystercatcher Haematopus moquini. Ostrich 48:28-40.

The population of Black Oystercatchers Haematopus moquini in the southwestern Cape, South Africa, was estimated to be 2 942 birds. Birds occurred most abundantly on coastal islands and were also abundant on mixed (sandy and rocky) shores of the mainland. Sandy shores and coastal wetlands supported few birds. Black Oystercatchers bred mainly from December to February with the number of clutches present reaching a peak in the first half of January. The most frequent clutch size was two eggs, the mean clutch size was 1,81. No significant differences were found in either linear dimensions or mass between the first and second eggs. The mean proportion of juveniles in groups of birds in July was 3,6 % suggesting a low recruitment to the adult population. The breeding population at Marcus Island is apparently sedentary throughout the year. The primary moult season for adults extends from March to October (eight months). Introduced mammalian predators should be controlled on islands and important mainland breeding sites should be protected by the creation of nature reserves and restricting human access during the breeding season.     

A preliminary study on the effects of oyster culturing structures on birds in a sheltered Irish estuary

This study investigated the species composition, numbers and behaviour of birds in an intertidal oyster culture area in Cork Harbour . These data were compared to a nearby area free of aquaculture within the same estuary in March 1999. Species which occurred in the aquaculture free area were also observed in the trestle-area. The most abundant species were oystercatcher Haematopus ostralegus, redshank Tringa totanus, dunlin Calidris alpina, curlew Numenius arquata, black-headed gull Larus ridibundus and common gull Larus canus. Oystercatcher, curlew, black-headed gull and common gull occurred in significantly lower numbers in the trestle area, while for redshank and dunlin the differences were not significant. The percentage of birds feeding did not differ between the two areas. Oystercatcher, redshank, dunlin and curlew mostly fed in both areas. In contrast, black-headed gull and common gull generally did not feed, but surveyed the area. Whether the trestles were covered by oyster bags or not did not have any effect on the number of birds except for the dunlin. Dunlin were significantly more frequent beneath the trestles with bags compared with those without bags. In general, the percentage of birds feeding did not differ between areas. Interspecies differences occurred with regard to the position occupied by birds at the trestles. Oystercatcher, redshank and curlew spent more time underneath the trestles. Dunlin, black-headed gulls and common gulls did not differ in numbers underneath or on top of the trestles. These preliminary observations at a single time period give some insight as to the potential interactions between shellfish aquaculture and intertidal birds.     

OBSERVATIONS ON THE COMMUNAL ROOSTING OF AFRICAN BLACK OYSTERCATCHERS

Hockey P. A. R. 1985. Observations on the communal roosting of African Black Oystercatchers. Ostrich 56: 52–57.

There are currently three main hypotheses for the adaptive significance of avian communal roosts: physiological advantages, predator avoidance and information centres. The African Black Oystercatcher Haematopus moquini is territorial throughout the year and forms communal roosts during the nonbreeding season, but does not breed communally. Roosts generally are small, and site fidelity is high. Roosts are normally sited on a rocky promontory with adjacent offshore rocks (west coast), or in flat areas with extensive all-round visibility. The main predators of African Black Oystercatchers are nocturnal terrestrial mammals and nocturnal communal roosts are larger and more tightly packed than daytime roosts. Breeding birds do not roost communally during the breeding season and at this time of year mortality due to mammal predators at a study site in Saldanha Bay was greatest (X² = 9.46; p<0.01). It appears therefore that predator avoidance is an important adaptive feature of communal roosting in this species.     

4. NOTES ON THE BIRDS OF THE VAN RYNEVELD'S PASS IRRIGATION LAKE,GRAAFF-REINET

McLachlan, A., Woodridge, T., Schramm, M. &; Kühn, M. 1980. Seasonal abundance, biomass and feeding of shore birds on sandy beaches in the Eastern Cape, South Africa. Ostrich 51:44-52.

