Pluvialis Squatarola Research Articles

DYNAMICS OF HABITAT USE BY SHOREBIRDS IN ESTUARINE AND AGRICULTURAL HABITATS IN NORTHWESTERN CALIFORNIA

We examined shorebird use of mudflats, marsh islands, and nearby agricultural fields near Humboldt Bay in northwestern California between September 1988 and April 1989. Most species used fields for both foraging and roosting, including some species usually considered to be mudflat specialists. After seasonal rains began in late fall, Dunlins (Calidris alpina), Least Sandpipers (Calidris minutilla), Long-billed Curlews (Numenius americanus), and Marbled Godwits (Limosa fedoa) became opportunists and used fields at intermediate and high tides when mudflats were inundated. Black-bellied Plovers (Pluvialis squatarola) and Greater Yellowlegs (Tringa melanoleuca) were seasonal generalists during the two wettest seasons, using fields at all tides and mudflats at low and intermediate tides. Western Sandpipers (Calidris mauri) were mudflat specialists, and Willets (Catoptrophorus semipalmatus) were salt marsh opportunists that mainly used mudflats, but shifted to salt marsh at high tide. Killdeer (Charadrius vociferus) and Common Snipe (Gallinago gallinago) were field specialists and did not use the other two habitats in significant densities during any season. The presence of short vegetation and the presence or absence of standing water were the two most important characteristics influencing increased use of fields by all species.

Status of the Nemertea as prey in marine ecosystems

Nemerteans are predators of a wide variety of animals, but little is known of their role as prey for other animals. The presence of toxins in the tissues and secretions of these worms has led to the assumption usually suggested that they are ingested only rarely. However, analysis of a Food Habits Data Base from the United States National Marine Fisheries Service, compiled for fishes collected in the Atlantic Ocean from the Canadian border to Cape Hatteras, North Carolina (1973–1990), showed that nemerteans were recovered from the stomachs of 27 species of fishes in 14 families. They were found in 223 of 26 642 (0.84%) fish stomachs examined in the laboratory, but only in 0.09% of 58 812 fish examined in the field. Among species in the former category, for which ≥1000 were examined, the winter flounder, Pseudopleuronectes americanus(Walbaum), and the yellowtail flounder, Limanda ferruginea (Storer), had the greatest frequency of nemerteans, 71 of 1545 (4.6%) and 33 of 1045 (3.2%), respectively. These nemerteans were identified as Nemertea, Cerebratulus sp. or Micrura sp., but it is likely that they were all of a Cerebratulus-like type. Nemerteans have also been recorded from the guts of eight additional species (including four additional families) of fishes collected from the western Atlantic Ocean, Gulf of Mexico, eastern Pacific Ocean (Washington, Alaska), North Sea and Indian Ocean off South Africa. The black-bellied plover, Pluvialis squatarola(L.), semipalmated plover, Charadrius semipalmatus Bonapart and the herring gull, Larus argentatus Pontoppidan are the only three species known to feed on nemerteans (Cerebratulus lacteus (Leidy) and Paranemertes peregrina Coe by the black-bellied plover and C. lacteus by the other species). Several species of nemerteans are known to ingest other nemerteans, and several arthropods, a squid, and a few other invertebrates also feed on these worms. On the other hand, careful laboratory studies have shown that some members of the Palaeonemertea, Heteronemertea and Hoplonemertea, when fed to various species of fishes, crustaceans (Astacidea, Anomura, Brachyura and Amphipoda) and a polychaete, were rejected, usually violently. There is a history of using large nemerteans, e.g. Cerebratulus lacteus and Polybrachiorhynchus dayi, as bait by sport fishermen in the United States and South Africa. The incongruity of successfuly using these toxic animals to catch fish is discussed in relation to conclusions on the importance of nemerteans as prey in the marine environment.

