SPECIES

Bar-tailed Godwit Limosa lapponica Scientific name definitions

Brian J. McCaffery and Robert E. Gill
Version: 1.0 — Published March 4, 2020

Behavior

Locomotion

Walking, Hopping, Climbing, Etc

Occasionally runs after prey (Higgins and Davies 1996), but usually walks between feeding attempts when foraging on submerged substrates, exposed mudflats, or terrestrial meadows. Often runs several steps just prior to take-off. When mildly disturbed, birds roosting on 1 leg may hop away instead of, or prior to, running or flying (BJM, REG).

Flight

Flight normally direct, rapid, and powerful (Higgins and Davies 1996), but several different flight modes used during breeding season (see Sounds: nonvocal sounds, above, and Sexual behavior, below). On nonbreeding grounds, flocks fly in lines, echelons, v-formations, or unstructured clusters or bunches (Piersma et al. 1990b, Higgins and Davies 1996, REG, BJM). May glide on flat or slightly down-curved wings for >100 m when descending from flights above >10 m (BJM, REG). May also use Crazy Flight to descend rapidly onto intertidal feeding or roosting areas (BJM, REG). (For Crazy Flight, see Sounds: nonvocal sounds, above.)

Swimming And Diving

Not known to dive into or from surface of water. Will swim for considerable time in shallow, intertidal water (T. Piersma pers. comm., see Food habits: metabolism and temperature regulation, above).

Self-Maintenance

Preening, Head-Scratching, Stretching, Bathing, Etc

Usually preens, head-scratches, and stretches while roosting. No observation on bathing.

Roosting, Sleeping, Sunbathing

In large roosts, interindividual distance <1 m, frequently ≤0.5 m. On nonbreeding grounds, roosts in flocks (up to thousands of individuals) on upper intertidal flats and shell banks or, at very high tides, inland (Cramp and Simmons 1983, Higgins and Davies 1996); usually on seaward side of other roosting shorebirds and in water, invariably facing into wind (Hale 1980). Time spent at roost a function of tide height, with mean of 2.7 h (range 1.5–4.2) at 1 Great Britain estuary (Hale 1980). In Australia, may occasionally roost among (not on) mangrove trees on coastal islands (I. Fien in Higgins and Davies 1996). Winter flocks in Europe primarily mixed-sex (Smith and Evans 1973). Subadults on nonbreeding grounds during boreal summer remain in flocks (Cramp and Simmons 1983, Higgins and Davies 1996).

On Alaskan staging grounds in late summer and fall, roosting behavior variable. Roosts between low-tide foraging bouts. Roosts monospecific or with other species, including Emperor Goose (Chen canagica); Steller's Eider (Polysticta stelleri); Black-bellied Plover (Pluvialis squatarola); Pacific Golden-Plover (P. fulva); Whimbrel (Numenius phaeopus); Hudsonian Godwit; Western (Calidris mauri), Pectoral (C. melanotos), and Rock sandpipers; Dunlin; Short-billed (Limnodromus griseus) and Long-billed dowitchers, and Bonaparte's (Larus philadelphia) and Glaucous-winged (L. glaucescens) gulls (BJM, REG). In New Zealand, roosting baueri associate with Pied (Haematopus longirostris) and Variable (H. unicolor) oystercatchers, Double-banded (Charadrius bicinctus) and New Zealand (C. obscurus) dotterels, Red Knot (Calidris canutus), Ruddy Turnstone (Arenaria interpres), Whimbrel, Far Eastern Curlew (N. madagascariensis), and Black-tailed Godwit (REG). In Alaska, roosting flocks may vary from several individuals to several thousands. Larger flocks usually monospecific (except at island roosts), but on mudflats, may be within 10 m of (but separate from) large roosts (thousands) of Dunlin. Smaller, multispecies flocks usually away from immediate vicinity of coast (BJM). Sexes roost together, but juveniles may be segregated, occurring either at periphery of (or, less frequently, within) mixed-age flocks or in separate juvenile flocks. Roost sites usually exposed mudflats, occasionally in shallow areas inundated by incoming tide, or on barrier islands, especially among estuaries of Alaska Peninsula (BJM, REG). Before water level reaches ankles, birds depart for higher roost sites on exposed mudflats, islands, or inland meadows. Inland habitats include salt-grass or dwarf-shrub meadows a few hundred meters to several kilometers from shore (Gill and Handel 1990); use of inland sites does not always correspond to magnitude and/or timing of tidal maxima (BJM). During receding tides, godwits may leave high-tide inland roosts and roost temporarily on earliest exposed mudflats before departing to feed farther out later in tidal cycle (BJM). Similarly, during incoming tide, godwits may roost on exposed flats near low-tide line before moving to roosts on inner mudflats and/or inland meadows (REG, BJM). Fidelity to roost sites variable; some sites used up to 11 consecutive days (REG). Roost sites often vary among days, between consecutive tidal cycles, and even within single tidal cycle (BJM). For example, at Kigigak I. on Yukon-Kuskokwim Delta, godwits regularly roosted inland at or near 10 isolated uplands that were separated by hundreds of meters. Godwits roosted at same upland site on consecutive days during only 13 of 50 (26%) high-tide censuses; even among these 13, 10 involved habitat switches between dwarf-shrub uplands and surrounding sedge meadows (BJM). Timing of departures to and from roosts also varied at Kigigak. Relative to time of high tide, 8 departures for inland roosts from mudflats varied by 54 min; width of intertidal mudflat exposed at time of departure ranged from 75 to 550 m. Departures from inland roosts en route to mudflats (n = 11) varied by 2.4 h, and width of exposed intertidal mudflat upon arrival ranged from 40 to 710 m (BJM). Spooks (see Predation, below) by falcons (Falco spp.) and Parasitic Jaegers (Stercorarius parasiticus) frequently trigger departures from feeding areas to roosts (and vice versa), as well as relocations among roosts (BJM). See Demography and populations: range, below.

