Gallinago delicata

Geographic Range

Wilson’s snipes Gallingano delicata are wide-ranging shorebirds that are found year-round in the northwestern United States, including areas of California, Nevada, Utah, Colorado, Wyoming, Montana, Idaho, Oregon, and Washington. The year-round range also includes parts of Michigan, Indiana, Ohio, Pennsylvania, and Canada (Ontario and British Columbia).

The nonbreeding distribution of Wilson’s snipes range south, covering all of Central America and as far south as northern Columbia and Venezuela in South America. This also includes the islands in the Caribbean and the continental United States of America from coast to coast. In the United States, the northern bounds are Massachusetts, Indiana, Wyoming, and Washington. The nonbreeding range also covers the western coast of Canada, as far north as the southern tip of Alaska.

The breeding range of Wilson’s snipes covers from the east coast to the western edge of Montana across the North American continent, extending as far south as New York, Michigan, North Dakota in the United States, and British Columbia, Canada. It ranges northward along the west coast of British Columbia, limited to the east side of the Coast Mountains and following the mountain range northward and into western Alaska. The breeding range extends north as far as Yukon Territory, Northwest Territories, Manitoba, Ontario, Quebec, and Newfoundland in Canada. Eastern boundaries of the breeding range are Maine in the United States, and Nova Scotia and the Island of Newfoundland in Canada.

• Biogeographic Regions
• nearctic nearctic
  • native native
• neotropical neotropical
  • native native

Habitat

During the winter, Wilson’s snipes are located in wet, marshland environments. These can include wet pastures, bogs, surrounding marshes and ponds, swamps, and short-grass marshes. During the breeding season, these locations extend to include sedge bogs, fens, willow Salix and alder Alnus swamps, and the edges of rivers and brooks, within a mean water depth of 35 mm. Wilson’s snipes tend to avoid areas of thick vegetation. They are typically found with enough vegetation to provide protection from predators.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial
• freshwater freshwater

• Wetlands
• marsh marsh
• swamp swamp
• bog bog

• Other Habitat Features
• riparian riparian

Physical Description

When Wilson’s snipes first hatch, they are covered in tan to dark brown down with some black spotting. A molt begins soon after incubation and is completed before the birds’ first migration. Some of the feathers are tipped with white at this age and there is a white streak across the crown of their heads. There are black facial stripes, running from bill to eye and a “dark moustachial streak” (Mueller, 1999).

Juveniles look very similar to adults, with the only distinguishable difference being juveniles’ slightly darker plumage at four weeks old. By the time the juveniles are six weeks old, their plumage has fully developed and they have the same appearance as adults.

Adult Wilson’s snipes very closely resemble common snipes Gallinago gallinago . The only variation in appearance is the presence of 16 rectrices, as opposed to 14 found on common snipes, with the lateral pair much narrower in Wilson’s snipes. Adult Wilson’s snipes’ wingspan ranges between 121 to 130 mm for males and between 117.5 and 135 mm for females. The length of the tails ranges between 52 and 63 mm for males and 50 to 58.5 mm for females. Other than the length of the feathers, Wilson’s snipes are monomorphic with an average body mass of 100 g and an average body length of 28 cm. There are no extreme differences in mass across age ranges and seasons. All of the adults have pale, narrow, median stripes and broad, black, lateral stripes that are marbled with a lighter brown. There also are four lines of light spots running dorsal from anterior to posterior. Their ventral plumage is lighter, buff marbled with spots of darker brown. Their overall plumage coloration is very cryptic to aid in camouflage from predators. Their bills are a pale, reddish brown at the base, getting darker along the bill, until becoming dark brown at the tip. Their feet and legs are greenish yellow or a blue-gray color. Juveniles have gray legs more frequently than adults. Their claws range from dark brown to black.

• Other Physical Features
• homoiothermic

• Sexual Dimorphism
• sexes alike

Reproduction

Wilson’s snipes are polyandrous, as one female mates with multiple males. However, after mating is complete, the birds form pairs, with one male and one female.