Organochlorine and mecury concetrations in eggs of grey plovers (Pluvialis squatarola) breeding in the Lena Dlta, north-east Sibveria, 1997

Organochlorine and mecury concetrations in eggs of grey plovers (Pluvialis squatarola) breeding in the Lena Dlta, north-east Sibveria, 1997

SEASONAL ABUNDANCE OF NEARTIC SHOREBIRDS IN THE GULF OF MARANHÃO, BRAZIL

Abstract The seasonal abundance of Neartic shorebirds in the Gulf of Maranhao, Brazil, was studied by censusing three sites from April 1991–March 1992. Censusing was conducted on Cajual Island and Panaquatira Beach at 15-d intervals and at 30-d intervals on Raposa Beach. Bird movements were analyzed by comparing census data from the Gulf of Maranhao with those presented by McNeil (1970) for northeastern Venezuela and by Spaans (1978) for Surinam. During fall migration, there were marked similarities in the abundance peaks of Short-billed Dowitchers (Limnodromus griseus) and Willets (Catoptrophorus semipalmatus) in both Surinam and the Gulf of Maranhao, which might indicate that these species reach these sites by non-stop flight across the Atlantic. Sanderlings (Calidris alba), Semipalmated Plovers (Charadrius semipalmatus), Ruddy Turnstones (Arenaria interpres), Black-bellied Plovers (Pluvialis squatarola), Semipalmated Sandpipers (Calidris pusilla), and Whimbrels (Numenius phaeopus) reached their fall pe...

Influence of rodent density on nesting associations involving the Bar‐tailed Godwit Limosa lapponica

The Bar‐tailed Godwit Limosa lapponica rarely defends its nest aggressively against predators, but rather associates with other more aggressive species for protection. I studied the distribution of Bar‐tailed Godwit nests relative to nests of the aggressive Longtailed Skua Stercorarius longicaudus, as well as to nests of two slightly less aggressive alternative ‘protective umbrella’ species, the Whimbrel Numenius phaeopus and the Grey Plover Pluvialis squatarola. Rodents are the main prey of the Long‐tailed Skua but, in years when numbers of rodents are low, Long‐tailed Skuas also eat eggs and chicks of other birds. Data on rodent densities and nest distribution were collected on Finnmarksvidda, Northern Norway, in 1987, 1989, 1990, 1992 and 1997, and on Taimyr, Siberia, in 1994 and 1995. It is concluded that the Bar‐tailed Godwit is able to evaluate the probability of nest predation from Long‐tailed Skuas, based on direct or indirect information about the status of local rodent populations. This information is used to choose between Long‐tailed Skuas and other potential species for protection against nest predators.

Primary moult, biometrics, mass and age composition of Grey Plovers Pluvialis squatarola in southeastern India

Little is known about the biology of waders wintering in southern Asia; this paper deals with the Grey Plover Pluvialis squatarola, a species extensively studied only in western Europe. Adult Grey Plovers wintering in southeastern India underwent primary moult in autumn; the duration was estimated to be 127 days, with mean starting date 1 September and mean completion date 5 January. Some first-year Grey Plovers initiated primary moult in late winter and spring, and completed this moult the following spring. The average mass of adults on arrival in September was 200 g, fluctuated close to 220 g from October to February, and increased to 280 g near the end of May. The mass variation did not show the January peak observed in western Europe. Breeding productivity, measured as the percentage of first-year birds in winter catches, varied between 5% and 70% over six years, and showed a positive correlation with that of Dark-bellied Brent Geese Branta b. bernicla in western Europe and Curlew Sandpipers Calidris ferruginea in South Africa.

Organochlorine and mercury concentrations in eggs of grey plovers (Pluviulis squuturola) breeding in the Lena Delta, north-east Siberia, 1997

Seven eggs from four clutches of grey plovers (Pluvialis squatarola) breeding in the Lena Delta, Sakha Republic, Yakutia, in 1997 were analysed for persistent organochlorines and mercury. Contamination levels were low and within the same range as found in eggs from waders (Charadriiformes) breeding in north-west Europe. One exception was ?HCH, averaging 99.2 ng g?1 fresh egg mass, a level about ten times higher than in wader eggs from north-west Europe. ?-HCH accounted for 98% of the total HCH concentration. There are indications that the pesticide levels may reflect former local use. ?PCB level (57.0 ng g?1, 62 congeners) and mercury concentration (68.7 ng g?1) can be considered low.

