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Numenius americanuslong-billed curlew

By William Bellamy

Geographic Range

Long-billed curlew (Numenius americanus) breeding areas range throughout the western United States and as far north as southern Canada. Their breeding range extends from eastern New Mexico northwards to the western Dakotas and into south Saskatchewan. Following grasslands and valleys in the Rocky Mountains, long-billed curlews range southwards from Alberta, through Montana and Wyoming into the Nevada Great Basin, and northwards through Oregon and Washington to the Fraser Plateau in British Columbia. Outside the breeding season, long-billed curlews range along the western coastline of North America starting as far north as Cape Flattery and extending as far south as El Salvador. They are also found across northern Mexico as far south as Mexico City, and along the eastern Mexican coast from the Yucatan peninsula to Vermillion Bay Louisiana. Other isolated ranges include midwestern Texas, and small Costa Rican populations recorded in the Gulf of Nicoya, and the Golfo Dulce coastline between Puerto Jiménez and Pavones. ("Species assessment for long-billed curlew (Numenius americanus) in Wyoming", 2004; "Numenius americanus", 2012; Colwell and Mathis, 2001; Gregory, et al., 2012; Jones, et al., 2008; Page, et al., 2014)

Habitat

The habitat of breeding long-billed curlews consists primarily of grasslands, with the majority of individuals inhabiting shortgrass prairie, followed by pasture grasslands and cultivated cropland. Curlews show no significant occupational tendencies between dry and irrigated land, but tend to occupy wide-open areas with vegetation 4 to 15 cm tall. In winter they live primarily in intertidal areas and mudflats, as well as foraging in nearby pastures. ("Species assessment for long-billed curlew (Numenius americanus) in Wyoming", 2004; "Numenius americanus", 2012; Leeman, et al., 2001; Pampush and Anthony, 1993; Saalfield, et al., 2010)

Physical Description

Long-billed curlews are long-legged shorebirds characterized by their long, decurved bills. The plumage in adult curlews is brown to buff, and contains noticeable hints of darker browns and pinks. Dark brown streaks and bars are present on their upper body, with orange brown upper remiges and cinnamon-colored underwing coverts and axillaries. Unlike many other curlew species, long-billed curlews have streaked rather than striped crowns. In their species assessment, Dark-Smiley and Keinath (2004) note only a small difference in size between sexes, with females slightly larger than males, but no numerical data were reported. ("Species assessment for long-billed curlew (Numenius americanus) in Wyoming", 2004; Redmond and Jenni, 1982)

Long-billed curlews weigh 490 to 950 grams and are 50 to 65 cm long. Their wingspan is 62 to 101 cm long. ("Species assessment for long-billed curlew (Numenius americanus) in Wyoming", 2004; Redmond and Jenni, 1986)

Juvenile long-billed curlews can be identified by their wing coverts, which have dark brown centers. They also lack the dark brown barring and pale notches characterized by adults. Juveniles can also be identified by their brighter coloration and shorter beaks. ("Species assessment for long-billed curlew (Numenius americanus) in Wyoming", 2004; Redmond and Jenni, 1986)

  • Sexual Dimorphism
  • female larger
  • Range mass
    490 to 950 g
    17.27 to 33.48 oz
  • Average mass
    790 g
    27.84 oz
  • Range length
    50 to 65 cm
    19.69 to 25.59 in
  • Average length
    61 cm
    24.02 in
  • Range wingspan
    62 to 101 cm
    24.41 to 39.76 in
  • Average wingspan
    77 cm
    30.31 in

Reproduction

Male long-billed curlews solicit mates by a combination of ground calls and vocal-bounding flights consisting of perimeter or figure-8 patterned flights. These displays are used to attract females to the males' territory. When females are present they then will orient these flights around them. As females fly through a nesting area, these displays intensify as all unpaired males rise and perform bounding flights. If a female is unpaired, she will land in the nest field of one of the males, often wandering through many territories over the course of several days until a mate is chosen. She and her mate will then familiarize themselves with one another, mate, and form a monogamous pair bond. If an unpaired female lands in an unpaired males nesting area, but does not choose to remain and form a pair, then the male will spend less time soliciting females and spend more time on the ground foraging. ("Species assessment for long-billed curlew (Numenius americanus) in Wyoming", 2004; Allen, 1980)

