Post by Eaglehawk on Oct 30, 2019 7:13:27 GMT
Sanderling - Charadrius calidris
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes
Family: Scolopacidae
Genus: Calidris
Species: Calidris alba (Pallas, 1764)
The sanderling (Calidris alba) is a small wading bird. The name derives from Old English sand-yrðling, "sand-ploughman". The genus name is from Ancient Greek kalidris or skalidris, a term used by Aristotle for some grey-coloured waterside birds. The specific alba is Latin for "white".
It is a circumpolar Arctic breeder, and is a long-distance migrant, wintering south to South America, South Europe, Africa, and Australia. It is highly gregarious in winter, sometimes forming large flocks on coastal mudflats or sandy beaches.
It is somewhat unlike other sandpipers in appearance, which has led to the suggestion that it should be placed into a monotypic genus Crocethia. A more recent review (Thomas et al., 2004) indicates, however, that the sanderling is a fairly typical "stint" or small sandpiper and should be separated from the large knots with its closest relatives in a distinct genus.
This bird is similar in size to a dunlin, but stouter, with a thick bill. It shows a strong white wingbar in flight, and runs along the sandy beaches it prefers with a characteristic "bicycling" action of its legs, stopping frequently to pick small food items. It eats small crabs and other small invertebrates. In spring, birds migrating north from South America consume large numbers of horseshoe crab eggs in the Delaware Bay area.
In spring, the birds arrive on the High Arctic breeding grounds (see map), where they lay 3–4 eggs in a ground scrape. On the nesting grounds, these birds mainly eat insects and some plant material.
The sanderling was described by the German naturalist Peter Simon Pallas in 1764 and given the binomial name Trynga alba.
The sanderling is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.
Description
The sanderling is a small plump sandpiper, 18–20 cm (7.1–7.9 in) in length. Its weight ranges from 40–100 g (1.4–3.5 oz). The winter bird is very pale, almost white apart from a dark shoulder patch. This is the source of the specific name, alba, which is the Latin for "white". Later in the summer, the face and throat become brick-red. The juvenile bird is spangled black and white, and shows much more contrast than the adult.
If its size is misjudged, a sanderling in breeding plumage can be mistaken for some varieties of stint, or a sanderling in winter plumage can be mistaken for a dunlin or red knot. It can be told from other small wading birds, given good views, by its lack of a hind toe. Its behavior is also distinctive.
Distribution, habitat and migration
The sanderling breeds in the High Arctic areas of North America, Europe and Asia. In North America, it breeds in the Canadian Arctic Archipelago, Nunavut, Greenland (and to a lesser extent Alaska). In Eurasia, it breeds in Spitsbergen and areas of northern Russia from the Taymyr Peninsula to the New Siberian Islands. In the northern winter, it has a nearly cosmopolitan distribution across the world's marine coasts. It is a complete migrant, travelling between 3,000 to 10,000 km (1,900 to 6,200 mi) from its breeding grounds to its wintering sites. Birds that travel further also arrive later and leave sooner. Most adults leave the breeding grounds in July and early August, whereas juvenile birds leave in late August and early September. The northward migration begins in March at the southern end of their winter distribution.
The breeding habitat of the sanderling is coastal tundra north of 5 °C (41 °F) July isotherm. The species typically chooses nesting sites on dry stony areas near wet areas, from 60 m (200 ft) above sea level to 800 m (2,600 ft). During the winter and its migration, it is most commonly found on coastal sandy beaches, but also occurs on tidal sand flats, mud flats and the shores of lakes and rivers. More infrequently, it may occur on rocky shores.