The numbers of birds on three Eastern Cape sandy beaches were monitored monthly over one year during 1977/78. Dominant among 17 species were the Southern Blackbacked Gull Larus dominicanus, Black Oystercatcher Haematopus moquini, Whitefronted Sandplover Charadrius marginatus and Sanderling Calidris alba. These four species made up 95% of bird numbers and their respective biomass values were 78 652, 7 695, 578 and 3 116 kJ/km shoreline. Total food consumption for these species, calculated on the basis of estimated standard metabolic rates, was 4 159 394, 521 149, 76 768 and 363 053 kJ/km respectively. Food composition and feeding behaviour are also discussed and the total quantity of intertidal macrobenthic animals consumed by birds estimated.     

6. THE PROBLEM OF NOMENCLATURE

Hockey, P. A. R. 1983. Aspects of the breeding biology of the African Black Oystercatcher. Ostrich 54:26-35. Fifty-five pairs of African Black Oystercatchers Haematopus moquini bred at Marcus Island in 1979–1980. Sixteen pairs laid replacement clutches: the mean interval between loss of the fist clutch and laying of a replacement clutch was 22,2 days. Mean inter-nest distance was 19,4 m. The modal clutch size was 2, with a mean of 1.74. Mean dimensions of 105 eggs were 60,7 × 40,l mm and mean fresh egg mass was 55,s g. There were differences in egg mass and dimensions between eggs in one- and two-egg clutches. Rate of egg loss was high, due mainly to depredation by Kelp Gulls Larus dominicanus promoted by human disturbance. Fledging success was lower at a disturbed site than at undisturbed sites, with highest chick mortality occurring in the first week of life. Mortality of first-year birds of eight days and older was estimated at 48% and 69% in two successive seasons. All juvenile birds dispersed from the natal sites, and were resighted up to 168 km away. Dispersed juveniles were concentrated at the edge of an area of high oystercatcher density.     

Umweltchemikalien in Eiern des Alpenstrandl?ufers (Calidris alpina) aus Nordnorwegen im Vergleich zu Eiern von Brutvogelarten des Wattenmeeres

Zusammenfassung Im Frühjahr 1993 wurden die Konzentrationen von 20 organischen Umweltchemikalien sowie von Quecksilber in den Eiern von acht Brutvogelarten im Gebiet der Wattenmeerinsel Spiekeroog ermittelt (BrandgansTadorna tadorna; EiderenteSomateria mollissima; AusternfischerHaematopus ostralegus; S?belschn?blerRecurvirostra avosetta; RotschenkelTringa totanus; Lachm?weLarus ridibundus; Silberm?weLarus argentatus; Flu?seeschwalbeSterna hirundo) und mit Eiern des Alpenstrandl?ufers (Calidris alpina alpina) von einem Brutplatz in Nordnorwegen (Gamvik) verglichen. Die dortigen V?gel nutzen das Wattenmeer au?erhalb der Brutzeit. H?chste Σ-PCB wiesen Flu?seeschwalben- und Silberm?weneier auf. Quecksilber war in Eiern von Eiderente, Austernfischer und Flu?seeschwalbe am h?chsten konzentriert sowie Σ-DDT in Lachm?weneiern. Bromocyclen konnten in keiner Eiprobe der acht Wattenmeerarten nachgewiesen werden, Moschusxylol in 29% und Octachlorstyrol in 57%. Die Umweltchemikalienkonzentrationen lagen in den meisten F?llen über der gesetzlichen H?chstmenge bzw. dem Richtwert für Eier, die zur menschlichen Ern?hrung bestimmt sind, erreichten aber wahrscheinlich keine den Bruterfolg gef?hrdenden Konzentrationen. Im Vergleich zu den Rückst?nden in den Eiern der acht Brutvogelarten des Wattenmeeres waren die Eier des Alpenstrandl?ufers aus Nordnorwegen moderat belastet und zeigten ein ?hnliches Umweltchemikalienmuster wie Eier von nicht ganzj?hrig im Wattenmeer anwesenden Watvogelarten. Beim Alpenstrandl?ufer konnten erstmalig Bromocylen-Rückst?nde in Vogeleiern nachgewiesen werden.