Abundance and distribution of waterbirds on the Knysna Estuary

Twelve waterbird counts were undertaken on the Knysna Estuary during January (summer) and July (winter) from 1993 to 1998. A total of 67 species were recorded; a median of 5343 waterbirds were present during summer, 76% of them Palearctic migrants, dropping to a median of 2336 waterbirds in winter. Waterbird numbers were about a third lower than normal during January 1997 following a flood in November 1996. There was a shift from a summer avifauna comprised predominantly of invertebrate-feeding migrant waders to a winter avifauna comprised mainly of piscivorous species. During the summer, 52% of the birds were Curlew Sandpipers and Grey Plovers, Greenshanks, Kelp Gulls and Whimbrels each made up more than 6% of the avifauna. During the winter Kelp Gulls, Cape and Reed Cormorants, Little Egrets and Sacred Ibises together comprised 62% of the avifauna. The majority of invertebrate-feeding birds were found on the intertidal mudbanks around the Ashmead Channel and on the Brenton side of the estuary below the rail bridge, whereas the shallow water areas between the rail and N2 bridges were important to piscivorous birds, especially during the winter. The Knysna Estuary, being the largest estuarine system in the warm temperate region of South Africa, supports the largest number of birds of any estuarine system between Cape Agulhas and Durban Bay. However, bird densities are not as high as on other important bird estuaries and it is hypothesised that this may be due to recreational disturbance and to the relatively low density and availability of macrobenthic invertebrates.

Birds and Mammals of the Lena Delta Nature Reserve, Siberia

The Lena Delta is the largest arctic delta covered entirely by tundra. Protected since 1986, it is one of the richest areas in the Arctic north of 71° N for both species diversity and breeding densities. Between 6 June and 17 August 1997, 16 mammal species and 76 bird species were recorded in the Lena Delta Nature Reserve and the surrounding buffer zone. Several species are new to the region: far-eastern curlew, fieldfare, redwing, arctic warbler, red-breasted flycatcher, and common rat. New breeders are merlin and arctic warbler. These 1997 records, combined with those from earlier studies, give a total of 122 bird species for the region. Of these, 67 have been found breeding at least once. Densities ranging from 245 to 641 birds per km² were recorded in two restricted study areas. Such densities are unusually high north of 70° N for non-colonial breeding birds. Lapland longspur (100-300 individuals/km²), red phalarope (up to 200 ind./km²), and several Calidris species were the most common. Ruddy turnstone and dunlin had densities higher than those previously reported from the Lena Delta and other Siberian sites. Among the shorebirds, spotted redshank, pintail snipe, grey plover, dunlin, and curlew sandpiper may have extended their breeding range or increased in population during the last 15 years. But further evidence is still needed to confirm the westward extension of spectacled eider, long-billed dowitcher, and sharp-tailed sandpiper.

Tundra plovers: the Eurasian, Pacific and American golden plovers and grey plover

Tundra plovers: the Eurasian, Pacific and American golden plovers and grey plover

Sediment ingestion of two sympatric shorebird species

Black-bellied plovers ( Pluvialis squatarola) have short bills and primarily peck while foraging whereas Willets ( Catoptrophorus semipalmatus) have long bills and primarily probe with bills open in sediments. Intestinal digesta were collected from these species at sympatric overwintering sites in southern California near San Diego to relate sediment ingestion to bill length and feeding behavior. Plover digesta contained an estimated 29% sediment, and Willet digesta an estimated 3% sediment. Techniques based on acid insoluble ash and on the elemental markers of Al, Fe, and Ti in digesta provided similar results. High Ca concentrations in Willet digesta along with our observations suggested that the Willets in our sample fed primarily on molluscs and crustaceans. Sediment ingestion may be species-specific, not necessarily linked to bill length or probing behaviors, and may greatly affect a bird's exposure to environmental contaminants in sediment.