Sleeps with head facing posteriorly, bill tucked beneath scapulars, often while standing on 1 leg. No information on sunbathing.

Daily Time Budget

Quantitative data limited for baueri . Birds staging at w. Alaska estuaries foraged 6–10 h/low tide depending on stage of lunar cycle; during moderate tides (both high and low), foraging of some birds extended throughout 12-h cycle (REG, BJM). In Australia, putative baueri reported to feed 5.5 h of tidal cycle (Dann 1979). In Europe, individuals (lapponica) feed 4–6 h about low tide (Evans 1976b). At German Wadden Sea during spring migration, taymyrensis spent more time (51%) feeding during tidal cycle than did lapponica (31%), more time in loco-motion, and about same time preening and inactive (Scheiffarth and Ketzenberg 1993). At Banc d'Arguin, Mauritania, godwits increased daily (daylight) time spent foraging/low-water cycle from 65% in Feb to 83% in Mar and 90% (about 7 h) in Apr just before northward departure; at night, also fed 5–6 h during each low-water cycle throughout Mar and Apr (Zwarts et al. 1990b). In coastal lagoons in Ghana, godwits spent 74% of daylight hours foraging, 21% roosting, and 5% in comfort activities; also recorded feeding at night, but time not quantified (Ntiamoa-Baidu et al. 1998).

Agonistic Behavior

Physical And Communicative Interactions

Aggression on breeding grounds relatively infrequent, but in wide range of contexts. Byrkjedal et al. (Byrkjedal et al. 1989) identify 4 aggressive behaviors between individuals on the ground: Erect Threat, Forward-bent Threat, Flutter-Jumping, and Ground Chases. In Norway, latter only performed by males (Byrkjedal et al. 1989), but in Alaska, Ground Chases (with terminal bill thrust) may be directed by foraging females toward mate, if foraging too closely, or toward courting male (not her mate) during her incubation break (BJM).

Four additional stereotyped behaviors observed in Alaska (BJM): (1) Bow—1- to 2-s-long display in which godwit tilts forward with bill and neck only. Bow uniformly paced from initial Bow to resumption of erect posture. No pause at bottom of bow; back and tail held horizontally throughout (latter 2 characteristics separate Bow from Forward-bent Threat). (2) Spread-winged Rush—Usually approaching from side or rear, aggressive bird runs toward or past rival with wings spread to side; occasionally, wings slightly elevated above plane of body. In this behavior, aggressor may briefly take flight just past (but not at) rival; usually causes rival to flinch, and in 1 bout, >90% of 115 rushes resulted in displacement of rushed bird. (3) Parallel Walking—Two males walk forward 1–2 m apart (side by side or 1 ≤0.25 m ahead of other) for ≤2 m before pausing in Erect Threat; in extended bouts, pauses in Erect Threat longer than intervening Parallel Walkings. (4) Pot-bellied Walk—Aggressive bird walks in slight crouch directly toward intruder while assuming exaggerated posture in which belly seems very rounded and distended downward, head and neck remain upright, and tail may or may not be cocked. This behavior rare, only seen twice, both on outer Yukon-Kuskokwim Delta; aggressor displaced neighbor both times. Ground displays involving Erect Threat, Forward-bent Threat, Bow, Ground Chase, Spread-winged Rush, and Parallel Walking may escalate into physical fights in which Flutter-Jumping males attempt to mount rivals. Forward-bent Threat often triggers Flutter-Jumping (Byrkjedal et al. 1989, BJM). Mounting male hammers dorsal surface of pinned male with bill (BJM). In 1 case, defending male repeatedly used Ground Chases to flush an intruder; intruder responded by taking flight 1–2 m ahead of and above defender, then caught wind to blow back toward rival. When intruder descended directly over defender, latter bird used Flutter-Jumping to avoid being mounted (BJM). Usually silent during such conflicts; Basic Calls and Rapid Calls rare. Agonistic bouts between displaying males may exceed 30 min (Yésou et al. 1992, BJM).