Long-billed curlews breed once per year from late March to late July. Breeding females lay their eggs in one clutch in June averaging 4 eggs per clutch. Their eggs are a light beige or a pale blue-green color with chocolate colored splotches. Redmond (1986) reports that long-billed curlew eggs are, on average, 65.3 mm long and 46.1 mm wide. Breeding pairs take turns incubating the eggs, with the female sitting during the day, and the male in the evening. ("Species assessment for long-billed curlew (Numenius americanus) in Wyoming", 2004; Allen, 1980; Hartman and Oring, 2009; Redmond and Jenni, 1986; Redmond, 1986)

Long-billed curlew chicks hatch after an incubation period averaging 27 days. Chicks start their pip hole (the hole which the chick enlarges during hatching to exit the eggshell) 21 mm from the larger end of the egg, and all chicks in a clutch will typically finish hatching within 5 hours of one another. Newly hatched chicks have a birth mass between 44 and 66g. Chicks begin to fledge between 32 and 45 days of hatching, and become independent 35 to 49 days after hatching, shortly after learning to fly. They reach reproductive maturity after 2 years. (Allen, 1980; Redmond and Jenni, 1986)

  • Breeding interval
    Long-billed curlews breed once yearly
  • Breeding season
    Late March to late July
  • Average eggs per season
    4
  • Average time to hatching
    27 days
  • Range fledging age
    32 to 45 days
  • Range time to independence
    35 to 49 days
  • Average age at sexual or reproductive maturity (female)
    2 years
  • Average age at sexual or reproductive maturity (male)
    2 years

Long-billed curlews nest on the ground; both males and females form a nesting bowl by scraping and poking the ground into a small depression. The nests are lined with locally available insulating materials like leaves, grass, stems, and twigs. Notably, nests are only insulated depending on local availability around the nesting site, and nests in areas with more sparse vegetation have substantially less insulation than those in other areas. In the presence of a mammalian predator, long-billed curlews will display at the predator, and attempt to draw them away by feeding nearby while calling rapidly, but no effort will be made to drive them from the nest. They will, however, guard their eggs against avian predators, driving them away from the nest. Incubation of eggs occurs in shifts; typically females will sit on the eggs during the day, and males will take over in the early evening. Shortly after hatching, long-billed curlews defend against avian predators much more aggressively, and the remains of the eggshells are removed from the nest and deposited several hundred meters away from the nest. Their territoriality also narrows in scope, and at this point they evict other long-billed curlews in a radius around their chicks rather than from the entirety of their territory.

Long-billed curlews do not feed their young, and chicks hunt in a similar manner as their parents. Both sexes watch over their young initially, and chicks are watched closely despite their tendency to wander far from the rest of their brood. Chicks can range as far as 100 meters away from a parent over the course of the day, before being ushered back to the nest area by the observing parent to roost at night. After 2-3 weeks, female curlews will typically abandon the brood, leaving only the male to care for the chicks. The juveniles fledge several weeks later, and after they have learned to fly, they are considered independent. (Allen, 1980)

Lifespan/Longevity

Redmond and Jenni (1986) suggest that long-billed curlews may live on average from 8-10 years, reporting a 15% mortality rate per year after they reach 2 years old. However, it is more likely that their lifespan is much longer than that, as other species in the genus Numenius can live between 23 and 32 years. (AnAge, 2016; Redmond and Jenni, 1986)

