Haematopus Palliatus Research Articles

POPULATION SIZE AND WINTER DISTRIBUTION OF EASTERN AMERICAN OYSTERCATCHERS

Conservation of the eastern subspecies of the American oystercatcher (Haematopus palliatus palliatus) is a high priority in the U.S. Shorebird Conservation Plan, but previous population estimates were unreliable, information on distribution and habitat associations during winter was incomplete, and methods for long-term monitoring had not been developed prior to this survey. We completed the aerial survey proposed in the U.S. Shorebird Conservation Plan to determine population size, winter distribution, and habitat associations. We conducted coastal aerial surveys from New Jersey to Texas during November 2002 to February 2003. This area comprised the entire wintering range of the eastern American oystercatcher within the United States. Surveys covered all suitable habitat in the United States for the subspecies, partitioned into 3 survey strata: known roost sites, high-use habitat, and inter-coastal tidal habitat. We determined known roost sites from extensive consultation with biologists and local experts in each state. High-use habitat included sand islands, sand spits at inlets, shell rakes, and oyster reefs. Partner organizations conducted ground counts in most states. We used high resolution still photography to determine detection rates for estimates of the number of birds in particular flocks, and we used ground counts to determine detection rates of flocks. Using a combination of ground and aerial counts, we estimated the population of eastern American oystercatchers to be 10,971 /− 298. Aerial surveys can serve an important management function for shorebirds and possibly other coastal waterbirds by providing population status and trend information across a wide geographic scale.

Breeding Season Status of the American Oystercatcher in Virginia, USA

Abstract Surveys of the American Oystercatcher (Haematopus palliatus) were conducted in all suitable nesting habitat in coastal Virginia, USA during the 2003 breeding season. The total of 588 pairs more than doubles previous estimates for the state, and provides a benchmark for the comparison of future surveys. These results suggest that Virginia supports the largest number of oystercatchers in the breeding season relative to other east coast states. Previous surveys in Virginia focused only on one coastal area, the barrier islands. Over two hundred pairs recorded in the seaside lagoon system of the Delmarva Peninsula in 2003 accounted for the large discrepancy between previous estimates for the state and the results of this survey. Over 89% of the total number of pairs was observed on the islands and in the lagoon system of the Delmarva Peninsula. Approximately 87% of the pairs were on land that is managed or regulated to some degree for the conservation of nesting birds by federal, state, municipal and ...

Using the Risk-Disturbance Hypothesis to Assess the Relative Effects of Human Disturbance and Predation Risk on Foraging American Oystercatchers