Aggression by flying godwits may be directed at individuals either on ground or in flight. Former class of aggression includes unpaired males displacing other males from display area, paired males chasing unpaired males from vicinity of mates, and males disrupting copulations (C. Harwood pers. comm., BJM). In-flight aggression usually involves 2 males, either flying alone or in presence of female. In absence of females, male-male aggression includes both simple chases and stereotyped Parallel Flights. Latter behavior involves 2 males flying side by side approximately 1 m apart, often ≤1 m above ground, careening wildly back and forth over distances of up to several hundred meters. Parallel Flights may punctuate extended bouts of ground displays or result in birds ultimately diverging; males leaving Parallel Flights may initiate Ceremonial Flight (see Sexual behavior, below). Males occasionally fly to chase passing pairs involved in either Pursuit Flights (sensu Byrkjedal et al. 1989) or joint Ceremonial Flights (see Sexual behavior, below). In some cases, second male chases pair, then returns to original site (Byrkjedal et al. 1989); in others, particularly if approaching male gets between members of pair, paired male chases, and may actually strike, intruding male (BJM). Unpaired males may return from such conflicts in Ceremonial Flight (Byrkjedal et al. 1989, BJM).

Bar-tailed Godwits exhibit marked variation in spatial extent and coloration of breeding plumage (Nelson 1887a, Conover 1926, Brandt 1942), but function poorly understood. Extent and quality of breeding plumage might allow godwits to assess quality of potential mates, with more richly colored males of higher quality than pale males (Piersma et al. 1993b; see also Demography and populations: disease and body parasites, below). In w. Alaska, however, all 3 interactions between males at extremes of Piersma and Jukema's (Piersma and Jukema 1993) color scale (i.e., “light rufous” versus “rusty red”) resulted in light male repeatedly supplanting and/or chasing off dark male (BJM).

Away from breeding grounds, agonistic behavior usually limited to short bill thrusts toward encroaching neighbors in dense foraging and roosting flocks (BJM). In Netherlands Wadden Sea, fall migrant female godwits kleptoparasitic on foraging males (C. Both unpubl.). In defense of feeding sites (interspecific or intraspecific not specified) in Gdansk Bay, Poland, godwits spread wings and lowered tail if intruder approached from behind or lowered breast and cocked tail if threat from front (Stawarczyk 1984).

Spacing

Territoriality

Not well defined among breeding godwits in general (e.g., Hagar 1966), and apparently weak in Eurasian populations of this species, where aggressive reaction distances may be <2 m (Kondratiev 1982, Byrkjedal et al. 1989). In Alaska, observations equivocal. Diverse, ritualized ground and aerial interactions between males, lengthy fights (see Agonistic behavior, above), and males chasing both males and pairs away from specific meadows seem analogous to portions of behavioral repertoires used by other species of territorial scolopacids. Other observations, however, not consistent with classic territoriality. Early in breeding season, males drive away some intruding males from specific meadows, yet on same day in presence of female, same defending males tolerate other males only a few meters away. Ceremonial Flights (see Sexual behavior, below) by unpaired males frequently performed above meadows occupied by courting, egg-laying, and/or incubating pairs; both male-male chases and single-male Heterosexual Flights (see Sexual behavior, below) may range over >1 km above habitats occupied by multiple intervening pairs; and male Parallel Flights (see Agonistic behavior, above) do not seem limited to borders between territories, but instead range widely and erratically across tundra (BJM). These observations suggest that dispersion of breeding birds across suitable habitat is not established and/or maintained in same manner (e.g., persistent, spatially fixed display flights; aerial patrols of borders) as other large shorebirds with which they are sympatric (e.g., Black-bellied Plover, Whimbrel, Bristle-thighed Curlew [Numenius tahitiensis]; BJM). Spatial extent, temporal persistence, and seasonality of defended areas in breeding Bar-tailed Godwits need additional study.

Although breeding males are frequently aggressive toward other species (see Social and interspecific behavior, below), no evidence for interspecific territoriality. Away from breeding grounds, territoriality reported (but not defined) among southbound migrants in Poland (Stawarczyk 1984).

Densities on the breeding grounds typically range between 0·1–1·0 pairs/km².

Individual Distance

Distances between foraging birds in staging flocks on Bering Sea coast of Alaska range from <1 m to dozens of meters. Both on and away from breeding grounds, and among both foraging and roosting birds, godwits approaching conspecifics within 0.5 m occasionally dissuaded from closer approach by rapid bill thrust from approached bird (BJM). See Agonistic behavior, above.