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Environmental chemicals in eggs of Dunlins (Calidris alpina) from Northern Norway compared to eggs of coastal bird species breeding in the Wadden Sea

Summary Owing to the international importance of the Wadden Sea for waders and waterfowl a long-term program to monitor chemical contamination of birds breeding in the Wadden Sea has been established in the early 1980s with Oystercatcher (Haematopus ostralegus) and Common Tern (Sterna hirundo) as monitor species. However, numbers of birds breeding in the area are only 10% compared to numbers of birds using it as a wintering, moulting or staging area, and little is known about contamination of those non-breeding birds. In 1993 we compared contamination levels in eggs from eight species (ShelduckTadorna tadorna; EiderSomateria mollissima; Oystercatcher; AvocetRecurvirostra avosetta; RedshankTringa totanus; Black-headed GullLarus ridibundus; Herring GullLarus argentatus; Common Tern) breeding at the island of Spiekeroog (German Wadden Sea) with those from Dunlins (Calidris alpina alpina) breeding in Northern Norway (Gamvik). It is known that many Dunlin from this area use the German Wadden Sea for staging. We analyzed contaminant levels of 21 industrial chemicals (PCBs, HCB, Moschusxylol, Octachlorstyrol, Mercury) and biocides (DDT and metabolites, HCH-Isomers, Bromocyclen). Common Tern and Herring Gull eggs reached highest Σ-PCB levels whereas mercury had the highest concentrations in eggs of Eider, Oystercatcher and Common Tern as well as Σ-DDT in eggs of Black-headed Gull. Bromocyclen could not be detected in eggs of the breeding species, whereas Moschusxylol was found in 29% of the eggs and Octachlorostyrol in 57%. Contaminant levels were in most cases above the levels given by German law for eggs used for human food but are probably not high enough to show an effect on the breeding success of the different species. In comparison to these results contaminant levels in eggs of Dunlins from Northern Norway were low and showed a similar chemical pattern as for migrating waders breeding in the Wadden Sea detected. For the first time Bromocyclen residues could be detected in bird eggs.

     

The introduced clam Ensis americanus in the Wadden Sea: field experiment on impact of bird predation and tidal level on survival and growth

In the Danish Wadden Sea the intertidal distribution of the introduced bivalve Ensis americanus (syn. E. directus) is restricted to a narrow zone around the mean low water level. To test the possible impact of birds and submersion time on dynamics and distribution of the clams, adult specimens of E. americanus collected near the low water line were transplanted to two intertidal sites and established in open and net-covered experimental plots for 9 weeks (autumn 2001). The lowest survival of clams was registered at the low-shore-site (LSS) in plots open to bird predators, suggesting that birds such as Common Eider (Somateria mollissima) or Oystercatcher (Haematopus ostralegus) may control the abundance of E. americanus at the lower tidal levels. For clams showing increment in shell length during the study period, the shell growth rates were highest at the LSS and lowest in the open plots at the high-shore-site (HSS). Differences in immersion time and thus food supply may explain this pattern. Body mass index (BMI) of the clams showed basically the same pattern as the survivorship: lowest BMI in open plots at the LSS and highest in the covered plots at this site. Clams from the HSS were intermediate in their BMI. Disturbance by birds in the open plots at the LSS may explain the low BMI. In conclusion birds may be an important factor controlling abundance of E. americanus in the lower intertidal zone.     

Competitive abilities of oystercatchers ( Haematopus ostralegus ) occupying territories of different quality

In territorial species, habitat heterogeneity results in some individuals occupying poor quality sites while others occupy high quality sites. Floaters (mature nonbreeders) may accept a low quality territory, because it is the best they can get and defend (‘inferior phenotype hypothesis’), or because it is a strategic alternative for a high quality territory in the long run (‘queue hypothesis’). Oystercatcher Haematopus ostralegus territories differ consistently in the amount of offspring produced each year and this is related to the distance between the nesting and feeding territories. The inferior phenotype hypothesis was previously rejected on the basis of the absence of morphometric differences (assumed to indicate competitive abilities) among breeders. We investigated social dominance, in the field and in captivity, in relation to the quality of the breeding territory. In the field, birds with high-quality territories won more often compared to those occupying low-quality territories. However, this difference was not apparent in a small dataset of captive birds. These results are discussed in the framework of the long-term fitness prospects of settling in a high or low quality territory.     