Abstract The risk-disturbance hypothesis asserts that animals perceive human disturbance similar to nonlethal predation stimuli, and exhibit comparable responses in the form of optimization tradeoffs. However, few studies have examined how natural predation risk factors interact with human-disturbance stimuli to elicit such responses. We observed American Oystercatcher (Haematopus palliatus) vigilance behavior from September–December 2002 on the Cape Romain National Wildlife Refuge, South Carolina. A set of models was constructed based on 340 focal-animal samples and models revealed relationships between vigilance behavior, predator density, and boat activity. Oystercatchers increased vigilance in response to aerial predators, particularly late in the season when predator species composition was dominated by Northern Harriers (Circus cyaneus). At a broader temporal scale, oystercatchers exhibited the highest vigilance rates during simultaneous peaks in boating disturbance and Osprey (Pandion haliaetus) activity. Due to this temporal overlap of stimuli, it is difficult to interpret what may have been driving the observed increased in vigilance. Foraging rates appeared to be primarily driven by habitat and tidal stage indicating that time lost to vigilance did not effectively reduce intake. Taken together, these findings provide some support for the risk-disturbance hypothesis, underscore the sensitivity of disturbance studies to temporal scale, and draw attention to the potential confounding effects of natural predation risk. Uso de la Hipótesis de Riesgo-Disturbio para Evaluar los Efectos Relativos de los Disturbios Humanos y del Riesgo de Depredación en Haematopus palliatus Resumen. La hipótesis de riesgo-disturbio propone que los animales perciben los disturbios causados por los humanos de un modo similar a como perciben estímulos de depredación no letales, y que exhiben respuestas comparables en términos de compromisos de optimización. Sin embargo, pocos estudios han examinado cómo interactúa el riesgo natural de depredación con los estímulos causados por disturbios humanos para causar dichas respuestas. Observamos el comportamiento de vigilancia del ostrero Haematopus palliatus entre septiembre y diciembre de 2002 en el Refugio Nacional de Vida Silverstre Cape Romain, South Carolina. Con base en 340 muestras de animales focales se construyeron una serie de modelos, los cuales mostraron relaciones entre el comportamiento de vigilancia, la densidad de depredadores y la actividad de botes. Los ostreros incrementaron la vigilancia como respuesta a los depredadores aéreos particularmente hacia el final de la temporada, cuando la composición de especies de depredadores estaba dominada por Circus cyaneus. A una escala temporal más amplia, los ostreros presentaron las tasas de vigilancia más altas durante picos simultáneos en los disturbios causados por botes y en la actividad de Pandion haliaetus. Debido a esta superposición de los estímulos es difícil interpretar cuál de ellos habría estado determinando el incremento en vigilancia observado. Las tasas de forrajeo parecieron estar dadas principalmente por el hábitat y la posición de la marea, lo que indica que el tiempo perdido en vigilancia no redujo la ingestión de alimento efectivamente. En conjunto, estos hallazgos proveen algo de evidencia que apoya la hipótesis de riesgo-disturbio, resaltan la sensibilidad a la escala temporal de los estudios sobre disturbios y enfatizan la necesidad de prestar atención a la posibilidad de que existan efectos enmascarados del riesgo de depredación natural.

Trophic facilitation by the oystercatcher Haematopus palliatus Temminick on the scavenger snail Buccinanops globulosum Kiener in a Patagonian bay

This study investigated the role of the American oystercatcher ( Haematopus palliatus) as a resource subsidizer for the scavenger snail Buccinanops globulosum in a northern Patagonian bay (40°45′S, 64°56′W, San Antonio Bay, Argentina). The most frequent food item for the snails was dead crabs Cyrtograpsus angulatus Dana, and the snails preferred this item. In the field, most dead crabs (78%) resulted from oystercatcher predation. Field densities of dead crabs were within the 95% confidence limits of the estimated densities produced by oystercatcher foraging activity, suggesting that a large proportion of carrion available for snails is a byproduct of oystercatcher predation. Dead crabs with injuries were more rapidly detected and consumed by snails, probably because injuries produced by oystercatchers increase leakage of body fluids and facilitate penetration of the proboscis of the snails. Our results suggest that oystercatcher predation subsidize this scavenger snail by increasing availability of food, decreasing variability in their provision and facilitating their consumption.

Identifying repaired shell damage and abnormal calcification in the stout razor clam Tagelus plebeius as a tool to investigate its ecological interactions

Analysis of acetate peels of shell sections of the stout razor clam Tagelus plebeius from the Mar Chiquita coastal lagoon (37° 32′S, 57°19′W, Argentina) revealed the presence of a series of repaired shell margin breaks and different types of abnormal calcifications on the inner surface of their valves. Shell damage and subsequent repair was observed in 73% of the specimens analysed (70.3% of them with scars in both valves around the shell margin, 54.5% with the posterior shell area damaged in one or both valves, 30% with more than one damage). There were only few sediment grains incorporated in the shell matrix when scars occurred around the shell margin. A field experiment suggests that this pattern of shell damage results from natural re-burrowing (vertical movement) activities. However, 10% of the individuals showed an inner shell alteration forming a blister full of sediment grains in the area of the shell pallial sinus. These blisters were associated with repaired shell breaks in the posterior part of the valve, which was confirmed with a field experiment. The development of such blisters could be an indirect consequence of sub-lethal predatory attacks by the American oystercatcher Haematopus palliatus, given that this species breaks the posterior part of the shells of stout razor clams when extracting them from the sediments. The third type of shell alteration (94.3% of the shells) was an orange to brown coloration on the inner shell surface concurrently with irregular carbonate deposition that, in some cases, results in the formation of localised calcium carbonate concretions. This pattern is associated with the presence of metacercariae of gymnophallid parasites. In conclusion, Tagelus plebeius is able to repair its shell after damage produced by different agents. These repairs are very distinctive and, thus, they can be used as evidence of interactions between this clam and its environment (e.g. sediment characteristics) and the associated community (e.g., predators, parasites).