Subspecies
The sanderling consists of two subspecies:
C. a. alba, (Pallas, 1764), breeds on Ellesmere Island, north & east Greenland, Svalbard, Franz Josef Land and the Taymyr Peninsula
C. a. rubida, (Gmelin, 1789), breeds in northeast Siberia, Alaska and northern Canada
Behaviour
Sanderlings feed on invertebrate prey buried in the sand in the upper intertidal zone. In North America, this diet largely consists of the isopods Excirolana linguifrons, Excirolana kincaidii, and the mole crab, Emerita analoga. When the tide is out, these crustaceans live in burrows some way beneath the surface. When the tide comes in, they move into the upper layers of sand and feed on the plankton and detritus that washes over them with each wave. They then burrow rapidly down again as the water retreats. They leave no marks on the surface, so the sanderlings hunt for them by plunging their beaks into the sand at random, consuming whatever they find. Their bills can penetrate only 2 or 3 cm (0.79 or 1.18 in) and as the water swirls around and retreats, the sand is softer; this makes it easier for the birds' beaks to penetrate further. In the spring, when much breeding activity is taking place in the benthic community, there may be as many as 4000 invertebrates per square metre, but their average size is smaller than later in the year. The birds appear to rush madly around at the edge of the surf, but in reality they are maximising their chances of catching as many prey animals as possible when they are at their most vulnerable near the surface.
Breeding behaviour
At breeding time sanderlings are territorial, with the male aggressively defending its territory. They may either form monogamous pairs or polyandrous (one female and two male) pairings.
Migratory birds are worse off in West Africa
by University of Groningen
A flying sanderling during spring migration in Iceland. Credit: Jeroen Reneerkens
Migratory sandpipers breeding in Greenland who choose to spend the winter in West Africa instead of elsewhere along the East Atlantic coast have a lower chance of survival, are more likely to skip their first breeding season and arrive later at their breeding grounds. An article in the Journal of Animal Ecology, spearheaded by researcher Jeroen Reneerkens (University of Groningen and the Royal Netherlands Institute for Sea Research, NIOZ), challenges the widely held idea that the costs of longer migratory flights are inevitably offset by benefits in the winter habitats.
Sanderling
The sanderling is a small migratory shorebird that breeds on the high arctic tundra. In late summer, it migrates to beaches in tropical or temperate regions. Beach visitors may know them as the grey-white birds that run back and forth in front of the waves. Their annual migratory flights vary between 3,700 and 22,000 km. When Greenlandic sanderlings are a few months old, they choose a winter habitat in a coastal area somewhere between Scotland and Namibia, such as the Wadden Sea Islands. They remain faithful to that location for the rest of their lives, only interrupted by long annual flights to Greenland to breed.
Wintering habitats
An international research team, led by Dr. Jeroen Reneerkens of the University of Groningen and NIOZ, wondered why one sanderling may choose to stay in the United Kingdom for the winter, while another from the same breeding population migrates all the way to Namibia. For seven years, they studied the pros and cons of spending the winter in several locations in Europe and Africa. The team used color-rings to individually tag thousands of birds, which were then observed and reported by a large international network of birdwatchers. This allowed the researchers to accurately estimate both the survival probabilities and the timing of migration.
Sanderlings have been tagged with color-rings to make them individually identifiable. The study is based on tens of thousands of observations of such tagged birds. Credit: Jeroen Reneerkens
Poor conditions
Sanderlings wintering in West Africa were worse off compared to sanderlings wintering in Europe or further south in Africa. The research undermines a widely held idea among biologists, namely that favorable conditions in the winter habitat make up for the long, arduous flights. The researchers suspect that little and/or low-quality food just before leaving the tropical wintering habitat may explain why sanderlings in West Africa are more likely to die young, arrive late at the breeding grounds and young birds are more likely to spend their first summer in tropical Africa and thus skip their first possible breeding opportunity.
Sanderlings breed on Greenland but spend the winter along European or African coasts. Credit: Jeroen Reneerkens
Non-stop flying
Reneerkens says, "During migration, sanderlings from West Africa may be more likely to run out of fuel, or they may be forced to make an extra landing causing delays. Sanderlings from Namibia, on the other hand, fly across Africa in one go in the spring, which is more than 6,000 km. Yet, this has no impact on their survival or timing of migration. They can only do this if there is enough food in Namibia to fuel up. At the same time, it also suggests that birds actively avoid West Africa in the spring, possibly because there is too little food."