Males arrive to the mating site 10-14 days before the females arrive. Pair formation does not occur until the females choose a nest site and start laying eggs. The females select a nesting site in wetlands. To start the nest-building, females dig a shallow hole with their beaks. Females then weave the nest with coarse grass and line the nest with fine grass. Males begin assisting the females after the nest has been built.

• Mating System
• polyandrous polyandrous

Wilson’s snipes have one breeding season per year, between mid-April and August. Clutches of 3-4 eggs are typical, with an occasional clutch having only two. The eggs typically are laid a day apart, with the females adding fine grass between laying each egg. If the females lose a clutch, they can lay a replacement clutch approximately 14 days later. Incubation lasts 18-20 days, with each egg hatching within a couple hours of each other. Hatching can last between half an hour and ten hours, with a median of 5-6 hours. The chicks can be heard chirping at least 24 hours before hatching. The females also exhibit signs when the chicks are close to hatching, such as clucking, ruffling their feathers, and spreading their tails. Chicks weigh about 10% of their adult weight at hatching, usually around 11g. Their down is dark red or black-brown with fine white spots, their legs a deep olive-grey, and they have short, squat, black beaks. The chicks reach fledgling stage by 18-20 days, where they leave the parents and become independent, though they can fly very short distances by 14 days. Common snipe Gallinago gallinago males and females reach sexual maturity at approximately 365 days. Wilson’s snipes and common snipes were once considered the same species and have similar ages of sexual maturity.

• Key Reproductive Features
• seasonal breeding seasonal breeding

Female Wilson’s snipes are the primary caretakers of the nest and eggs. Once male and female pair formations have occurred, the males have investment in the hatchlings, with little investment in the nests themselves. The females incubate all night; in the brief periods that they have to get off the nest to eat, the males take over temporarily. Both males and females invest in raising their young. The males leave the nest with the first two hatched chicks and the females leave with the remaining. Once this split has been made, the males and females have no further contact with each other. Parents feed the young for several weeks by pre-mastication, depositing the food directly into the young’s mouth.

• Parental Investment
• male parental care male parental care
• female parental care female parental care
• pre-hatching/birth
  • provisioning
    • male
    • female
• pre-weaning/fledging
  • provisioning
    • male
    • female
• pre-independence
  • provisioning
    • male
    • female

Lifespan/Longevity

The oldest known Wilson’s snipe in North America, based on band recovery, survived 12 years. It has been reported, also based on band recovery, that life expectancy at 3 months of age is 1.3 years, then after they reach a year old, their life expectancy increases to 1.5 years. Wilson's snipes are not known to be kept in captivity.

Behavior

Wilson’s snipes do not climb, but they will perch on trees and posts from flight. They will usually walk to feeding areas but can also run and will fly when traveling distances over 70 meters. Their top speeds are estimated at 95 to 105 km/h, flying the fastest when in a straight line, though they will fly in a zig-zag pattern when flushed. Their pectoralis muscles, which pull the wings down, make up 24.8% of their body mass. Wilson’s snipes also have been known to swim and dive to avoid raptor predation.

Wilson’s snipes bathe by wading up to their bellies in water and then dipping their beak in the water before using it to preen their breast feathers. They also will touch the tip of their beaks to their uropygial gland before preening themselves vigorously. Wilson’s snipes are terricolous, spending most of their lives on the ground. They are also crepuscular, only active during the twilight hours, and generally sleep standing, usually on one leg with their beaks tucked into the feathers on their backs. When on breeding grounds, they will sleep in vegetation, with their beaks on substrate. Wilson’s snipes also sunbathe by laying on their sides, raising a wing, and spreading their tails. After sunbathing for a period of time, they will shake and switch sides.

Wilson’s snipes will fight both in the air and on the ground. These fights generally occur between two males, but males will occasionally attack females. Fighting consists of fencing with bills, with tails fanned and vertical, until one of the birds gives up and flies away.