MORPHOMETRICS AND SEXING OF THE AFRICAN BLACK OYSTERCATCHER

Summary

Hockey, P. A. R. 1981. Morphometries and sexing of the African Black Oystercatcher. Ostrich 52: 244–247.

109 African Black Oystercatchers Haematopus moquini were caught, measured and sexed by cloacal examination during the 1979/1980 breeding season. Six standard taxonomic variables were measured. Females were larger than males in all dimensions considered. The most dimorphic characters were mass and exposed culmen length. The data were subjected to stepwise discriminant analysis and a linear function was derived which allowed birds of unknown sex to be sexed. The function is D = ?0,391x₁ ?0,016 x₂ +0,218 x₃ +0,714 x₄ +15,946 where x₁ = exposed culmen length (mm), x₂ = body mass (g), x₃ = length of tarsometatarsus (mm) and x₄ = culmen depth at the gonys. Values of D from the above equation less than zero indicate a female while those greater than zero indicate a male. The greater the divergence of D from zero, the higher the probability of correctly sexing an unknown individual: once D> ± 1,2, p>0,99.     

Energetics of growth in semi-precocial shorebird chicks in a warm environment: the African black oystercatcher, Haematopus moquini

We studied prefledging growth, energy expenditure and time budgets of African Black Oystercatcher, Haematopus moquini, chicks on Robben Island, Western Cape, South Africa. The aim of the study was to investigate the effect of parental feeding on the growth and energetics of semi-precocial shorebird chicks. Chicks reached mean fledging mass, 463 g, in 40 days. The growth rate coefficient of African Black Oystercatcher chicks was 2% below the predicted value for a shorebird species of their body mass, but it was smaller than that of other precocial and semi-precocial shorebirds to date. Resting metabolic rate (RMR, measured through respirometry), daily metabolisable energy (DME), defined as daily energy expenditure (DEE, measured with doubly labelled water) plus energy deposited into tissue (E(tis)), and total metabolisable energy (TME) of African Black Oystercatcher chicks were similar to those expected for a species of their body size. DEE was not influenced by weather (ambient temperature, operative temperature and wind speed), therefore, variations in DEE may be explained by body mass alone. The relative RMR of the African Black Oystercatcher was greater, their TME was approximately the same, their average daily metabolisable energy (ADME) was less, and they spent less time foraging (short periods of parental feeding) and more time inactive than three precocial species in the Western Cape. Therefore, the semi-precocial mode of development of African Black Oystercatcher chicks reduced energy costs from thermoregulation and activity, and they were able to grow relatively faster than precocial, self-feeding shorebird species in similar climatic conditions. The growth rate coefficient of African Black Oystercatcher chicks was smaller than that of Eurasian Oystercatcher, Haematopus ostralegus, chicks, which may be a consequence of differences in body size and latitudinal effects.     

Off‐road vehicles affect nesting behaviour and reproductive success of American Oystercatchers Haematopus palliatus