These results raise new questions. "For example, to what extent can the Wadden Sea compensate for the migratory problems of sanderlings wintering in tropical West Africa?" says Reneerkens.
phys.org/news/2019-10-migratory-birds-worse-west-africa.html
Journnal Reference:
Jeroen Reneerkens et al, Low fitness at low latitudes: Wintering in the tropics increases migratory delays and mortality rates in an Arctic breeding shorebird, Journal of Animal Ecology (2019). DOI: 10.1111/1365-2656.13118
Abstract
Evolutionary theories of seasonal migration generally assume that the costs of longer migrations are balanced by benefits at the non‐breeding destinations.
We tested, and rejected, the null hypothesis of equal survival and timing of spring migration for High Arctic breeding sanderling Calidris alba using six and eight winter destinations between 55°N and 25°S, respectively.
Annual apparent survival was considerably lower for adult birds wintering in tropical West Africa (Mauritania: 0.74 and Ghana: 0.75) than in three European sites (0.84, 0.84 and 0.87) and in subtropical Namibia (0.85). Moreover, compared with adults, second calendar‐year sanderlings in the tropics, but not in Europe, often refrained from migrating north during the first possible breeding season. During northward migration, tropical‐wintering sanderlings occurred at their final staging site in Iceland 5–15 days later than birds wintering further north or south. Namibia‐wintering sanderlings tracked with solar geolocators only staged in West Africa during southward migration.
The low annual survival, the later age of first northward migration and the later passage through Iceland during northward migration of tropical‐wintering sanderlings, in addition to the skipping of this area during northward but not southward migration by Namibia‐wintering sanderlings, all suggest they face issues during the late non‐breeding season in West Africa.
Migrating sanderlings defy long distances but may end up in winter areas with poor fitness prospects. We suggest that ecological conditions in tropical West Africa make the fuelling prior to northward departure problematic.
besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2656.13118
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes
Family: Scolopacidae
Genus: Calidris
Species: Calidris alba (Pallas, 1764)
The sanderling (Calidris alba) is a small wading bird. The name derives from Old English sand-yrðling, "sand-ploughman". The genus name is from Ancient Greek kalidris or skalidris, a term used by Aristotle for some grey-coloured waterside birds. The specific alba is Latin for "white".
It is a circumpolar Arctic breeder, and is a long-distance migrant, wintering south to South America, South Europe, Africa, and Australia. It is highly gregarious in winter, sometimes forming large flocks on coastal mudflats or sandy beaches.
It is somewhat unlike other sandpipers in appearance, which has led to the suggestion that it should be placed into a monotypic genus Crocethia. A more recent review (Thomas et al., 2004) indicates, however, that the sanderling is a fairly typical "stint" or small sandpiper and should be separated from the large knots with its closest relatives in a distinct genus.
This bird is similar in size to a dunlin, but stouter, with a thick bill. It shows a strong white wingbar in flight, and runs along the sandy beaches it prefers with a characteristic "bicycling" action of its legs, stopping frequently to pick small food items. It eats small crabs and other small invertebrates. In spring, birds migrating north from South America consume large numbers of horseshoe crab eggs in the Delaware Bay area.
In spring, the birds arrive on the High Arctic breeding grounds (see map), where they lay 3–4 eggs in a ground scrape. On the nesting grounds, these birds mainly eat insects and some plant material.
The sanderling was described by the German naturalist Peter Simon Pallas in 1764 and given the binomial name Trynga alba.
The sanderling is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.
Description
The sanderling is a small plump sandpiper, 18–20 cm (7.1–7.9 in) in length. Its weight ranges from 40–100 g (1.4–3.5 oz). The winter bird is very pale, almost white apart from a dark shoulder patch. This is the source of the specific name, alba, which is the Latin for "white". Later in the summer, the face and throat become brick-red. The juvenile bird is spangled black and white, and shows much more contrast than the adult.