Sexual Behavior

Mating System And Sex Ratio

Presumably monogamous (Cramp and Simmons 1983), based on season-long pair-bonding with biparental care (Byrkjedal et al. 1989, Larsen and Moldsvor 1992; see below), but paternity analyses lacking. On Mauritanian wintering grounds, sex ratio skewed strongly toward males; perhaps on European spring staging areas as well (Piersma et al. 1993b). Sex ratio on breeding grounds, at least early in breeding season, also apparently male-biased; unpaired males display regularly through period of peak pairing and egg-laying in Scandinavia, Siberia, and Alaska (Byrkjedal et al. 1989, Yésou et al. 1992, BJM).

Pair bond. Courtship displays and mate-guarding. Three classes of courtship displays: Ceremonial Flights, Heterosexual Flights, and Ground Displays. Ceremonial Flights primary context for Song (see Sounds: vocalizations, above) and performed exclusively by males (although female in normal flight may accompany displaying male). These flights consist of 5 phases: (1) Ascent, (2) Limping Flight, (3) Horizontal Gliding, (4) Descent, and (5) Landing (Byrkjedal et al. 1989). Five phases of Ceremonial Flights common to all Limosa, although Limping Flight may be replaced or supplemented by circling and/or tumbling in other species (Hagar 1966, Nowicki 1973, Cramp and Simmons 1983, Mehall-Niswander 1997); style and prevalence of Horizontal Gliding variable both between and within Limosa species (e.g., not observed in Bar-tailed Godwit in Alaska; BJM).

Ascent to Ceremonial Flight display altitude in 1 of 4 modes: (1) normal flight ascending over horizontal distance of 50–200 m before leveling out for Limping Flight (rarely up to 400 m of low-level flight prior to ascent; BJM), (2) pivoting flight (slow, deliberate wing beats with pivoting tail and leg movements), (3) take-off in Flutter-Hover (body posture similar to Byrkjedal et al.'s [Byrkjedal et al. 1989] fluttering courtship, with head and bill up, neck forward and partially erect, ventral surface distended and rounded as in Pot-bellied Walk [see Agonistic behavior, above], with wings fluttering slowly over male's back; forward progress very slow), transition to normal flight, then ascending Limping Flight, or (4) take-off and climb in silent Limping Flight. Ascent modes “a” and “b” reported from Norway (Byrkjedal et al. 1989); all 4 in Alaska (BJM). In Limping Flight, male alternates tilting from right to left with 3–7 wing beats per side-tilt; flashing effect of silvery-white underwings contrasting with reddish ventrum apparently important for signaling (I. Byrkjedal pers. comm.). In Norway, Limping Flight accompanied by continuous Song, at altitude of >30 m, punctuated by intervals of Horizontal Gliding (Byrkjedal et al. 1989); in Alaska, Limping Flight often without, or with only intermittent, Song, at altitudes from ≤15 to ≥200 m, and punctuated by Nose-dive rather than Horizontal Gliding (BJM). In Norway, displaying godwit descends via 45–90° nose-dive (see also Sounds: nonvocal sounds, above), a spread-winged glide with neck curved back, or a spiraling descent (Byrkjedal et al. 1989). Alaskan birds use both Nose-dive and spread-winged glides, as well as a combination of 1 or 2 dives before a final gliding descent (BJM). Nose-dives also punctuate Limping Flight, therefore possibly analogous to tumbling flight of Black-tailed Godwit (Cramp and Simmons 1983). During single Ceremonial Flights, male may Nose-dive 1–3 times prior to final descent. Nose-dives during Ceremonial Flights may be directed at other species (see Social and interspecific behavior, below). Terminal descents via Nose-dive often accompanied by audible braking (see Sounds: nonvocal sounds, above); after leveling off, male often glides for dozens of meters (<1 m above ground) before landing. Landing often, but not always, accompanied with extended raised wings (1–2 s) before folding (Byrkjedal et al. 1989, BJM). During some bouts of Ceremonial Flights early in pair-bonding process, male always lands in raised-wing posture facing female; silvery ventral surface of male's flight-feathers very conspicuous (BJM).

Two types of Heterosexual Flights, multimale and single-male. Multimale flights involve 2 males led on rapid, erratic chase by female (BJM). Distinguished from in-flight aggression (see Agonistic behavior, above) in that both males are clearly chasing female rather than one another. Function of multimale Heterosexual Flights unknown, usually occur prior to or during egg-laying; may allow female to evaluate suitors. Alternatively, these flights may simply be females (perhaps already paired or even incubating) trying to avoid unwanted courtship while en route to or from nesting area (BJM).

