The curlew sandpiper (Calidris ferruginea) is a small wader first described in 1763 by Erik Pontoppidan in the tringa family before being moved to its current genus, calidris, in 1804 by Blasius Merrem. They have numerous plumages, with the two main ones being non-breeding and breeding. The non-breeding plumage has brown-greyish upperparts, with the areas near the head and the breast being brighter. Their breeding plumage is largely distinct, with the entire frontside of the bird tinted a deep red. They are strongly migratory, wintering mainly in Africa, but also a long the coasts of Australasia and southeast Asia. They are a vagrant to North America. They breed in the Siberian arctics, remaining there from June to August. Its courtship behavior is complex, with multiple different displays on the ground or in the air. They lay only one clutch of eggs, usually around the end of June. They are omnivorous.
The curlew sandpiper was formally described in 1763 by the Danish author Erik Pontoppidan under the binomial nameTringa ferrugineus.[2] It is now placed with 23 other sandpipers in the genus Calidris that was introduced in 1804 by the German naturalist Blasius Merrem.[3][4] The genus name is from Ancient Greekkalidris or skalidris, a term used by Aristotle for some grey-coloured waterside birds. The specific ferruginea is from Latinferrugo, ferruginis, "iron rust" referring to its colour in breeding plumage.[5] The curlew sandpiper is treated as monotypic; no subspecies are recognized.[4] Within the genus Calidris the curlew sandpiper is most closely related to the stilt sandpiper (Calidris himantopus).[6][7]
Egg With red-necked stint, Manly Marina, SE Queensland, Australia
The curlew sandpiper is a small wader 21cm (8.3in) in length and weighing 57g (2.0oz),[10] with a wingspan of 38–46cm (15–18in),[11] a bill length of 32–44mm (1.3–1.7in), and a tarsus length of 26–34mm (1.0–1.3in).[12] Its bill is black, irises dark brown, and dark grey to black toes and tarsi.[13]
The curlew sandpiper's plumage varies seasonally; in non-breeding adults, upperparts are initially greyish and underparts white(occasionally with large grey streaks), however as feather wear increases they will both slowly become more brownish. The centers of their upperpart feathers are darker, especially on their crests, causing their upperparts to look motted. The uppertail coverts as well as the lower rump feathers are white, with broad, pale grey retrices. Their primaries and secondaries are dusky with white streaks along the shaft and a white tip. They have a distinctively white supercilium with greyish brown lores and auriculars.[13]
Breeding plumage is sexually dimorphic in returning breeders. In females the front side, the entire head, and their upper back are tinted variably reddish, with grey-to-dark streaks. The lower scapulars, along with the upperwing coverts and commonly the tertials are tipped ruddy-silver with black centers, resulting in a spotty appearance. The uppertail and upperwing coverts, along with the rump and flight feathers are all near identical to their non-breeding appearance, except for the central rectricies and/or 2-3 tertials, which are off-black with white or ruddy fringing. Male plumage is similar to that of females, except with the reddish tinting being almost completely opaque, and conspicuous spots above the eye and around the crown.[13]
Juveniles look similar to the adult non-breeding plumage, except for more evenly spread out wear marks and fringing, resulting in a scaly appearance, as well as a overall more buff-tinged appearance. The crown and nape are dusky with pale creamy streaks, with the nape being slightly more pale, and the rectrices are narrower and more tapered.[13]
First-time breeders also have a unique plumage similar to that of returning breeders, with the primary differences being white spots or tufts on the underparts, which is fully rufous instead of just a tint. Sex differences are also similar to returning breeders. This plumage is occasionally not present in some juveniles if not all molts were completed.[13]
Vocalizations
Only males sing. Each song lasts for 10-15 seconds and consist of several parts, starting with several introductory notes, followed by multiple trilled doublets, a four-part phrase, and several drawn out whine calls. Calls are uttered by both genders, and include the following:[14]
An alarm call, a whik, whik, whik repeated or wik-ki-ki-ki... used on breeding grounds to warn of potential threats.[14]
A chase call, a shrill, musical twittering similar to that of the Vaux's swift given primarily by the male but occasionally the female during courtship flights.[14]
A flight call, a chirrup that drops in the middle, usually uttered during takeoff.[14]
A whine call, an lound and ascending whaay, whaay, whaay similar to that of a plover (and nearly identical to the stilt sandpiper's whine) and audible hundreds of yards away. It is only given by males and seemed to be used for defending their territory.[14]
During non-breeding season, they are commonly found along sheltered mudflats, as well as saltpans and wetland edges; inland they occupy the edges of various bodies of water, especially if they have muddy or sandy coasts, they are additionally found along sewage ponds. They occupy coastal and inland wetlands during migration, and during breeding they mostly remain in lowland tundra near bogs, depressions, or pools, away from scrub and other dense vegetation.[13]