Metal and Trace Element Burdens in Two Shorebird Species at Two Sympatric Wintering Sites in Southern California.

In January and November, 1994, ten willets (Catoptrophorus semipalmatus) and ten black-bellied plovers (Pluvialis squatarola) were collected at a south-facing sandy beach at the North Island Naval Air Station (NASNI) and ten willets and three plovers were collected at the Tijuana Slough National Wildlife Refuge (TSNWR), 16 km to the southeast. Concentrations of 19 inorganic analytes were determined in the livers. Differences between sexes in diet or abilities to retain some analytes are indicated because male willets tend to have greater levels of Cd than females and male plovers tend to have greater levels of Fe, Hg, and Mn than females. Concentrations of Hg and Mg in willets decreased from January to November. If this decrease is a part of an annual cycle, then the birds may be acquiring those elements while at NASNI. The differences between sites shows higher levels of As and Se but lower levels of Mn in willets at NASNI while plovers have lower levels of Cu, Mg and Zn at NASNI. There were no correlations between Hg and Se concentrations in the livers of any sample group of birds.

Optimal Choice of Neighbour: Predator Protection among Tundra Birds

The distribution of breeding birds on Siberian tundra was studied around nests of Long-tailed Skuas Stercorarius skua, Grey Plovers Pluvialis squatarola, Pacific Golden Plovers Pluvialisfulva and Bar-tailed Godwits Limosa lapponica, all of which have been observed attacking avian predators entering their nesting territories. Only the skua and the Grey Plover turned out to do so regularly, however. The efficiency of defence was measured using artificial nests 30, 70 and 150 m from nests of the four species. The survival of nests was significantly higher than the survival of control group nests only around Grey Plover nests. Long-tailed Skuas defended their own nests fiercely, but were observed preying on artificial nests inside their territories. Nest distribution of local birds around the potential protectors reflected the efficiency with which the protectors defended their territory, but most of all it reflected the survival probabilities found for artificial nests: the number of nests located within 100 m from Grey Plover nests was significantly higher than in control plots. The Long-tailed Skua did not attract more birds than control points, presumably because it could not be trusted as a reliable neighbour when rodent numbers were decreasing. It is concluded that tundra birds are able to make optimal decisions about the choice of protective neighbour.

Environmental and Habitat Correlates of Pasture Use by Nonbreeding Shorebirds

Throughout coastal regions of the world, pasturelands often augment important and declining intertidal foraging habitats for nonbreeding shorebirds (Suborder Charadrii). Little is known, however, about factors influencing bird use of pastures. Hence, we examined the spatial distribution of shorebirds in coastal pastures near Humboldt Bay, California from October 1991-May 1992 and correlated spatial distribution patterns with environmental and habitat variables. Shorebirds used pastures in a nonrandom (clumped) fashion. Pasture use varied seasonally for Killdeer (Charadrius vociferus), Marbled Godwit (Limosa fedoa), and Common Snipe (Gallinago gallinago); Dunlin (Calidris alpina) and Black-bellied Plover (Pluvialis squatarola) use increased when it rained, and Dunlin, Black-bellied Plover, and Killdeer use increased nearer the time of a new moon. At the level of the individual pasture, the likelihood of encountering most species (5 of 6) increased as vegetation height decreased. The likelihood of pasture use by Dunlin and Killdeer increased when shorebirds used pastures the previous week. Extensive, nonrandom use of coastal pastures by nonbreeding shorebirds indicates that conservation planning for shorebirds should consider habitat characteristics. In the vicinity of Humboldt Bay and other coastal bays, use of pastures by shorebirds can be increased by practices that provide short vegetation. Although shorebird use did not correlate with use of pastures by cattle, grazing by livestock is probably the means by which to achieve habitat characteristics attractive to shorebirds while maintaining compatible human uses on private lands. Regular use of some pastures by shorebirds indicates that site faithfulness may be important and that "traditional" sites need to be identified and protected.