A Comparison of American Oystercatcher Reproductive Success on Barrier Beach and River Island Habitats in Coastal North Carolina

American Oystercatcher (Haematopus palliatus) numbers along the east coast of the United States are declining in some areas and expanding in others. Researchers have suggested that movement from traditional barrier beach habitats to novel inland habitats and coastal marshes may explain some of these changes, but few studies have documented oystercatcher reproductive success in non-traditional habitats. This study compares the reproductive success of the American Oystercatcher on three river islands in the lower Cape Fear River of North Carolina with that of birds nesting on barrier island beach habitat of Cape Lookout National Seashore. There were 17.6 times more oystercatcher breeding pairs per kilometer on the river island habitat than barrier beach habitat. The Mayfield estimate of daily nest content survival was 0.97 (S.E. ± 0.0039) on river islands, significantly higher than 0.92 (S.E. ± 0.0059) on barrier islands. The primary identifiable cause of nest failure on the river islands was flooding while the main cause of nest failure on the barrier islands was mammalian predation. Fledging success was equally low at both study sites. Only 0.19 chicks fledged per pair in 2002, and 0.21 chicks fledged per pair in 2003 on the river islands and 0.14 chicks fledged per pair in 2002 and 0.20 chicks fledged per pair in 2003 on the barrier islands. Many questions are still unanswered and more research is needed to fully understand the causes of chick mortality and the functional significance of non-traditional nesting habitats for the American Oystercatcher in the eastern United States.

USING THE RISK-DISTURBANCE HYPOTHESIS TO ASSESS THE RELATIVE EFFECTS OF HUMAN DISTURBANCE AND PREDATION RISK ON FORAGING AMERICAN OYSTERCATCHERS

Abstract The risk-disturbance hypothesis asserts that animals perceive human disturbance similar to nonlethal predation stimuli, and exhibit comparable responses in the form of optimization tradeoffs. However, few studies have examined how natural predation risk factors interact with human-disturbance stimuli to elicit such responses. We observed American Oystercatcher (Haematopus palliatus) vigilance behavior from September–December 2002 on the Cape Romain National Wildlife Refuge, South Carolina. A set of models was constructed based on 340 focal-animal samples and models revealed relationships between vigilance behavior, predator density, and boat activity. Oystercatchers increased vigilance in response to aerial predators, particularly late in the season when predator species composition was dominated by Northern Harriers (Circus cyaneus). At a broader temporal scale, oystercatchers exhibited the highest vigilance rates during simultaneous peaks in boating disturbance and Osprey (Pandion haliaetus) ac...

Small- and large-scale effect of the SW Atlantic burrowing crab Chasmagnathus granulatus on habitat use by migratory shorebirds