Single-male Heterosexual Flights (including Byrkjedal et al.'s [Byrkjedal et al. 1989] Pursuit Flight) always involves a pair of birds (i.e., male and female), but otherwise extremely variable (BJM). Variation includes flight path (straight or sinuous), flight leader (male, female, or neither [i.e., pair flying parallel]), flight mode (normal wing beats, Flutter-Hover, Arc-winged Glide, or Lazy Flight; for latter 2, see descriptions below), flight posture of male (normal, Pot-bellied, or Extended [see description below]), and vocalization (by male, female, or neither). In Arc-winged Glide, wings outstretched (i.e., roughly parallel to ground) and held steady above plane of body with decurved wing-tips. Observed only twice on Yukon-Kuskokwim Delta, once involving a pair and once male only. In Lazy Flight, wing beats slow and languid relative to normal flight. In Extended Flight, male's head, neck, and bill are extended in a straight line angled approximately 30° above plane of body. Extended Flight used in conjunction with both normal flight and Arc-winged Glide; in latter context, elevated head and bill still below arc of wings (BJM).

In Norway, single-male Heterosexual Flights involve vocalizing males following females over a sinuous flight path (“Pursuit Flights”; Byrkjedal et al. 1989). In Alaska, multiple permutations involving variation described above, but typical pattern includes low-level (i.e., 1–4 m high) sinuous flight path, silent males in Extended Flight posture (female posture normal) leading flight with both birds using normal wing beats. Within single flight, however, male may engage in up to 3 flight modes (BJM). Observations on breeding grounds too limited to determine significance of variation in single-male Heterosexual Flights.

Ground Displays include Nest-Scraping, Nest-Scrape Showing, Erect Courtship, Fluttering Wings-High, and Crouching Courtship (Byrkjedal et al. 1989). Nest-Scraping and Nest-Scrape Showing typically performed by males (Byrkjedal et al. 1989), but 1 female in Andreafsky Wilderness (Yukon-Kuskokwim Delta) performed both and attracted male to scrape (BJM). Nest-Scraping often extensive early in pair-bonding; Alaskan male on first day of courtship performed 5 bouts of Nest-Scraping, totaling 28.5 min in a 74-min span of continuous observation (BJM). Female may or may not respond to male Nest-Scraping. As in Black-tailed and Marbled godwits (Nowicki 1973, Cramp and Simmons 1983), male Bar-tailed Godwit performs sideways-building and throwing (i.e., picking nest-lining material from immediate vicinity of nest and tossing over shoulder into scrape from sitting and standing positions, respectively); like Marbled Godwit, Bar-tailed Godwit shifts orientation while scraping by rotating in cup (BJM). Male may give faint calls while in scrape (see Sounds: vocalizations, above). Fluttering Wings-High may lead to Flutter-Hover, in which male flies slowly <1 m above ground ahead of female for several seconds, apparently as enticement to single-male Heterosexual Flights (BJM); probably analogous to quiver flight of Black-tailed Godwit (Cramp and Simmons 1983). In Andreafsky Wilderness, paired female on incubation break ignored Flutter-Hover display by unpaired male and continued feeding; unpaired female took flight and followed suitor (BJM).

Mate-guarding not confirmed, but single-male Heterosexual Flights and male-male chases in presence of females (see Agonistic behavior, above) probably serve this function, at least in part (BJM).

Copulation. In most extensive precopulatory display, male performs “tilted” Flutter-Hover with plane of bill, head, and body at 45° to ground and flies slowly past female. If flying upwind, he may let wind catch him, drift back toward female, and ease to landing approximately 1 m away from her. Male approaches female in slight crouch with mincing gate while in Erect Courtship posture (i.e., tail cocked above folded wing-tips, back level, pot-bellied, head up, and bill tilted slightly upward). If female walks away, male may follow in this mode for >1 min; if she stops, he steps behind her and begins Fluttering Wings-High (but without cocked tail) and calls (see Sounds: vocalizations, above). Male continues Fluttering Wings-High while prancing from side to side behind female, describing arc of approximately 120° centered on female. If she remains, male begins marching in place directly behind her. Up to 20 s after start of Fluttering Wings-High, male lifts off in Flutter-Hover, flies forward and descends slowly onto female's back, gradually easing on to his tarsi, while he continues fluttering wings and calling. Mounting may last >40 s, with up to 8 cloacal contacts during a single bout (BJM). Female may walk or run out from under male during mounting; male may either land (ending bout) or maintain hover for several seconds, remount, and copulate again (Byrkjedal et al. 1989, BJM). Postcopulatory displays not reported; female may immediately preen undertail coverts (BJM). Precopulatory displays may be abbreviated or even eliminated; after chasing off rival, male may return and mount female directly (Byrkjedal et al. 1989, C. Harwood pers. comm.). In Andreafsky Wilderness, 1 observation each of male disrupting copulation of neighboring male (C. Harwood pers. comm.) and mounting by paired male in presence of 2 additional pairs and 2 solo males on riparian mudflat prior to dispersal onto breeding habitat in early spring (BJM).