The curlew sandpiper is a common migratory vagrant in North America, especially along the Atlantic coast, with 17 per year observed along the Atlantic Seaboard between 1985 and 1994, compared to 2 per year on the Pacific coast from 2010 to 2020, and 1-2 per year inland (also 1985-1994).[13]
Migration
Curlew sandpipers show little fidelity to breeding sites, making it hard to predict where a specimen overwinters based on its breeding site, however, the reverse is not as true; adults tend to prefer overwintering in the same regions and rest at stopovers at the same points, and males were observed to be more faithful to their sites compared to females. Both sexes had their breeding plumage by the time they arrived at their breeding sites.[16]
Males depart from the breeding grounds when the female starts incubating, and females depart either when breeding fails or when the young successfully fledge. Fledglings migrate south soon after fledging, however they do not migrate for breeding their first breeding season, instead remaining in their overwintering range.[13][16]
Behaviour
The curlew sandpiper appears to be largely monogamous, however breeding habits are not well studied. Their behavior is similar to that of other shorebirds, walking, running and wading to move around.[13] Their flight speed during migration has been estimated to be around 70–75km/h (43–47mph).[17] They rarely swim while feeding.[18] They practice preening and bathing and have been observed scratching their heads with their claws and dipping their head in the water to clean it. They mainly roost in large mixed-species flocks on sandspits and lagoon islets; occasionally dunes, reefs, or beach wrack at high tide.[13]
Breeding
The curlew sandpipers forms pairs during northward migration.[19] Pairs usually arrive to their breeding site early June, and perform courtship mid-June. Females would move around an area about several acres large feeding, and the mail would follow her attently, trailing her 10–20ft (3.0–6.1m) away, occasionally vocalizing partial or complete songs, and conducted various courtship behaviors. Courtship behaviors included the following:[14]
Aerial courtship, where the male would pursue the female in long chases, occasionally catching up. When he did catch up, he lifted his wings horizontally, and glides torward the female while making trilling calls and occasionally performing his chase call. (the female also, although more rarely, performs the chase call.) The aerial chase closely resemble territorial conflicts, however unlike an aerial chase, which was lithe and graceful in comparison, the latter was much more erratic, with substantially more sharp turns and gyrations. After the pair landed, the male would then begin one of the ground courtship displays.[14]
Ground courthship attitude, where, during the prenesting period, the male would intermittently assume a "courtship" stance (lowered head, ruffled scapulars and back feathers, and bent legs, resulting in a hunched appearance) during feeding. It is often followed by a full ground courtship display, and seems to represent increased libido in males.[14]
A nest-cup display, one of two ground courtship displays and often preceeded by the courtship attitude behavior. The male would, in short bursts, move across the tundra, eventually stepping into a small depression. Once in the depression, he would settle down as if it were a nest, folding his wings over his back and rasing his tail, and proceed to wag his wings and tail side to side, occasionally crouching and kicking up lichen and moss with their claws. He would then stand up, picking various bits of vegetation from around him and deposit them by his feet in the faux nest. Even if the bit of vegetation were to slip, he still mime the motion of tossing it into the nest. This sequence would often be followed by him stamping his claws, or repeating the pressing motion from earlier, and during the sequence, he would occasionally make whine notes and trill calls. This display was not an act of nest-building, as it would be performed several times, each in different locations. Females would usually be a few yards away, but did not seem to be paying full attention to the display.[14]
A precopulary display, the other courtship display. Described as elaborate, this display would precede copulation, and would begin with both members would stand near each other. The male would raise his wing closer to the female, reaching an angle of about 60–70° with the horizontal, and raised the other wing to match it. He would also raise his head and fan and lower his tail. Following this, he would give a short series of trilling calls and sway back and forth, such that he would alternate being behind her and in front of her, attempting to display his fanned tail and rump to the female by having his back always face her. The female, who up to this point ignored his shenanigans, would dash and thrust her head torward the male's rump, occasionally overshooting such that her head was along the male's flank instead. After around a minute of this display, the female would turn away and the male, with his wings still held up high, would approach to mount and copulate.[14]
