SPECIES

Bristle-thighed Curlew Numenius tahitiensis Scientific name definitions

Jeffrey S. Marks, T. Lee Tibbitts, Robert E. Gill, and Brian J. McCaffery
Version: 1.0 — Published March 4, 2020
Text last updated January 1, 2002

Diet and Foraging

Feeding

Main Foods Taken

On breeding grounds, insects and spiders, as well as fruits and flowers of dwarf shrubs. Highly opportunistic on wintering grounds, taking intertidal and terrestrial invertebrates, seabird eggs and hatchlings, carrion, lizards, rodents, and fruits.

Microhabitat For Foraging

See Distribution and Habitat, above. On breeding grounds, forages primarily in dwarf-shrub meadow tundra on slopes and ridges. Meadows composed of variable amounts of ericaceous shrubs, black crowberry, cottongrass (Eriophorum), sedges (Carex spp.), lichens, and mosses (Sphagnum). Also forages on streamside berms and terraces. Less frequently forages in wetlands and medium-shrub (0.5-1.0 m tall) habitats including marshy streambeds, stream shorelines, shallow lakes, moss or grass/sedge understory along margins (rarely interiors) of willow thickets, and lingonberry and Labrador tea understory around dwarf birch thickets. On staging grounds, foraging birds most common in tundra/meadow mosaic (BJM, REG, TLT).

Uses all main terrestrial habitats in Northwestern Hawaiian Is., but feeds more commonly among inland vegetation than on beaches or intertidal zone (JSM). On Laysan and Lisianski Is., preferred foraging habitats include mats of beach morning glory and stands of native bunchgrass and introduced sandbur (Cenchrus echinatus); curlews on Midway Atoll forage more commonly on lawns and antenna fields composed of introduced grasses than on beaches or in native vegetation (JSM). Similarly, curlews on Caroline Atoll conspicuous on beaches and reef flats, but higher numbers may forage inland during the day, particularly in Ipomoea interspersed with Boerhavia and Phymatosorus and also beneath canopy of Cocos and Pisonia forest (Kepler et al. 1994). Feeds on open flats on Fanning I. (Kirby 1925) and in marshes and dry meadows on Nukuhiva I. (Holyoak 1975a). On high volcanic islands in French Polynesia, forages on beaches, meadows up to 800 m elevation, fern-covered slopes, and all wetland types except rivers (Holyoak and Thibault 1984); on Rangiroa Atoll, forages mostly in saltpans and channels among islets (Gill and Redmond 1992).

Food Capture And Consumption

Adults walk at steady pace with occasional quick chases after mobile prey such as crabs, spiders (Araneae), and lizards. Uses many different foraging techniques. On breeding grounds, runs across snowfields in pursuit of spiders; after snow melts, shallowly probes tundra for invertebrates, deftly picks individual fruits and flowers off low and prostrate shrubs, occasionally snatches insects off lake surfaces or out of air, shakes pupae out of cocoons, and searches for invertebrates by pulling up and vigorously thrashing small clumps of lichen and moss (clumps then tossed to ground and examined). Young chicks glean insects, berries, and flowers from ground and low shrubs and snag insects out of air. Fall staging birds pick berries and glean insects from dwarf shrubs and shallowly probe wet meadows, mudflats, slough banks, and bases of water plants for invertebrates.

Rate of berry consumption in Nulato Hills averaged 11.2 ± 1.67 SE (n = 27 adults across breeding season) per 6-min sample (BJM). Intake rates varied seasonally; curlews consumed 15 berries/6 min ± 2.01 SE (n = 20) before onset of blueberry flowering and 6.4 berries/6 min ± 2.37 SE (n = 16) during flowering period. When foraging on blueberry flowers, intake rates at Curlew Lake averaged 48 blossoms/6 min ± 11.7 SE (n = 13), or 8 blossoms/min; peak rate for individual 45.3/min (BJM).