Here we address the question of whether the presence of the burrowing crabs Chasmagnathus granulatus affects small- and large-scale habitat use by migrant shorebirds. This crab is the dominant species in soft bare sediments and vegetated intertidal areas along the SW Atlantic estuaries (southern Brazil 28°S to the northern Argentinean Patagonia 42°S). They generate very extensive burrow beds in soft bottom intertidal areas. Our information shows that this burrowing crab affects the small-scale habitat use by shorebirds, given that shorebirds never walk through the funnel-shaped entrances of burrows. Given that crab burrow entrances occupy up to 40% of the intertidal area, there is a large decrease of available shorebird habitat in crab beds, restricting their activity to the spaces between the burrows. The southern migratory shorebird Charadrius falklandicus maximize the use of these areas by foraging closer to the burrows than the other bird species. Neotropical migrants, such as Calidris fuscicollis, Pluvialis squatarola and Tringa melanoleuca, used foraging paths that tended to maximize the distance from burrows, especially the distance to larger burrows. A field experiment showed that this was not necessarily due to a decrease in the availability of polychaetes near the crab burrows. A combination of landscape measurements and satellite images showed that crab beds covered up to 40% of the intertidal area of the Mar Chiquita coastal lagoon (37°40′S, Argentina), and nearly 100% of the intertidal area of the Bahia Blanca estuary (38°48′–39°25′S, Argentina). These two estuaries are located along the migratory flyway of Neotropical migratory shorebirds, but the Bahia Blanca estuary (area∼110,000 ha) shows a much lower shorebird diversity than Mar Chiquita (area∼4500 ha). The most common species in Bahia Blanca is the two-banded plover C. falklandicus, the species least affected by crabs at Mar Chiquita and which prefers to use high-density crab areas as foraging sites. The oystercatcher Haematopus palliatus was also most abundant in high-density crab areas, but they used these areas for resting. The abundances of preys varied during the study period and between the crab density areas, indicating that the use of these areas by birds is independent of crab density. However, burrowing crabs affect the depth distribution of polychaete and thus their availability to shorebirds. We suggest that this shorebirds–burrowing organism interaction could be generalized for other intertidal estuarine habitats.

Nest-site selection and hatching success of waterbirds in coastal Virginia: some results of habitat manipulation

Abstract Rising sea levels in the mid-Atlantic region pose a long-term threat to marshes and their avian inhabitants. The Gull-billed Tern (Sterna nilotica), Common Tern (S. hirundo), Black Skimmer (Rynchops niger), and American Oystercatcher (Haematopus palliatus), species of concern in Virginia, nest on low shelly perimeters of salt marsh islands on the Eastern Shore of Virginia. Marsh shellpiles are free of mammalian predators, but subject to frequent floods that reduce reproductive success. In an attempt to examine nest-site selection, enhance habitat, and improve hatching success, small (2 × 2 m) plots on five island shellpiles were experimentally elevated, and nest-site selection and hatching success were monitored from 1 May to 1 August, 2002. In addition, location, elevation, and nesting performance of all other nests in the colonies were also monitored. No species selected the elevated experimental plots preferentially over adjacent control plots at any of the sites. When all nests were considere...

Prey abundance and habitat use by migratory shorebirds at coastal stopover sites in Connecticut

Stopover areas are vital for the successful migration of many species of shorebirds, as they, in part, allow individuals to deposit large quantities of fat needed to fuel their northward and southward journeys. While much research has focused on bird migration, few studies closely examine the environmental characteristics of specific stopover areas. For our study, we conducted prey availability surveys and documented shorebird habitat use during northward summer migration for three historically important stopover areas along the Connecticut Long Island Sound coastline in 2000. Coastal Connecticut provides important habitat not only for shorebirds migrating from northern Canada to South America, but also for resident breeding shorebirds (e.g., oystercatchers, plovers, and sandpipers). Our prey availability surveys indicate that all three stopover sites were characterized by some combination of polychaete worms, crustaceans, and mollusks. Polychaete worms of the family Neredidae were the most common prey item at two of the three sites. In addition, the site frequented by the greatest densities of shorebirds also had the greatest density of nereid worms and the greatest diversity of invertebrates. In terms of habitat use, our results indicate that foraging densities tended to be highest on intertidal habitats that were sheltered from coastal wave action and where densities of benthic (burrowing) and epifaunal (surface-dwelling) prey tended to be high. However, some shorebird species, including one breeding resident, the American Oystercatcher (Hae- matopus palliatus) and one migrant, the Ruddy Turnstone (Arenaria interpres), both of special management concern, favored foraging on beach-front habitats. In contrast to foraging habitat preferences, shorebirds roosting at high tidal phases showed strong preferences for beach habitats fronting the Long Island Sound. The use of beach-front habitats for both foraging and roosting poses a challenging situation for beach managers.