Duration and maintenance of pair bond. In Norway and Taimyr, some birds paired upon arrival (Larsen and Moldsvor 1992, Yésou et al. 1992). In Alaska, spring observations of pairs flying north over Yukon-Kuskokwim Delta, copulation attempts prior to occupation of nearby nesting habitat (see Copulation, above), and pairs in breeding habitat up to 5 d prior to onset of courtship displays all suggest some pairing occurs prior to arrival on breeding grounds (BJM). Pair bond persists into, and at least occasionally through, fledging of young (Conover 1926, Gabrielson and Lincoln 1959, Piersma et al. 1996c, REG, BJM).

Extra-Pair Mating Behavior

Occurs in other Limosa (e.g., Black-tailed Godwit; Byrkjedal 1985a), but not documented in Bar-tailed Godwit.

Social and Interspecific Behavior

Degree Of Sociality

Ranges from solitary adults foraging while off duty during nesting season to flocks of thousands feeding and roosting together away from breeding grounds (see also Self-maintenance, above). Flock size varies seasonally on Yukon-Kuskokwim Delta. Spring flocks usually small at Kanagayak, 20–25 km inland from Bering Sea coast (BJM). In second week of May, median flock size of arriving migrants (i.e., those apparently settling in local breeding habitat) is 2 (range 1–50, n = 55); in latter half of May, median flock size of passage migrants (i.e., later wave of northbound birds) is 7 (range 1–26, n = 21). Flocks of ≤200 roosting/feeding birds at Tutakoke River along immediate coast early in fourth week of May; by end of first week of Jun, flock size ≤150 (REG). By end of fourth week of Jun, however, arrival of failed breeders and/or nonbreeders along coast produces flocks of ≤500 (REG). Postbreeding flocks continue to grow throughout summer and early fall on coastal staging grounds, peaking in early Sep with single flocks up to 7,000 individuals (REG, BJM).

Departure of foraging Bar-tailed Godwits from mudflats to adjacent berry patches usually initiated by 1 or a few individuals, but remainder of flock usually follows within 20–30 s (McCaffery 1998b). First arrivals on mudflats recently exposed by receding tide may be solitary, but usually flocked (BJM). Departures from outer mudflats during rising tide rarely synchronous; staggered departures of flocks of tens, hundreds, or thousands from incoming tide line may span several hours (BJM).

Play

Not reported. Crazy Flight by solitary individuals (see Sounds: nonvocal sounds, above) suggests behavior might have “play” function.

Nonpredatory Interspecific Interactions

In w. Alaska, regularly associates with other species in migration, while feeding, and in roosts (for latter, see Self-maintenance, above). During spring migration on Yukon-Kuskokwim Delta, some arriving flocks seen with Black-bellied Plovers, Black Turnstones (Arenaria melanocephala), and/or Long-billed Dowitchers; flocks of passage migrants exclusively monospecific (BJM). Foraging birds using coastal meadows in early spring associated with several species; most frequently Red Knot, Pectoral Sandpiper, Dunlin, Long-billed Dowitcher, and Red-necked Phalarope (Phalaropus lobatus), but particularly during first few days after arrival, also with Black-bellied Plover, Ruddy and Black turnstones, and Western and Rock sandpipers (BJM, REG). Occasionally forages on lake-bottom ice that has floated to surface in early spring; in addition to most shorebird species with which it forages in meadows, godwits may share same sheet of ice with waterfowl, cranes, and gulls. On Seward Peninsula breeding grounds, recent spring arrivals in upland meadows may forage with American (Pluvialis dominica) and Pacific golden-plovers and Bristle-thighed Curlew. Once incubation is under way, failed or off-duty breeders may join similar flocks of up to 18 Bristle-thighed Curlews (REG). Observed foraging with Whimbrel on Colville River delta (M. North pers. comm.).

During postbreeding period in Alaska, foraging birds on coastal mudflats occasionally associate with Hudsonian (Kessel and Gibson 1978, McCaffery and Harwood 2000) or Marbled godwits (Gibson and Kessel 1989). More frequently found with or near Black-bellied Plover, Red Knot, Dunlin, and, occasionally, Whimbrel (BJM, REG). May form monospecific flocks (McCaffery 1998b) or join with other large shorebirds when foraging on berries in uplands, including Black-bellied Plover, Pacific Golden-Plover, Whimbrel, and Hudsonian Godwit (McCaffery and Harwood 2000, BJM). Flock of 2 Bar-tailed and 1 Hudsonian godwits performed simultaneous Crazy Flight (see Sounds: nonvocal sounds, above) over Kigigak I., Yukon-Kuskokwim Delta (BJM). Southbound migrants at same site seen with Hudsonian Godwits (McCaffery and Harwood 2000). In Africa, L. l. lapponica departs on migration in flocks with Eurasian Curlews and Whimbrels (Piersma et al. 1990b) and occasionally with Red Knots in New Zealand (Battley 1997).