If its size is misjudged, a sanderling in breeding plumage can be mistaken for some varieties of stint, or a sanderling in winter plumage can be mistaken for a dunlin or red knot. It can be told from other small wading birds, given good views, by its lack of a hind toe. Its behavior is also distinctive.
| Standard Measurements | |
|---|---|
| length | 180–220 mm (7.1–8.7 in) |
| weight | 60 g (2.1 oz) |
| wingspan | 430 mm (17 in) |
| wing | 114.5–121.6 mm (4.51–4.79 in) |
| tail | 47.3–53 mm (1.86–2.09 in) |
| culmen | 22.5–26.6 mm (0.89–1.05 in) |
| tarsus | 23.5–25.8 mm (0.93–1.02 in) |
Distribution, habitat and migration
The sanderling breeds in the High Arctic areas of North America, Europe and Asia. In North America, it breeds in the Canadian Arctic Archipelago, Nunavut, Greenland (and to a lesser extent Alaska). In Eurasia, it breeds in Spitsbergen and areas of northern Russia from the Taymyr Peninsula to the New Siberian Islands. In the northern winter, it has a nearly cosmopolitan distribution across the world's marine coasts. It is a complete migrant, travelling between 3,000 to 10,000 km (1,900 to 6,200 mi) from its breeding grounds to its wintering sites. Birds that travel further also arrive later and leave sooner. Most adults leave the breeding grounds in July and early August, whereas juvenile birds leave in late August and early September. The northward migration begins in March at the southern end of their winter distribution.
The breeding habitat of the sanderling is coastal tundra north of 5 °C (41 °F) July isotherm. The species typically chooses nesting sites on dry stony areas near wet areas, from 60 m (200 ft) above sea level to 800 m (2,600 ft). During the winter and its migration, it is most commonly found on coastal sandy beaches, but also occurs on tidal sand flats, mud flats and the shores of lakes and rivers. More infrequently, it may occur on rocky shores.
Subspecies
The sanderling consists of two subspecies:
C. a. alba, (Pallas, 1764), breeds on Ellesmere Island, north & east Greenland, Svalbard, Franz Josef Land and the Taymyr Peninsula
C. a. rubida, (Gmelin, 1789), breeds in northeast Siberia, Alaska and northern Canada
Behaviour
Sanderlings feed on invertebrate prey buried in the sand in the upper intertidal zone. In North America, this diet largely consists of the isopods Excirolana linguifrons, Excirolana kincaidii, and the mole crab, Emerita analoga. When the tide is out, these crustaceans live in burrows some way beneath the surface. When the tide comes in, they move into the upper layers of sand and feed on the plankton and detritus that washes over them with each wave. They then burrow rapidly down again as the water retreats. They leave no marks on the surface, so the sanderlings hunt for them by plunging their beaks into the sand at random, consuming whatever they find. Their bills can penetrate only 2 or 3 cm (0.79 or 1.18 in) and as the water swirls around and retreats, the sand is softer; this makes it easier for the birds' beaks to penetrate further. In the spring, when much breeding activity is taking place in the benthic community, there may be as many as 4000 invertebrates per square metre, but their average size is smaller than later in the year. The birds appear to rush madly around at the edge of the surf, but in reality they are maximising their chances of catching as many prey animals as possible when they are at their most vulnerable near the surface.
Breeding behaviour
At breeding time sanderlings are territorial, with the male aggressively defending its territory. They may either form monogamous pairs or polyandrous (one female and two male) pairings.
Migratory birds are worse off in West Africa
by University of Groningen
A flying sanderling during spring migration in Iceland. Credit: Jeroen Reneerkens
Migratory sandpipers breeding in Greenland who choose to spend the winter in West Africa instead of elsewhere along the East Atlantic coast have a lower chance of survival, are more likely to skip their first breeding season and arrive later at their breeding grounds. An article in the Journal of Animal Ecology, spearheaded by researcher Jeroen Reneerkens (University of Groningen and the Royal Netherlands Institute for Sea Research, NIOZ), challenges the widely held idea that the costs of longer migratory flights are inevitably offset by benefits in the winter habitats.