Behavior

Long-billed curlews are primarily diurnal, spending the majority of their time foraging. They move between foraging sites by a combination of flight and short glides. Non-breeding individuals are primarily solitary animals, although they often form mixed-sex flocks during migratory flights and at winter roosts. Long-billed curlews typically remain on their claimed territories, which they guard against other intruding individuals and predators. They have been observed leaving their territories during the hottest parts of the day, often foraging in cooler areas. During these periods of absence, individuals from neighboring areas will commonly trespass and forage on the absent curlew's territory. ("Species assessment for long-billed curlew (Numenius americanus) in Wyoming", 2004; Allen, 1980; Colwell, et al., 2002)

Male long-billed curlews perform aggressive displays and antagonistic actions towards one another at boundaries between individual territories. Despite this territorial activity they also cooperate in mobbing activities to protect eggs and chicks when a predator is present. (Allen, 1980; Redmond and Jenni, 1982)

Home Range

Colwell et al. (2002) reported home ranges of 1.3 - 7.5 ha. across a 9-month study. Long-billed curlews, on average, maintain home ranges of 3.0 ha during the summer, and 2.3 ha during the winter. These ranges can deviate up to 70% depending on the density of local prey populations, and individuals consuming a higher proportion of crabs have been noted to maintain larger home ranges, possibly due to higher distance between prey aggregations. (Colwell, et al., 2002)

Communication and Perception

Long-billed curlews perceive their prey primarily by sight, and communication between individuals typically consists of calls and displays. They produce a distinctive call year-round consisting of a two-note whistle. This low-high whistle is observed in both sexes and is both an anxiety tone and a contact call between members of the flock. Their calls can vary seasonally, with some alarm calls observed only during the breeding season between incubation and fledgling stages. Long-billed curlews use territorial displays to remove intruders; these include flying directly at an intruder before pulling up steeply, and crouch runs followed by an aerial chase. Communication during breeding season also include acoustic displays like ground-calls, and visual flight displays in males. (Forscythe, 1970)

Food Habits

Long-billed curlews diet consists primarily of small invertebrates and wild fruits, with those individuals inhabiting inland areas and grasslands mainly consuming a variety of earthworms, spiders, grasshoppers, beetles, and caterpillars. In coastal areas, they prey upon various bivalves, marine worms, mollusks, crustaceans, and some fish. Some consumption of other bird’s eggs and nestlings has been observed as well. They forage either singly, or in groups of up to 15 individuals by pecking food from the ground or water with their long bills. They also probe loose ground, mud, and sand in search of prey, and have exhibited some insect hawking behaviors. Curlews forage almost exclusively during the day, and have little diet change seasonally within their respective breeding and non-breeding ranges. ("Species assessment for long-billed curlew (Numenius americanus) in Wyoming", 2004; Leeman, et al., 2001)

  • Animal Foods
  • fish
  • eggs
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • terrestrial worms
  • aquatic or marine worms
  • aquatic crustaceans
  • Plant Foods
  • fruit

Predation

Adult long-billed curlew are preyed upon primarily by raptors like Swainson's hawk (Buteo swainsoni) and the ferruginous hawk (Buteo regalis). Land predators like coyotes (Canis latrans), feral dogs (Canis lupus familiaris), and red foxes (Vulpes vulpes) prey upon hatchlings and injured or nesting adults. In the past, humans (Homo sapiens) were the primary predator of adult long-billed curlews, and drove them nearly to extinction until hunting them was outlawed. Long-billed curlew eggs are more common targets for predation, and after a nest is raided the parents abandon the clutch. Redmond and Jenni (1986) found that the majority of eggs lost are consumed by coyotes and feral dogs, followed by badgers (Taxidea taxis), and birds such as the common raven (Corvus corax) and black-billed magpie (Pica hudsonia). ("Species assessment for long-billed curlew (Numenius americanus) in Wyoming", 2004; Allen, 1980; Redmond and Jenni, 1986)

Ecosystem Roles

Long-billed curlews compete for resources with other shorebirds on their winter ranges, notably godwits Limosa fedoa and willets Catoptrophorus semipalmatus. They prey primarily on invertebrates (both terrestrial and marine) and are preyed upon by hawks and canids. ("Long-billed Curlew (Numenius americanus): a technical conservation assessment", 2006)