Wilson's snipes migrate in order to maintain a food source throughout the year. Because they feed on invertebrates in wetlands, when winter comes, these environments freeze and food is less abundant. They migrate during the night, unless the sun rises while they are over a body of water. In the spring, they return to their breeding grounds.

Wilson’s snipes may be found in small flocks, called wisps, of up to 50 birds during flight. When they land, they tend to leave the flock individually or in small groups, depending on the abundance of food in the area. After mating, Wilson’s snipes form pairs that consist of one male and one female. Once the juveniles are independent, the pair formation of the males and females dissipates, and pairs have no further association. In the face of predators, their primary defense is their cryptic coloration.

• Key Behaviors
• terricolous
• flies
• crepuscular crepuscular
• migratory migratory
• sedentary sedentary
• solitary solitary

Home Range

Mean home ranges average 3.5 square kilometers with a deviation of 0.93 square kilometers in 100% minimum convex polygon (includes all locations in which they have been found) and 1.6 square kilometers with a deviation of 0.42 square kilometers in 95% fixed kernel (includes locations in which they spend 95% of their time). In Canada, Wilson’s snipes are found to have a density between 0.055 pairs per hectare and 12.9 pairs per hectare in sedge bogs; between 3.5 pairs per hectare and 7.2 pairs per hectare in fens; and between 9.5 pairs per hectare and 15.7 pairs per hectare in swamps. Movement and residency do not appear to differ based on sex, though they vary significantly based on season. Wilson’s snipes do not defend a territory.

Communication and Perception

Vocalizations of Wilson’s snipe is restricted to calls. Most calls are vocalized by both sexes. Instances when calls are given by only one sex include aggressive calls by males when encountering a rival male. Mueller (1999) describes three distinct calls made by Wilson’s snipes: the “scaipe”, “chip”, and “chipper.” The “scaipe” is a sudden, hoarse, rasping call only given outside of mating season, generally when the Wilson’s snipes are flushed, migrating at night, or involved in a pursuit flight. The “chip” is a hard, sharp, repetitive call vocalized when the birds are excited or warning their chicks of danger. A “chipper” call is heard during mating season between members of the same sex and to call chicks. Sexual calls are vocalized by males during breeding season when they are landing to entice a female, or by females during breeding season when males pass overhead in flight. The precopulatory calls are rapid clucking that are an extension of the chipper call. Postcopulatory calls are non-sex specific soft whispers. Wilson’s snipes call to their chicks with soft contact calls, hoarse rasps, or soft chirring. These chick calls are used as communication between brooding adults and as a warning that a predator is near. Distraction display calls consist of a variety of grunts, squealing, and wheezing. Chicks call to their mother with soft, quiet calls that quickly escalate to piercing shrills when unattended or frightened.

Wilson’s snipes have eyes that range in diameter from 10-30 mm, depending on age and size. They do not rely heavily on vision for feeding; instead they use more tactile techniques, such as probing and sweeping of their bills.

Wilson’s snipes use their tails to create a unique non-vocal sound known as winnowing. They winnow by spreading their tail feathers and beating the feathers quickly, which creates an audible vibration. This is especially used when diving in flight, when the tail is spread and the airflow creates the vibration needed for sound. This technique is mainly used by males as a show of territorial aggression, but also is used by both sexes to appear as a threat to predators. According to Mueller (1999), winnowing starts becoming audible at airspeeds as low as 39km/h. The winnowing of Wilson’s snipes is higher in frequency and modulation rate (between 700-800 Hz) than that of the common snipe Gallinago gallinago (between 350-400 Hz).