As human populations and associated development increase, interactions between humans and wildlife are occurring with greater frequency. The effects of these interactions, particularly on species whose populations are declining, are of great interest to ecologists, conservationists, land managers and natural resource policy‐makers. The American Oystercatcher Haematopus palliatus, a species of conservation concern in the USA, nests on coastal beaches subject to various forms of anthropogenic disturbance, including aircraft overflights, off‐road vehicles and pedestrians. This study assessed the effects of these human disturbances on the incubation behaviour and reproductive success of nesting American Oystercatchers at Cape Lookout National Seashore, on the Atlantic coast of the USA. We expanded on‐going monitoring of Oystercatchers at Cape Lookout National Seashore by supplementing periodic visual observations with continuous 24‐h video and audio recording at nests. Aircraft overflights were not associated with changes in Oystercatcher incubation behaviour, and we found no evidence that aircraft overflights influenced Oystercatcher reproductive success. However, Oystercatchers were on their nests significantly less often during off‐road vehicle and pedestrian events than they were during control periods before the events, and an increase in the number of off‐road vehicles passing a nest during incubation was consistently associated with significant reductions in daily nest survival (6% decrease in daily nest survival for a one‐vehicle increase in the average number of vehicles passing a nest each day; odds ratio = 0.94; 95% confidence interval (CI) 0.90, 0.98) and hatching success (12% decrease in hatching success for a one‐vehicle increase in the average number of vehicles passing a nest each day; odds ratio = 0.88; 95% CI 0.76, 0.97). Management of vehicles and pedestrians in areas of Oystercatcher breeding is important for the conservation of American Oystercatchers.     

Bucking the trend: the African Black Oystercatcher as a recent conservation success story

The African Black Oystercatcher Haematopus moquini is a charismatic, southern African near-endemic, wader species, that is often seen as a flagship species for coastal bird conservation, as it was recently down-listed regionally to Least Concern on the IUCN Red List of Threatened Species. To celebrate this rare conservation success story, BirdLife South Africa named it the 2018 Bird of the Year and ran a year-long programme in collaboration with the Nature’s Valley Trust highlighting aspects of the species’ biology, current threats, and conservation success. We used data collected by the Southern African Bird Atlas Project (SABAP1 and SABAP2) to examine changes in the species’ range and relative abundance, both in the records between the two projects, as well as trends within the SABAP2 sampling period (2008–2017). This case study enabled us to assess whether such metrics can accurately reflect abundance and distributional changes in a species. We found increases in the reported range and the reporting rates between the two Atlas projects, and that the SABAP2 reporting rate was stable. Regionally, across four coastal categories, the reporting rate was lowest in KwaZulu-Natal, though this region also showed an increase in the probability of reporting during the SABAP2 period. While corroborating the recent change in the species’ conservation status, we also provide good evidence that the long-term SABAP data can be used successfully to assess population trends and range changes over time.     

Book Reviews

Adams, N.J., Kerley, G.I.H. & Watson, J.J. 1999. Disturbance of incubating African Black Oystercatchers: is heating of exposed eggs a problem? Ostrich 70(3&4): 225–228.

We measured temperatures of incubated and exposed eggs of African Black Oystercatchers Haematopus moquini nesting in coastal dunes, Algoa Bay, South Africa through three of the 10 hottest days of summer during the 1994/95 breeding season. Mean incubation temperature was 34.4 ± 0.7°C (range: 32.2–37.0; n=3). The average maximum temperature attained by exposed dummy eggs, averaged higher at 37.4 ± 2.7°C (n=5). The absolute maximum recorded for exposed eggs was 40.1°C. These temperatures are within lethal limits measured for other birds and suggests that heating of exposed eggs after disturbance of incubating was not a direct factor in explaining variation in breeding success of oystercatchers in the Alexandria Dunefield, Algoa Bay.     

Spatially Extended Habitat Modification by Intertidal Reef-Building Bivalves has Implications for Consumer-Resource Interactions