Long billed curlews can be host to several species of lice, including Austromenopon crocatum, Cummingsiella longistricola, and Lunaceps numenii numenii. They may also be host to parasitic intestinal flatworms, including Brachylaema fuscata, Dictymetra numenii, Dictymetra nymphae, Dictymetra paranumenii, and Dictymetra radiaspinosa. Spiny-headed parasitic worms such as Mediorhynchus papillosus and Mediorhynchus robustus can inhabit their intestines. Parasitic flatworms (Selfcoelum lamothei) can be found in the air sacs of long-billed curlews. ("Species assessment for long-billed curlew (Numenius americanus) in Wyoming", 2004; Blend and Dronen, 2007; Butler and Pfaffenberger, 1981; Goater and Bush, 1988)

Commensal/Parasitic Species
  • Lice Austromenopon crocatum
  • Flatworm Brachylaema fuscata
  • Lice Cummingsiella longistricola
  • Flatworm Dictymetra numenii
  • Flatworm Dictymetra nymphae
  • Flatworm Dictymetra paranumenii
  • Flatworm Dictymetra radiaspinosa
  • Spiny-headed worm Mediorhynchus papillosus
  • Spiny-headed worm Mediorhynchus robustus
  • Lice Lunaceps numenii numenii
  • Flatworm Selfcoelum lamothei

Economic Importance for Humans: Positive

Bird watching and ecotourism positively contribute to the economy both in travel costs and bird watching equipment. Ecotourists observing shorebirds in their natural environment would likely attempt to observe long-billed curlews, as they are one of the largest sandpipers native to North America, and have very distinctive long, curved bills. (Edwards, et al., 2011)

Economic Importance for Humans: Negative

There are no known adverse effects of long-billed curlews on humans.

Conservation Status

Long-billed curlews have no special status on the US Federal List or CITES. The IUCN Red List considers them to be a species of "Least Concern" despite a slightly negative population trend. They are protected under the US Migratory Bird Act. Despite their protected status, adult mortality rates indicate illegal hunting continues to be a problem. The U.S. Shorebird Conservation Plan categorizes them as "highly imperiled" due to their threatened habitat and persisting declines in population.

Though they were severely over hunted in the past, the greatest threat to their population is now the habitat loss from both urban growth and wetland drainage. There is little known about the effects of pesticides on long-billed curlews, but insecticides may affect them indirectly by reducing the abundance of arthropods.

The American Bird Conservancy has increased awareness of long-billed curlews threatened habitat as a representative example of how losses of short grass prairie have affected local species. Several protected grassland areas contain long-billed curlews, and global population estimates have been proposed to identify threats to the species. ("Species assessment for long-billed curlew (Numenius americanus) in Wyoming", 2004; "Numenius americanus", 2012)

Contributors

William Bellamy (author), Radford University, Cari Mcgregor (editor), Radford University, Zeb Pike (editor), Radford University, Karen Powers (editor), Radford University, April Tingle (editor), Radford University, Jacob Vaught (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

diurnal
  1. active during the day, 2. lasting for one day.
ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

female parental care

parental care is carried out by females

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

young precocial

young are relatively well-developed when born

References

USDA Forest Service. Long-billed Curlew (Numenius americanus): a technical conservation assessment. None. Durango, Colorado: Ecosphere Ecological Services. 2006. Accessed March 24, 2016 at http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5182037.pdf.

BirdLife International. 2012. "Numenius americanus" (On-line). The IUCN Red List of Threatened Species Version 2012.5. Accessed January 28, 2016 at http://www.iucnredlist.org/details/22693195/0.

United States Department of the Interior. Species assessment for long-billed curlew (Numenius americanus) in Wyoming. None. Laramie, Wyoming: Wyoming Natural Diversity Database. 2004. Accessed February 14, 2016 at http://www.uwyo.edu/wyndd/_files/docs/reports/speciesassessments/long-billedcurlew-jan2004.pdf.