Winter Abundance of the American Oystercatcher in South Carolina

Abstract South Carolina winters a large proportion (over 1/3) of the eastern race of the American Oystercatcher (Haematopus palliatus), a declining species. During December of 1999-2002 ground surveys were conducted to provide baseline data on the abundance, age class partitioning and distribution of wintering American Oystercatchers in South Carolina. The number of oystercatchers in South Carolina was stable during this study (3,536, 95% CI: 3,030, 4,042). A single comprehensive survey can estimate the number of oystercatchers with enough precision to detect changes in the population of 13% and greater, but location of flocks and the range of tidal heights needed to concentrate flocks must be known prior to conducting the survey. About 89% of the birds in 2002 roosted on washed shell rakes and 9% had immature bill coloration. Winter surveys of the proportion of immature oystercatchers may provide an index of regional reproductive success, an important parameter for conservation plans. Because South Carol...

Monitoramento de aves limícolas na Salina Diamante Branco, Galinhos, Rio Grande do Norte, Brasil

Monitoring or the s horebirds in Diamante Branco saline, Galinhos, Rio Grand e do Norte, Brazil. Monit orin g of the shorebir ds oflhe Diamante Branco saline located at the municipality of Galinhos, in the coast o f the State o fRio Gra nde do Norte, was initi ated in 1998, with qualitati ve surveys, bird traps using mist net, captured and banding and field observati ons o n the diet of some species. Pa ra mete rs such as constancy were verified, specific diversity was calculated through Pearson correlati on. We regi stered 2 1 species of s horebird s, as fo ll ows: Pluvialis squatarola (Linnaeus , 1758), Charadrius semipalmatus Bonaparte 1825, Arenaria interpres (Li nnaeus, 17 58), Tringaflavipes (Gmelin, 1789), T. melanoleuca (Gmelin , 17 89) a nd AClitis macularia (Linnaeus, 1766). It was observed the reproduction of Charadrius collaris Vieillot, 18 18, C. wilsonia Ord, 18 14 a nd HimanlOpus himanlOpus (Muller, 1776), in the surroundings of lhe saline evaporation tanks. The observation of Calidris himantopus (Bonaparte, 1826) in the evaporation tanks comprised lhe firsl record of the species in Northeastern Brazil. It was ve rified that A. inlerpres, T. .flavipes, T. me/ano/euca and Calidru pusilla (Linnaeus, 1766) feed upon Artemia franciscana (Kell og, 1996) in the first hours ofthe day in lheevaporation tanks. The mean diversity comprised 2 and 3, and the resuJts of equibi lit y s howed thal the species are well dislributed in the samples. A positi ve associati on was registered between Haematopus palliatus Temminck, 1820, C. col/aris, C. wilsonia, and H. himanlopus. These, in turn , associated inversely to A. inlelpres, A. macularia, C. pusilla and C. mimllil/a (Vi eill ot, 18 19), which is possibly due to the fac t that some species are resident, reproducing in lhe locality, with movemenls di sti nct from that specie wich migrate during lhe boreal winter. Traps, surveys, re-traps , and recovers indicale that the Diamante Branco saline comprises na important area for the conservation of the shorebids .

Diet of Sanderling in Buenos Aires Province, Argentina

Abstract The diet of the Sanderling (Calidris alba) was studied using 105 droppings, 34 pellets and direct observations of feeding behavior. This study was carried out during the non-reproductive seasons of 1996 to 2000 in Monte Hermoso, SW of Buenos Aires, Argentina. A total of eleven prey items were identified, with beetles (Coleoptera), Mussels (Brachydontes rodriguezi), clams (Corbula sp.), amphipods (Corophium sp.) and Diptera being the most frequent. The consumption of polychaetes, algae, ants and small fish was also recorded. Sanderlings followed foraging American Oystercatchers (Haematopus palliatus) and cleaned out the valves of mussels and clams (Mesodesma mactroides) left by them. Mussels and beetles were the most constant and dominant prey during the study period. The association of Sanderlings with sandy coasts with rocky patches or restingas is probably due to the rich and diverse invertebrate communities present in this kind of environment, which allow birds to change feeding techniques bet...