Ecosystem engineers can strongly modify habitat structure and resource availability across space. In theory, this should alter the spatial distributions of trophically interacting species. In this article, we empirically investigated the importance of spatially extended habitat modification by reef-building bivalves in explaining the distribution of four avian predators and their benthic prey in the Wadden Sea—one of the world’s largest intertidal soft-sediment ecosystems. We applied Structural Equation Modeling to identify important direct and indirect interactions between the different components of the system. We found strong spatial gradients in sediment properties into the surrounding area of mixed blue mussel (Mytilus edulis) and Pacific oyster (Crassostrea gigas) reefs, indicating large-scale (100s of m) engineering effects. The benthic community was significantly affected by these gradients, with the abundance of several important invertebrate prey species increasing with sediment organic matter and decreasing with distance to the reefs. Distance from the reef, sediment properties, and benthic food abundance simultaneously explained significant parts of the distribution of oystercatchers (Haematopus ostralegus), Eurasian curlews (Numenius arquata), and bar-tailed godwits (Limosa lapponica). The distribution of black-headed gulls (Chroicocephalus ridibundus)—a versatile species with many diet options—appeared unaffected by the reefs. These results suggest that intertidal reef builders can affect consumer-resource dynamics far beyond their own boundaries, emphasizing their importance in intertidal soft-bottom ecosystems like the Wadden Sea.     

The decline of a population of farmland breeding waders: a twenty-five-year case study

Capsule: Changes in sward height, driven by changes in management, were associated with a large decline in a population of farmland breeding waders.

Aims: To examine the relationship between changes in habitat and numbers of breeding wader on an area of Scottish farmland over the last 25 years.

Methods: Nesting waders in a core survey area of 7.5?km² were monitored annually from 1990 to 2015. An additional 10.3?km² were monitored less frequently. Habitat characteristics of each field were recorded and breeding success by Lapwing determined in a sample of fields.

Results: All species showed large declines over the study period, Oystercatcher Haematopus ostralegus by 95%, Lapwing Vanellus vanellus by 88%, Curlew Numenius arquata by 67% and Redshank Tringa totanus by 87% from peaks of 125, 365, 57 and 53 pairs, respectively. Changes in spring sward height, considered to be due to changes in crop type, were associated with changes in the numbers of breeding waders over time. Productivity by a sample of Lapwings was unchanged through the study period.

Conclusion: Short swards, especially bare till, in spring appear to have been important in contributing to the maintenance of an assemblage of breeding waders in mixed arable-pasture farmland. The decline appeared greater than could be accounted for by losses of preferred habitats alone.     

Chemotaxonomische untersuchungen an limikolen: Die zusammensetzung des bürzeldrüsensekretes von austernfischer, rotschenkel, knutt und alpenstrandläufer

The fatty acid and alcohol composition of the uropygial gland wax from four species of birds of the order Laro-limicolae was investigated. Compounds were identified by GLC-MS and the major components were found to be mono-, di and tri-methyl-branched fatty acids and n-, mono- and di-methyl-substituted alcohols. The wax patterns of the three species of the family Scolopacidae (Tringa totanus L., Calidris canutus L., Calidris alpina L.) were shown to be closely related and different from that of the oystercatcher (Haematopus ostralegus L.) by the occurrence of trimethyl-substituted fatty acids and dimethyl-substituted alcohols. In contrast to the species of Scolopacidae, the substituents in the monomethyl-branched alcohols of the oystercatcher are exclusively located in postions near the aliphatic end of the molecule. There are some relationships in uropygial gland wax composition between the Scolopacidae and the Alicae and Laridae.

Résumé

Die Zusammensetzung der Bürzelwachsbestandteile von vier Vertretern der Larolimicolae wurde mit Hilfe der GLC-MS-Kombination bestimmt. Hauptbestandteile sind mono-, di- und tri-methyl-verzvveigte Fettsäuren sowie n-, Mono- und Di-methyl-alkanole. Die Bürzelwachsmuster dieser Arten aus der Familie Scolopacidea (Tringa totanus L., Calidris canutus L., Calidris alpina L.) sind untereinander sehr ähnlich, unterscheiden sich jedoch von dem des Austernfischers (Haematopus ostralegus L.) durch das Auftreten von trimethylsubstituierten Fettsäuren und dimethyl-substituierten Alkoholen. Im Gegensatz zu den ScolopacidaeArten liegt die Methylverzweigung der Methylalkanole beim Austernfischer ausschlieβlich im aliphatischen Molekülende. Es existieren chemotaxonomische Beziehungen der Familie Scolopacidae zu den Alcidae und Laridae.     

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.