Allen, J. 1980. The ecology and behavior of the long-billed curlew in southeastern Washington. Wildlife Monographs, 73: 3-67.

AnAge, 2016. "AnAge Data Survey - Numenius" (On-line). Accessed March 25, 2016 at http://genomics.senescence.info/species/survey.php?ids%5B%5D=01287&ids%5B%5D=01288&ids%5B%5D=01289&cmd=var.

Blend, C., N. Dronen. 2007. Selfcoelum lamothei n. sp. (Digenea: Cyclocoelidae: Cyclocoelinae) from the air sacs of the long-billed curlew, Numenius americanus (Scolopacidae), from the Galveston, Texas area, USA. Revista Mexicana de Biodiversidad, 79: 41-48.

Butler, W., G. Pfaffenberger. 1981. Notes on parasites of the long-billed curlew, Numenius americanus, from eastern New Mexico. Journal of Wildlife Diseases, 17/4: 537-538.

Colwell, M., R. Mathis. 2001. Seasonal variation in territory occupancy of non-breeding long-billed curlews in intertidal habitats. Waterbirds, 24/2: 208-216.

Colwell, M., R. Mathis, L. Leeman, T. Leeman. 2002. Space use and diet of territorial long-billed curlews (Numenius americanus) during the non-breeding season. Northwestern Naturalist, 83/2: 47-56.

Edwards, P., G. Parsons, K. Myers. 2011. The economic value of viewing migratory shorebirds on the Delaware Bay: an application of the single site travel cost model using on-site data. Human Dimensions of Wildlife, 16/6: 435-444.

Forscythe, D. 1970. Vocalizations of the long-billed curlew. The Condor, 72/2: 213-224.

Goater, C., A. Bush. 1988. Intestinal helminth communities in long-billed curlews: The importance of congeneric host-specialists. Holarctic Ecology, 11/2: 140-145.

Gregory, C., S. Dinsmore, L. Powell, J. Jorgenson. 2012. Estimating the abundance of long-billed curlews in Nebraska. Journal of Field Ornithology, 83/2: 122-129.

Hartman, A., L. Oring. 2009. Reproductive success of long-billed curlews (Numenius americanus) in northeastern Nevada hay fields. The Auk, 126/2: 420-430.

Jones, S., C. Nations, S. Fellows, L. McDonald. 2008. Breeding abundance and distribution of long-billed curlews (Numenius americanus) in North America. Waterbirds, 31/1: 1-14.

Leeman, L., M. Colwell, T. Leeman, R. Matthis. 2001. Diets, energy intake, and kleptoparasitism of nonbreeding long-billed curlews in a northern California estuary. Wilson Bulletin, 113/2: 194-201.

Page, G., N. Warnock, L. Tibbitts, D. Jorgenson, A. Hartman, L. Stenzel. 2014. Annual migratory patterns of long-billed curlews in the American West. The Condor, 116/1: 50/61.

Pampush, G., R. Anthony. 1993. Nest success, habit utilization and nest-site selection of long-billed curlews in the Columbia Basin, Oregon. The Condor, 95/4: 957-967.

Redmond, R. 1986. Egg size and laying date of long-billed curlews Numenius americanus: Implications for female reproductive tactics. Oikos, 46/3: 330-338.

Redmond, R., D. Jenni. 1982. Natal philopatry and breeding area fidelity of long-billed curlews (Numenius americanus): Patterns and evolutionary consequences. Behavioral Ecology & Sociobiology, 10/4: 277-279.

Redmond, R., D. Jenni. 1986. Population ecology of the long-billed curlew (Numenius americanus) in western Idaho. The Auk, 103/4: 755-767.

Saalfield, S., W. Conway, D. Haukos, M. Rice, S. Jones, S. Fellows. 2010. Multiscale habitat selection by long-billed curlews (Numenius americanus) breeding in the United States. Waterbirds, 33/2: 148-161.

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