In w. Alaska, males in Ceremonial Flight frequently interrupt Limping Flight to Nose-dive (see Sounds: nonvocal sounds, above) at other species, including Western Sandpiper, Common Snipe (Gallinago gallinago), Red-necked Phalarope, Short-eared Owl (Asio flammeus), and Lapland Longspur (Calcarius lapponicus). Momentum of Nose-dive may result in parabolic trajectory as godwit swoops out of dive, while species being chased is often driven into ground with crash-landing. Alternatively, godwit may level off from Nose-dive near ground and chase other species in normal flight for ≤30 s before ascending again to continue Limping Flight (BJM). Males in Ceremonial Flight may also interrupt display to chase other species in normal flight without Nose-dive (REG). In n. Alaska, American Golden-Plover, Semipalmated Sandpiper (Calidris pusilla), and Sabine's Gull (Xema sabini) chased by displaying males (P. Miller pers. comm.). In New Zealand, seen to chase and bill-thrust at foraging Black-tailed Godwits (A. Riegen pers. comm.).

Forms brood aggregations with other species of shorebirds, including Black-bellied Plover, American and Pacific golden-plovers, Whimbrel, Bristle-thighed Curlew, and Dunlin, as well as Long-tailed Jaeger (Stercorarius longicaudus; Lanctot et al. 1995, Gill et al. 1996a, K. Moitoret pers. comm., BJM), and may nest near other species that attack-mob predators (see Predation, below). On Norwegian breeding grounds, Whimbrels attacked and drove off Bar-tailed Godwits in 38% of cases when foraging individuals of the 2 species came within 35 m of one another (Larsen and Moldsvor 1992). Similar interactions seen on Seward Peninsula and in Andreafsky Wilderness, AK (REG, BJM). Also in Alaska, both Bristle-thighed Curlews and Whimbrels occasionally chase Bar-tailed Godwit pairs; conversely, female Bar-tailed Godwit once chased Bristle-thighed Curlew >300 m (REG), and a male near its brood ground-chased a silent Bristle-thighed Curlew standing nearby (BJM). On Yukon-Kuskokwim Delta, 1 observation of Black-bellied Plover attack-mobbing Bar-tailed Godwit as latter flew through plover's territory; godwit did not accelerate or change flight path in response to plover's diving attacks (BJM).

Predation

Kinds Of Predators, Manner Of Predation

Documented instances of predation or attempted predation rare. Predator diets, known predators of sympatric shorebirds of comparable size, and Bar-tailed Godwit responses to potential predators (see below), suggest godwit adults probably most vulnerable to raptors (primarily Circus, Buteo, and Falco), foxes (including red fox [Vulpes vulpes] and arctic fox [Alopex lagopus]), and weasels (Mustela spp.); eggs and/or chicks vulnerable to same, as well as corvids, gulls, jaegers (Larsen et al. 1996), and Sandhill Cranes (Grus canadensis; BJM). Known target of Gyrfalcons (Falco rusticolus; Cramp and Simmons 1983); found in prey remains at Peregrine Falcon (F. peregrinus) and Rough-legged Hawk (Buteo lagopus) eyries along Colville River, AK, but rare in diet of latter species (only 2 of 1,065 prey items; T. Swem pers. comm.). Also in Peregrine Falcon eyrie on Yamal Peninsula, Siberia (Danilov et al. 1984). Identified only twice among food items from long-term study in n. Alaska of all 3 jaeger species (Maher 1974c). In New Zealand, Harrier (Circus approximans) only bird of prey in coastal areas, and godwits always take flight in its presence; Harrier-killed godwits found near roosts (A. Riegen pers. comm.). In Mauritania and Great Britain, wintering godwits usually not preyed on by large falcons, though latter common and source of mortality for numerous other species of shorebirds (Bijlsma 1990, Cresswell and Whitfield 1994; for exception, see Piersma and Baker 2000).

Response To Predators

Nest-site selection at landscape and local scales may be mediated by presence of species that attack nest predators and provide “protective umbrella” for Bar-tailed Godwits (Larsen and Moldsvor 1992). In Norway and Alaska, range of this species overlaps that of ≥1 attack-mobbing species, including Black-bellied Plover, Whimbrel, Bristle-thighed Curlew, and Long-tailed Jaeger (Larsen and Moldsvor 1992, BJM). Locally, Bar-tailed Godwits nest near Whimbrel (Larsen and Moldsvor 1992) and/or Long-tailed Jaeger at some sites (Maher 1959, Kondratiev 1982, H. Popham in Cramp and Simmons 1983, Larsen and Grundetjern 1997, BJM), but not others (Yésou et al. 1992). Nests later than other attack-mobbing species (Whimbrel in Norway, Long-tailed Jaeger in n. Alaska), and nests are closer to nests of these species than predicted by chance or models of habitat choice (Larsen and Moldsvor 1992, BJM). Both suggest this godwit selects nest sites near other attack-mobbers. Presumed costs and benefits of these nesting associations require more rigorous study (R. Lanctot pers. comm.).