• Communication Channels
• visual visual
• acoustic acoustic

Food Habits

Wilson’s snipes feed primarily in terrestrial and shallow aquatic environments. Food is typically obtained by submerging their beaks, along with their heads and sometimes their entire necks and part of their backs into mud or wet ground and probing until they locate a food source. Wilson’s snipes mainly feed on larval insects and small invertebrates such as craneflies ( Tipulidae ), horse and deerflies ( Tabanidae ), beetles, dragonflies and damselflies, true bugs ( Hemiptera ), ants, mayflies, butterflies and moths, dobsonflies ( Corydalidae ), grasshoppers and crickets, caddisflies ( Trichoptera ), annelids, crustaceans, and gastropods. Plant fibers, seeds, and grit are incidentally ingested while feeding on invertebrates. This is not included in the diet because it remains relatively unchanged by the digestive process and is regurgitated after consumption as a pellet.

Wilson’s snipes’ beaks can open and close without any movement at the base of the beak, which allows for easier consumption of food without removing the beak from the mud. Their beak also is serrated, which aids in moving the food from the tips of their beaks to the back of their mouths, where they can swallow it. In order to startle their prey into moving, they will often stomp the ground to create vibrations.

There are no differences in the feeding habits between the sexes. There is no difference across seasons unless it is especially dry. In these cases they rely on what’s available, flies and beetles.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore

• Animal Foods
• insects
• mollusks
• terrestrial worms
• aquatic or marine worms
• aquatic crustaceans

Predation

Northern harriers Circus cyaneus account for the most predation events of Wilson’s snipes. Other predators include great horned owls Bubo virginianus , peregrine falcons Falco peregrinus , merlins Falco columbarius , northern goshawks Accipiter gentilis , and Cooper’s hawks Accipiter cooperii . When faced with these predators, Wilson’s snipes’ primary defense is their cryptic coloration. They will flush when threats get too close, exploding into flight and attempting to startle the predators. Wilson’s snipes also have been known to dive and fly underwater briefly in order to avoid raptors. Other techniques to avoid predators include snapping their tails open and shut in order to hopefully startle predators, fluttering their wings wildly, and running swiftly while exposing their black spots.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Wilson’s snipes are known to be carriers of Sarcocystis rileyi , which is a protozoan parasite that causes small white cysts in the muscles of the breast, neck, and legs. Endoparasites that use Wilson’s snipes as a host include 36 fluke (Trematoda) species including Cyclocoelum mutabile , Cotylurus cornutus , Echinostoma revolutum , and Pulvinifer macrostomum . Tapeworm (Cestoda) parasites include Hymenolepsis capellae , Haploparaksis filum , Haploparaksis penetrans , Anomotaenia citrus , Choanotaenia cingulifera , and roundworm (Nematoda) species include Cosmocephalus capellae , and Capillaria contorta . Lice ( Actornithophilus stictus , Austromenopon durisetosum , Rhynonirmus emarginatus , Rhynonirmus scolopacsis , Rhynonirmus truncatus , Cummingsiella ambigua , Cummingsiella major , and Cummingsiella nirmoides ) are ectoparasites of Wilson’s snipes.

Economic Importance for Humans: Positive

Wilson’s snipes are a commonly hunted migratory species that are killed for sport and for their meat. It is estimated that the annual numbers of the birds killed each year is between 500,000 and 900,000.

• Positive Impacts
• food food

Economic Importance for Humans: Negative

There are no known negative economic effects of this species on humans.

Conservation Status

Wilson’s snipes are listed as a species of “Least Concern” on the IUCN Red List. They are not given special status on the US Migratory Bird Act, the US Federal List, CITIES, or the State of Michigan List. They are known to be drawn to the flashing lights of lighthouses, radio towers, and television towers, and vehicles. Many flashing white lights are being changed to red as a conservation effort for these and many other bird species. A bacterial threat to Wilson’s snipes is the spirochete Treponema anserinum .

Because Wilson’s snipes are a game species, there is a daily bag limit of 8 snipes across the United States.

Additional Links

Encyclopedia of Life

Contributors

Kristy Clark (author), Radford University, Alex Atwood (editor), Radford University, Marisa Dameron (editor), Radford University, Karen Powers (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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