Sanderling
The sanderling is a small migratory shorebird that breeds on the high arctic tundra. In late summer, it migrates to beaches in tropical or temperate regions. Beach visitors may know them as the grey-white birds that run back and forth in front of the waves. Their annual migratory flights vary between 3,700 and 22,000 km. When Greenlandic sanderlings are a few months old, they choose a winter habitat in a coastal area somewhere between Scotland and Namibia, such as the Wadden Sea Islands. They remain faithful to that location for the rest of their lives, only interrupted by long annual flights to Greenland to breed.
Wintering habitats
An international research team, led by Dr. Jeroen Reneerkens of the University of Groningen and NIOZ, wondered why one sanderling may choose to stay in the United Kingdom for the winter, while another from the same breeding population migrates all the way to Namibia. For seven years, they studied the pros and cons of spending the winter in several locations in Europe and Africa. The team used color-rings to individually tag thousands of birds, which were then observed and reported by a large international network of birdwatchers. This allowed the researchers to accurately estimate both the survival probabilities and the timing of migration.
Sanderlings have been tagged with color-rings to make them individually identifiable. The study is based on tens of thousands of observations of such tagged birds. Credit: Jeroen Reneerkens
Poor conditions
Sanderlings wintering in West Africa were worse off compared to sanderlings wintering in Europe or further south in Africa. The research undermines a widely held idea among biologists, namely that favorable conditions in the winter habitat make up for the long, arduous flights. The researchers suspect that little and/or low-quality food just before leaving the tropical wintering habitat may explain why sanderlings in West Africa are more likely to die young, arrive late at the breeding grounds and young birds are more likely to spend their first summer in tropical Africa and thus skip their first possible breeding opportunity.
Sanderlings breed on Greenland but spend the winter along European or African coasts. Credit: Jeroen Reneerkens
Non-stop flying
Reneerkens says, "During migration, sanderlings from West Africa may be more likely to run out of fuel, or they may be forced to make an extra landing causing delays. Sanderlings from Namibia, on the other hand, fly across Africa in one go in the spring, which is more than 6,000 km. Yet, this has no impact on their survival or timing of migration. They can only do this if there is enough food in Namibia to fuel up. At the same time, it also suggests that birds actively avoid West Africa in the spring, possibly because there is too little food."
These results raise new questions. "For example, to what extent can the Wadden Sea compensate for the migratory problems of sanderlings wintering in tropical West Africa?" says Reneerkens.
phys.org/news/2019-10-migratory-birds-worse-west-africa.html
Journnal Reference:
Jeroen Reneerkens et al, Low fitness at low latitudes: Wintering in the tropics increases migratory delays and mortality rates in an Arctic breeding shorebird, Journal of Animal Ecology (2019). DOI: 10.1111/1365-2656.13118
Abstract
Evolutionary theories of seasonal migration generally assume that the costs of longer migrations are balanced by benefits at the non‐breeding destinations.
We tested, and rejected, the null hypothesis of equal survival and timing of spring migration for High Arctic breeding sanderling Calidris alba using six and eight winter destinations between 55°N and 25°S, respectively.
Annual apparent survival was considerably lower for adult birds wintering in tropical West Africa (Mauritania: 0.74 and Ghana: 0.75) than in three European sites (0.84, 0.84 and 0.87) and in subtropical Namibia (0.85). Moreover, compared with adults, second calendar‐year sanderlings in the tropics, but not in Europe, often refrained from migrating north during the first possible breeding season. During northward migration, tropical‐wintering sanderlings occurred at their final staging site in Iceland 5–15 days later than birds wintering further north or south. Namibia‐wintering sanderlings tracked with solar geolocators only staged in West Africa during southward migration.
The low annual survival, the later age of first northward migration and the later passage through Iceland during northward migration of tropical‐wintering sanderlings, in addition to the skipping of this area during northward but not southward migration by Namibia‐wintering sanderlings, all suggest they face issues during the late non‐breeding season in West Africa.
Migrating sanderlings defy long distances but may end up in winter areas with poor fitness prospects. We suggest that ecological conditions in tropical West Africa make the fuelling prior to northward departure problematic.
besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2656.13118