In winter, probes for invertebrates in low-growing vegetation, sandy beaches, seaweed mats, mudflats, and exposed coral reefs (Child 1956, Holyoak and Thibault 1984, JSM). Uses “slamming” (see Figure 3) to dismember crabs and snails (Marshall 1951, Child 1956, Carpenter et al. 1968, Marks and Hall 1992), and to kill and dismember house mice (Mus musculus) and Polynesian rats (Rattus exulans) so they can be swallowed (Woodward 1972b, Amerson and Shelton 1976, Kepler et al. 1994, JSM). Slamming birds hold food in bill, raise it overhead, and vigorously throw it against flat rock or ground (Marks and Hall 1992). Procedure repeated until item broken into pieces (crabs) or opened (snails, bird eggs). Birds carry food up to 30 m to suitable slamming substrate (JSM). Slamming likely innate because fledglings (but not adults) in Alaska slam nonfood items (REG, TLT). Opportunistically takes abandoned or unattended seabird eggs (JSM), less often plucks eggs from beneath incubating terns (Sterna spp.) and Great Frigatebirds (Fregata minor; Wetmore 1925a, Bailey 1956a). Opens eggs by slamming, dropping on hard surface, poking hole in shell (Bailey 1956a, Ely and Clapp 1973, JSM), and enlarging holes made in large and thick-shelled eggs (e.g., albatross [Phoebastria spp.]) by Ruddy Turnstones (Arenaria interpres; Marks and Hall 1992). In a variation of slamming behavior, employs tools to get at egg contents by tossing small pieces of coral at eggs to break them (Figure 3); such tool use unique among shorebirds (Marks and Hall 1992).

Opportunistic foraging behavior illustrated by observations from Laysan I. (JSM). Flying adult wheeled to ground and “pounced” (using bill) on snake-eyed skink (Cryptoblepharus boutonii). Curlews also grab strings of flying fish (Exocoetidae) eggs from mouths of albatross chicks, sometimes jumping off ground in process, and pursue and capture live bait fish driven to beach by predatory fish. Munro (Munro 1942a: 2–3) noted that in 1891, the caretaker on Laysan I. “used to hang a cloth outside his door overnight. In the morning he shook out the moths . . . and a flock of curlews that were on the watch would run up and catch them as they fluttered off.” One hundred years later, curlew ate moths (Lepidoptera) knocked from tent flaps in camp on Laysan I. (JSM).

Diet

Major Food Items

Upon arrival on breeding grounds, consumes previous summer's black crowberries, lingonberries, and bog cranberries (Vaccinium oxycoccus), less frequently bog blueberries and alpine bearberries; also spiders, beetles (Coleoptera; adults and larvae), moths, and butterflies (Lepidoptera; larvae and pupae). Previous year's berry crop dwindles as season progresses, becoming almost nonexistent by mid-Jun in dry years; curlews then switch to blueberry flowers (available in good quantities for 2–3 wk in Jun) and winged and larval insects (plentiful by early Jun). During early brood-rearing (late Jun–early Jul), insects probably most important food for parents and young chicks. By mid-Jul, adults and older chicks move to areas with plentiful ripening bog blueberries (BJM, REG, TLT). Migrants on Yukon Delta eat bog blueberries, black crowberries, cloudberries (Nelson 1887a, Bent 1929), and a variety of aquatic and terrestrial insects (TLT, REG). Occasionally takes vertebrates; e.g., curlew tried to swallow Black-bellied Plover (Pluvialis squatarola) chick regurgitated by gull (Larus sp.; C. Babcock pers. comm.).

Feeds mostly on invertebrates in Northwestern Hawaiian Is., including ghost crabs (Ocypode laevis), isopods (Porcellionides sp.), spiders, roaches (Blattidae), earwigs (Labiduridae), cutworm moths (Noctuidae), and sphinx moths (Sphingidae); also eats carrion (e.g., dead seabirds), fish and squid regurgitated by seabirds, seabird hatchlings (e.g., Bonin Petrel [Pterodroma hypoleuca], Tristram's Storm-Petrel [Oceanodroma tristrami]), seabird eggs, adults and possibly eggs and nestlings of Laysan Finches (Telespiza cantans), introduced lizards, house mice, and fruits of Scaevola taccada (Bartsch 1922, Ely and Clapp 1973, Morin and Conant 2002, JSM). South of Hawaiian Is., eats snails (Nerita spp.; Carpenter et al. 1968, Gill and Redmond 1992), fiddler crabs (Uca sp.; Bakus 1967, R. Redmond pers. comm.), hermit crabs (Coenobita sp.; Gill and Redmond 1992), Polynesian rats (Kepler et al. 1994), and variety of unclassified intertidal and terrestrial invertebrates (e.g., Holyoak 1980, Holyoak and Thibault 1984).