Adaptive variation in the foraging behaviour of Grey Plover Pluvialis squatarola and Whimbrel Numenius phaeopus

Between‐site variation in the diet and foraging behaviour of a fixed‐method forager, the Grey Plover Pluvialis squatarola, and a versatile forager, the Whimbrel Numenius phaeopus, was examined and compared at nine tropical and south temperate sites. Grey Plover always foraged in a run‐stop‐search manner but changed the emphasis of components of this behaviour in response to prey type. Whimbrel foraged tactilely or visually and readily changed foraging speed and habitat. Both species ate a variety of prey species depending on their availability. The diet of Grey Plover was dominated by small prey, polychaetes and crabs, and Whimbrel ate mostly crabs, with Whimbrel being the more specialized in prey choice. The broader diversity of prey types consumed by Grey Plover was attributed to limitations imposed by obligate visual foraging, whereas the flexible foraging behaviour of Whimbrel allowed the latter to concentrate their efforts on the most profitable prey. Grey Plover appeared to have a density upper limit, determined by their stereotyped foraging behaviour. Whimbrel densities varied greatly in response to prey type and foraging method. Foraging effort could not be predicted from measurements of instantaneous daytime energy intake rates, and reasons for the lack of this relationship are discussed.

The diet of wintering waders in Cádiz Bay, southwest Spain

In Cádiz Bay, southwest Spain, salt pans and fish ponds in the saltmarshes provide an important additional source of food to intertidal flats for many waders (Charadrii) during the winter. As little is known about the diet of waders in Spain in general, and in saline ponds in particular, droppings and pellets produced by waders were collected from the ponds and mudflats, and analysed for the remains of prey. Direct observations of feeding birds were also made. The diets of Redshank Tringa totanus, Grey Plover Pluvialis squatarola, Curlew Numenius arquata, Black–tailed Godwit Limosa limosa, Bar–tailed Godwit Limosa lapponica, Ringed Plover Charadrius hiaticula, Kentish Plover Charadrius alexandrinus, Black–winged Stilt Himantopus himantopus, Dunlin Calidris alpina, Little Stint Calidris minuta and Sanderling Calidris alba were investigated in this way, with particular attention being paid to the saline ponds. Compared with the results from studies made in the winter in northern Europe, many of the waders in the Bay took many insects and, surprisingly, also the seeds of saltmarsh plants.

Quantification of Microscopic Feather Characters Used in the Identification of North American Plovers

Variation in microscopic characters of plumulaceous barbs of six species of Charadrius was studied to quantify characters and test differences among taxa. Pluvialis squatarola was used for intergeneric comparisons. Intraspecific variation in feathers from the sternopectoral tract of C. vociferus was examined to define character parameters and to determine within-vane variation and vane symmetry. A significant difference was observed among the barbs of four regions within each vane of the same feather, but barbs from opposing vanes were not significantly different from one another. Interspecific variation then was studied using discriminant function analysis. Pluvialis separated from all species of Charadrius. Two subgroups were apparent within Charadrius: semipalmatus, vociferus and montanus separated from wilsonia, alexandrinus and melodus.

Short-term Effects of Intertidal Macroalgal Blooms on the Macrohabitat Selection and Feeding Behaviour of Wading Birds in the Mondego Estuary (West Portugal)

The possible effects of intertidal macroalgal blooms on the feeding distribution and behaviour of the waders in the Mondego Estuary (West Portugal) are discussed in the present paper. The presence of algae over the sediments did not deter the waders absolutely from feeding in a place, but most species did show some tendency to avoid highly eutrophic areas. However, there were no clear signs that the species redistributed themselves within the Estuary as the amount of algae changed, nor did the alternative feeding habitats (the salt pans) seem to be used more when algae were particularly abundant on the mud flats. In one species, bird numbers, rather than the amount of algae present, explained the numbers of birds using the salt pans when the two factors were considered together in a multiple regression analysis. There were no striking differences between algae-free and algae-weeded areas in some aspects of the foraging of two representative species, the scolopacid Dunlin Calidris alpinaand the charadriid Grey Plover Pluvialis squatarola. The results suggest either: (1) that the presence of algae did not strongly influence the distribution of the feeding waders, at least in the conditions prevailing during the study; or (2) that most waders were able to adapt to feeding on weeded areas; perhaps through subtle and undetected alterations in their feeding behaviour.