Kleptoparasitism by Brown-hooded Gulls and Grey-hooded Gulls on American Oystercatchers

Abstract This study describes qualitatively and quantitatively the kleptoparasitic behavior of the Brown-hooded Gull (Larus maculipennis) and Grey-hooded Gull (Larus cirrocephalus) on the American Oystercatcher (Haematopus palliatus), and considers the influence of environmental variables on the occurrence and success of the kleptoparasitism. Focal and scan samplings were performed, recording a total of 358 kleptoparasitic attempts. The overall occurrence rate was 1.2 ± 1.3 attempts per 5 min., of which 42% of attempts were successful. All kleptoparasitic attempts were performed when oystercatchers were feeding on Stout Razor Clams (Tagellus plebeius). Gulls stole food from Oystercatchers by two kleptoparasitic tactics; running (used in 40% of cases) and flying (used in 60% of cases). A significant difference in the rate of success of kleptoparasitism and an increase in the use of flying kleptoparasitism were observed under windy conditions. Gulls showed limited ability to open clams by themselves, and ne...

The Breeding Status of the American Oystercatcher on the East Coast of North America and Breeding Success in North Carolina

-We studied American Oystercatchers (Haematopus palliatus) by examining reproductive success and the factors affecting it at one location, and by examining the status and trends of breeding population numbers from Florida to Nova Scotia on the east coast of North America. We conducted our field research on Cape Lookout National Seashore, Carteret County, North Carolina from 1997 to 1999, and we documented larger scale breeding population trends by contacting state biologists and reviewing the literature and historical accounts. Presence of eggs and young were checked two to five times per week (by observing from a distance), and efforts were made to determine the reasons for loss of the nest contents. We monitored a total of 245 nests and found low productivity. At least one egg in 32 (13%) nests hatched and one or more chicks fledged from 12 broods. Overall, 14 chicks successfully fledged (nine from North Core Banks and five from South Core Banks) during the three years of the study. Of the 213 clutches that did not hatch, 163 (76%) failed because of predation, and 46 (22%) because of overwash or severe weather. Our minimum estimate for the number of oystercatchers breeding along the entire Atlantic coast and the Gulf coast of Florida is 1,624 pairs. North of Virginia, numbers appear to be stable or slowly increasing and the species has expanded as far north as Cape Sable Island in Nova Scotia. From Virginia south, breeding numbers show a decline in recent years. The number of oystercatchers breeding on barrier islands in Virginia has decreased by more than 50% in the last 20 years. Given their relatively small numbers and inherently low productivity, American Oystercatchers are at risk in rapidly changing coastal ecosystems. Received 1 June 2000, accepted 11 October 2000.

Foraging behavior of the American oystercatcher Haematopus palliatus pitanay (Murphy 1925) on the intertidal ascidian Pyura praeputialis (Heller 1878) in the Bay of Antofagasta, Chile

Oystercatcher foraging behavior has been described for diverse intertidal prey such as limpets, mussels, and oysters. This paper describes foraging behavior of the American oystercatcher, Haematopous palliatus pitanay, on attached and wave-dislodged ascidians, Pyura praeputialis (prey with a restricted geographic range of 70 km) in the Bay of Antofagasta, Chile. Stabbed holes on the top of the ascidian's tunic, probing excursions, handling time, and five prey-handling sequential stages (striking, hammering, prying, cavity food searching, and swallowing) are described and measured. The need to determine ascidian profit-ability for oystercatcher species in Australia and Chile is highlighted.

DISTRIBUTION OF WINTERING SHOREBIRDS IN COASTAL FLORIDA

We used aerial surveys and reports from experienced birders and biologists to identify potentially important sites for wintering shorebirds in coastal Florida. We visited 273 sites in November and December 1993 to assess use by shorebirds and, based on abundance and number of species, we selected the 60 most important sites. We visited these 60 sites at least 3 times between 16 Dec. 1993 and 1 Mar. 1994 and recorded 25 species among an estimated 30,501 shorebirds wintering at the sites. Dunlin (Calidris alpina), Western Sandpipers (C. mauri), Sanderlings (C. alba), and dowitchers (Limnodromus spp.) were the most commonly observed species. Coastal Florida was winter host to >3% of the estimated North American population of Wilson's Plovers (Charadrius wilsonia), Piping Plovers (C. melodus), and American Oystercatchers (Haematopus palliatus). Fifty-three of the 60 most important sites were on Florida's west coast. St. George Sound, Tampa Bay, and Florida Bay contained sites with the highest numbers and most species of shorebirds.