Employs array of predator-defense tactics. At nest, incubating bird sits tight (Conover 1926, Cramp and Simmons 1983, Larsen and Moldsvor 1992). In response to human, mean nest-flushing distance 11 m in Norway (Larsen and Moldsvor 1992), but frequently much closer (<2 m) in Alaska (BJM). Flushed adult may feign injury (Brandt 1942, Yésou et al. 1992, J. Dorio pers. comm.). Around eggs and young, may perform Approach Flights, Scolding from the ground and in flight (including Quivering Scolding Flight; see Cramp and Simmons 1983 for description in Black-tailed Godwit), Agitated Circling, and Mobbing (behaviors sensu Gochfeld 1984; BJM). May approach and scold predators 300–500 m from nest and “escort” them comparable distances away from nest; incubating adult often leaves nest and joins sentinel in scolding and/or circling predator (Yésou et al. 1992, BJM). Same behaviors occasionally given by unmated males (Yésou et al. 1992). Most potential predators (including humans and dogs) elicit Approach Flights and/or Scolding. Agitated Circling seen in response to Gyrfalcon, Peregrine Falcon, Parasitic Jaeger, and Common Raven (Corvus corax; REG, BJM).

Attack-mobbing highly variable. Reported by most Alaskan observers (e.g., Nelson 1887a, Gabrielson and Lincoln 1959), but rare or absent at some sites in Eurasia (Larsen and Moldsvor 1992). In Alaska, consistently attack-mobs avian predators, but response to humans variable; some birds and/or populations exhibit no attack-mobbing of humans (BJM), whereas others do (Nelson 1887a, Gabrielson and Lincoln 1959). Attack-mobbing occurs throughout breeding season from prelaying to postfledging (Conover 1926, Gabrielson and Lincoln 1959, Larsen et al. 1996, BJM). Dur-ing incubation, attack-mobbing performed only by off-duty (i.e., nonincubating) adult (Conover 1926, Larsen and Moldsvor 1992) or by both parents (BJM). During brood-rearing, male or female may respond first and/or approach intruder most closely while Scolding (BJM).

In Alaska, attack-mobs Northern Harrier (Circus cyaneus), Rough-legged Hawk, Golden Eagle (Aquila chrysaetos), Sandhill Crane, Parasitic and Long-tailed jaegers, Glaucous Gull (Larus hyperboreus), and Common Raven. Rarely, attack-mobs mammals, including red fox (P. Miller pers. comm.) and arctic ground squirrel (Spermophilus parryii; BJM). Proximate effects of attack-mobbing by this godwit include distracting predator, causing ground predators (e.g., cranes) to flinch or duck, and causing course corrections and/or acceleration out of nesting area by aerial predators (BJM).

During incubation and brood-rearing, may join other species, including Black-bellied Plover, Bristle-thighed Curlew, Whimbrel, Long-tailed Jaeger, and Mew Gull (Larus canus), in attack-mobbing. After hatch, these groups frequently result of interspecific brood amalgamation (Lanctot et al. 1995; see also Social and interspecific behavior, above). Multispecies aggregations including Bar-tailed Godwits observed throughout species' range in Alaska (Lanctot et al. 1995, Gill et al. 1996a, K. Moitoret pers. comm., BJM). Age composition of godwits in brood aggregations ranged from 9 adults and 3 young to 2 adults and 10 young (Lanctot et al. 1995). Brood aggregations with joint defense presumably enhance predator defense and may allow some parents to desert their young earlier (Lanctot et al. 1995).

When disturbed at nest, newly hatched young may scatter and hide (Cramp and Simmons 1983); out of nest, chicks crouch and/or run when predator approaches (BJM).

Away from breeding grounds, associates in flocks, presumably for predator defense. When approached by avian predators, flocks “spook” (i.e., flush, coalesce, and wheel erratically) until predator has passed. In w. Alaska, fall flocks spook in response to Northern Harrier, Northern Goshawk (Accipiter gentilis), Gyrfalcon, Peregrine Falcon, and Parasitic Jaeger (BJM). At Kigigak I. on Yukon-Kuskokwim Delta, 22 of 26 spooks (85%) triggered by Parasitic Jaegers; however, jaegers never observed targeting godwits when attacking shorebird flocks (BJM).

Recommended Citation

McCaffery, B. J. and R. E. Gill (2020). Bar-tailed Godwit (Limosa lapponica), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.batgod.01