A Guide to the Provision of Refuges for Waders: An Analysis of 30 Years of Ringing Data from the Wash, England

1. It has been proposed to establish roost refuges to limit the disturbance to internationally important over-wintering populations of waders on the Wash. 2. Waders have been caught regularly on the Wash since 1959. By 1993, 24 576 oystercatchers, 4125 grey plovers, 38 041 knots, 96 801 dunlins and 11 729 redshanks had been ringed at 85 roost sites around the Wash. 3. Analysis of the movements between roosts provides a means of determining the relative mobility of waders and the effect of spacing on the availability of the proposed refuges to waders during normal roost movements. This analysis does not take into account either movements between feeding sites nor between roosting and feeding sites. 4. The Wash was divided into five sections according to observed wader movements between roosts and feeding grounds. At least 79% of inter-roost movements of oystercatchers, grey plovers, knots, dunlins and redshanks within a year were restricted to a single section. Juvenile waders changed section more frequently than adults. Waders were almost as site faithful between-year as within-year. 5. A model, based on the variation in retrap rate with distance of the three least mobile wader species within a section of the Wash, was used to describe wader dispersal between roosts. The model was then used to estimate the effect of interrefuge distance on the proportion of waders reaching at least one refuge during normal roost movements. 6. Between roosts waders dispersed over short distances within a section of the Wash. Placing refuges 2, 4 and 7 km apart for grey plovers, 2.5, 5 and 10 km apart for dunlins within-year, and 3.5, 5.5 and 9.5 km apart for redshanks put the refuges within reach of 90, 75 and 50% of the respective populations of these species during their normal roost movements. To validate the sectional approach, the analysis was repeated using roosting movements of dunlins over another section and over the whole Wash; the results were similar to those obtained in the original analysis. 7. The implications of wader dispersal for refuge creation are discussed.

Seasonal Variation in Diurnal and Nocturnal Distributions of Nonbreeding Shorebirds at North Humboldt Bay, California

Recent studies of nocturnal foraging by shorebirds (Charadriiformes: Charadrii) suggest that many species feed at night. Much of this research has been qualitative and/or restricted to a small portion of the annual cycle (e.g., a few nights or one season) making it difficult to evaluate the extent to which nocturnal foraging varies seasonally. Consequently, we examined seasonal variation in abundance and distribution of diurnal and nocturnal foraging shorebirds from 10 Jan 1992-10 Jan 1993 at North Humboldt Bay, California. Shorebirds foraged primarily during the day. Overall, day/night frequency of occurrence (percent of censuses with birds) was 87%/48%. In fall, frequency of occurrence of shorebirds differed less between day and night (day/night: 82%/64%) than during spring (day/night: 79%/14%) or winter (day/night: 100%/42%). Moreover, nocturnal abundance of Marbled Godwit (Limosa fedoa), Willet (Catoptrophorus semipalmatus), dowitchers (Limnodromus scolopaceus and L. griseus), and Black-bellied Plover (Pluvialis squatarola) peaked in fall, whereas diurnal abundance of these species peaked in winter (Marbled Godwit, Black-bellied Plover, and dowitchers) or spring (Willet). Taxa varied in day/night patterns. For Scolopacids, diurnal abundance significantly exceeded nocturnal abundance. However, abundance of American Avocet (Recurvirostra americana), Black-bellied Plover, and Semipalmated Plover (Charadrius semipalmatus) did not differ significantly between day and night. Our results suggest that a researcher's choice of season or taxa may influence observed patterns of diurnal and nocturnal distributions of shorebirds considerably.