A new species of Sciadiocara Skrjabin, 1916 (Nematoda: Acuariidae) parasitic in shorebirds in Argentina.

In the present paper we describe a new species of the genus Sciadiocara from Haematopus palliatus from the Mar Chiquita coastal lagoon (37 degrees 46' S, 57 degrees 27' W), Argentina. We provide two host records (H. palliatus and Larus dominicanus) for the genus, both from Buenos Aires province, Argentina. S. haematopodi n. sp. closely resembles S. legendrei Petter, 1967. The new species can be distinguished by the morphology of the distal end of the left spicule, the shorter length of the right spicule, the number of pre-anal papillae and the ratio of the length of the vagina vera to the length of the vagina uterina.

Status of the American Oystercatcher, Haematopus palliatus, on the Atlantic Coast

Two recent nesting records for the American oystercatcher, Haematopus palliatus, establish new range limits range for this species along the Atlantic coast. In 1997, one pair of American oystercatchers was observed nesting on Green Island, Maine and another pair was observed in Clark's Harbour on Cape Sable Island, Nova Scotia. Both nests were monitored throughout the breeding season. Two of three chicks that were hatched on Green Island were believed to have fledged. However, the three chicks hatched on Cape Sable Island were believed to have been depredated by gulls nesting on the island. These are the first confirmed breeding records for the American oystercatcher at both of these locations and the nest in Nova Scotia is the first

Shorebird predation may explain the origin of Holocene beds of stout razor clams in life position

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 167:301-306 (1998) - doi:10.3354/meps167301 Shorebird predation may explain the origin of Holocene beds of stout razor clams in life position Oscar Iribarne*, Juan Valero, Mariano M. Martinez, Luis Lucifora, Silvina Bachmann Departamento de Biología (FCEyN), Universidad Nacional de Mar del Plata, CC 573 Correo Central (7600), Mar del Plata, Argentina *E-mail: osiriba@mdp.edu.ar Several hypotheses have been proposed to explain the origin of death assemblages of stout razor clams Tagelus plebeius buried in life position found in Holocene sediments in coastal Argentina and Uruguay: (1) a rapid decrease of sea level, (2) obstruction of the mouth of a coastal lagoon and episodic deposition of fluvial sediments in the mouth of a creek, and (3) a 'taphonomic feedback' process. Hypothesis 1 has been discarded, Hypothesis 2 only has a local explanation, while based on current information Hypothesis 3 is unlikely. A bird predation hypothesis is proposed here on the basis of a study of an extant population. The density of an extant population at the Mar Chiquita coastal lagoon, Argentina (37°46'S, 57°27'W), is higher in the lower intertidal (up to 200 clams m-2) and decreases towards the upper intertidal, and clam size is correlated with burial depth. However, live individuals there coexist with large densities (up to 1500 clams m-2) of dead clams in life position, with densities peaking at the middle-upper intertidal. These shells showed no size-depth of burial correlation. Stout razor clams in fossil deposits (1500 yr BP) also showed large densities of shells in life position (528 clams m-2, SD = 16, n = 20) with no clam size-burial depth relationship. Predation by the American oystercatcher Haematopus palliatus is an important cause of mortality year-round, taking 28 clam h-1 during 3:43 h d-1. Half of the successful attacks left shells in life position buried in the sediment. A computer simulation based on this information showed that predation by 1 oystercatcher produces 9.2 life-position shells m-2 yr-1 (SD = 3.7 life-position shells m-2 yr-1, n = 10000). Thus, 89.5 yr (95% CL = 50-422 yr) are required to generate a mean shell density similar to the one found on our study site (824 clams m-2). Thus, predation by oystercatchers generates a pattern similar to fossil assemblages and is the most likely explanation for the Holocene shell assemblages of the stout razor clams. Intertidal · Predation · Paleoecology · Stout razor clams · Oystercatchers Full text in pdf format PreviousExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 167. Publication date: June 18, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.