Predation on seabird eggs perhaps not as prevalent as in past. Accounts of this behavior on Laysan I. (e.g., Wetmore 1925a, Bailey 1956a) from period when vegetation nearly eliminated by European rabbits (Oryctolagus cuniculus), which must have reduced insect availability considerably. In 1990s, curlews seldom fed on seabird eggs at Laysan I. but were more likely to do so on Tern I., which contains little vegetated habitat preferred by foraging curlews (JSM).

Quantitative Analysis

Three stomachs from adults on Seward Peninsula breeding grounds late Jun to mid-Jul contained berries (1 with blueberries, 2 with black crowberries), 2 with land snails (Gastropoda), 2 with adult ground beetles (Carabidae), 1 with snout beetles (Curculionidae [adult]) and water beetles (Haliplidae [larvae]), and 1 with bees (Apidae). Stomach of 2-wk-old chick from same location had only black crowberries. From Yukon Delta staging grounds mid-Jul, stomachs of 2 birds collected while feeding together both had adult crane flies (Tipulidae) and well-digested remains of downy birds (Scolopacidae, Motacillidae, or Emberizidae); 1 also contained marine snails (Littorina sitkana), adult bees, adult ground beetles, and spiders (REG).

Stomachs from 14 birds collected in the Tuamotu Archipelago (expressed as percentage of occurrence among stomachs) contained vegetation (50.0%), crustaceans (35.7%), insects (28.6%), gastropods (7.1), and scorpions (7.1); latter had remains of ≥15 scorpions (Hormurus australasiae; Mougin and Stockmann 1969, Lacan and Mougin 1974a). Emetic given to 27 birds caught at night on Laysan I.; of 13 birds that regurgitated food, 7 produced earwigs, 2 ghost crab parts, 1 a spider, and 3 a mix of unidentified invertebrates (JSM).

Food Selection and Storage

Highly opportunistic on wintering grounds, although when presented with ghost crabs in controlled feeding trials, some individuals “specialists” that killed and processed crabs quickly, whereas others appeared to fear crabs and would not pursue them (JSM). Not known to store food.

Nutrition and Energetics

No information.

Metabolism and Temperature Regulation

On hot days, birds roosting at rock ledges on Laysan I. routinely pant with open mouth and hold wings away from body (JSM); also seek shade under vegetation and next to rock ledges in Northwestern Hawaiian Is. and Tuamotu Archipelago (JSM, REG).

Drinking, Pellet-Casting, and Defecation

Drinks from freshwater seeps on Laysan I. but also readily drinks seawater at tide pools and shoreline (JSM). Routinely casts pellets on wintering grounds; fresh pellet on Laysan I. measured 14.3 × 29.5 mm and was similar in size to many others not measured (JSM). Pellet-casting never documented from breeding or staging grounds. Regularly defecates when foraging and roosting and especially when captured by researchers.

Bristle-thighed Curlew Bog cranberries, key food for Bristle-thighed Curlews in late spring
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Bog cranberries, key food for Bristle-thighed Curlews in late spring

Bog Cranberries, Vaccinium oxycoccus, a key food for Bristle-thighed Curlews arriving on Alaskan breeding grounds in late spring. These berries represent a crop from the previous season. Central Seward Peninsula, Alaska.  June. © Lee Tibbitts; photographer Lee Tibbitts

Bristle-thighed Curlew Figure 3. Feeding behavior of Bristle-thighed Curlew
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Figure 3. Feeding behavior of Bristle-thighed Curlew

Bristle-thighed Curlew using stone tool to open albatross egg (after Marks and Hall 1992). Motion in upper panel same as slamming behavior in which food item (versus stone) grasped in bill-tip and thrown at hard surface. Illustration by R. Petty.

Recommended Citation

Marks, J. S., T. L. Tibbitts, R. E. Gill, and B. J. McCaffery (2020). Bristle-thighed Curlew (Numenius tahitiensis), version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.brtcur.01