Breeding grounds are occupied from June till late August.[14] Nesting site is usually located at the edge of a marsh or pool, or on dry patches of tundra, often near nests of other curlew sandpipers. Clutches consist of 3-4 eggs (average 3.76), usually are laid over the course of three days. The first brood usually laid from late June to July, with especially early breeders laying eggs only 5–6 after arriving, with the majority of pairs finishing around the end of June.[13] A second brood may occur for some birds nesting in the far south of their breeding range if the first was unsuccessful.[20] Eggs are slightly pear-shaped and olive colored with large dark olive or brown splotches, with more splotches on the broad end, making it look a rounghy continous shade of olive-brown. Eggs are incubated solely by the female for 20 days.[13]
At birth, nestlings are precocial covered with down, and will begin to wander from the nest after drying. On average, they weigh 8.2g (0.29oz), with a bill length of 10.8mm (0.43in), a tarsus length of 23.2mm (0.91in), and a wingspan of 17mm (0.67in). The rate of the growth is porportional to the tempature, with lower temperatures coinciding with slower growth and vice versa. Nestlings are fed by the female and become completely independent at 14-20 days of age. By the time they fledge, they weigh on average 49.6g (1.75oz), with a bill length of 27.8mm (1.09in), tarsi 30.8mm (1.21in), and a wingspan of 94.5mm (3.72in).[21]
The reproductive success of this species appears to be dependent on the population of lemmings (West Siberian lemmings (Lemmus sibiricus), East Siberian lemmings (Lemmus paulus) and the Arctic lemming (Dicrostonyx torquatus). In poor lemming years, predatory species such as the Arctic fox (Alopes lagopus) will take Arctic-breeding waders instead.[22][23]
Territorial behaviors
Territorial marking and disputes are uncommon in the curlew sandpiper, with instances of pairs displaying complete disregard to territories of other pairs, however those areas were sparse and newly settled, and thus did not have the need to be defended. In more densely populated areas, curlew sandpipers display territorial behavior similar to that of other territorial birds, chasing off other birds, including dunlins, baird's sandpipers, and pectoral sandpipers. Territories varied from 1.6–4.0 hectares (4.0–9.9 acres) in size for pairs. Territorial behaviors included:[14]
Localized area of activity, with unprovoked aerial displays and 'whine' notes to announce territory.[14]
Chasing of intruders up to the edge of its territory, in flight or on the ground, similar to the aerial courtship display except more erratic, jagged and rapid. The ground aggressive display has only been observed once, and consisted of the male lowering the head and neck parallel to the ground, pulled back torwards the body, and fanned his tail, before running torwards the invading bird.[14]
Stopping chase at the boundaries of their territory, suggesting awareness of their neighbor's territory. Upon concluding a chase, they would often perform a flight-song while returning.[14]
Feeding and diet
The curlew sandpiper, like other waders, forage in large flocks (up to thousands) on tidal flats, shallows, marshes, saltflats, and sewage lagoons, picking up food by sight. They are active throughout the entire day and night, however the frequency at which they forage at night decreases as the time for northward migration approaches. It mostly eats insects and other small invertebrates like crabs, molluscs or worms, supplemented with various seeds.[13]
Status
Counts of the curlew sandpiper in South Africa, specifically at Langebaan Lagoon where they are most numerous, indicate a 40% decline in numbers between 1975 and 2009. A similar trend has been noted in Australia and may be linked to effects of global warming at the breeding grounds.[24] It has an extremely large range but although the population is large it is very hard to determine and appears to be decreasing. BirdLife International has judged the species to be vulnerable.[1] The curlew sandpiper is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.[25]
↑Wells, David; Round, Philip D.; Treesucon, Uthai (1999). The birds of the Thai-Malay Peninsula: covering Burma and Thailand south of the eleventh parallel, Peninsular Malaysia and Singapore. San Diego: Academic Press. ISBN978-0-12-742961-8.
↑Piersma, T.; van Gils, J.; Wiersma, P. (1996). "Curlew sandpiper". In del Hoyo, J.; Elliott, A.; Sargatal, J. (eds.). Handbook of the Birds of the World. Vol.3: Hoatzin to Auks. Barcelona, Spain: Lynx Edicions. pp.524–525. ISBN978-84-87334-20-7.
↑Marchant, S.; Higgins, P. J.; Ambrose, S. J.; Davies, S. J. J. F.; Steele, W. K., eds. (1990). Handbook of Australian, New Zealand & Antarctic birds. Melbourne; New York: Oxford University Press. ISBN978-0-19-553068-1.
↑"Species". Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA). Retrieved 27 November 2021.
Sources
Cramp, Stanley, ed. (1983). "Calidris ferruginea Curlew Sandpiper". Handbook of the Birds of Europe the Middle East and North Africa. The Birds of the Western Palearctic. Vol.III: Waders to Gulls. Oxford: Oxford University Press. pp.339–345. ISBN978-0-19-857506-1.
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