Welcome to the Birds of North America Online!
Welcome to BNA Online, the leading source of life history information for North American breeding birds. This free, courtesy preview is just the first of 14 articles that provide detailed life history information including Distribution, Migration, Habitat, Food Habits, Sounds, Behavior and Breeding. Written by acknowledged experts on each species, there is also a comprehensive bibliography of published research on the species.
A subscription is needed to access the remaining articles for this and any other species. Subscription rates start as low as $5 USD for 30 days of complete access to the resource. To subscribe, please visit the Cornell Lab of Ornithology E-Store.
If you are already a current subscriber, you will need to sign in with your login information to access BNA normally.
Subscriptions are available for as little as $5 for 30 days of full access! If you would like to subscribe to BNA Online, just visit the Cornell Lab of Ornithology E-Store.
Nonsocial behaviors described by Ellis et al. (1991); social behaviors by Ellis et al. (unpubl. data).
Walking, Hopping, Climbing, Etc
Ambulatory behaviors in cranes are termed Waddle, Walk, Run, Hop, Leap, and transitional actions such as Run-flap, Alight, Pre-flight-posture, Wing-spread-hold, and Spring-up (Ellis et al. 1991). Waddle, infrequent, involves a bird sitting and walking on its tarsi; seen in chicks or incubating adults. Hop is seen in a bird with an injured leg or moving short distance while standing on 1 leg. In general, Whooping Cranes move with a smooth, stately elegance, giving the appearance of effortless gliding, legs straight, head and neck erect and rather stiff.
Includes flapping, soaring, gliding, and downward-gliding, which precedes alighting. Flapping flight involves shallow flaps. Soaring and gliding are combined in long flights in migration. Soaring is rising on updraft in circular pattern followed by gliding in 1 direction with a gradual decrease in altitude. Mean flight speed in migration 53 km/h and wind-assisted flight >100km/h (Kuyt 1992). See also Migration: migratory behavior.
Swimming And Diving
Swimming is most common in chicks and involves floating and leg-paddling. Whooping Cranes do not dive in water.
Preening involves using the bill to Nibble plumage in a combing motion or stroke the feather surface. Whooping Cranes are not known to “feather paint” in the manner of Sandhill Cranes. They use the middle toe to scratch the head and neck, and they may rub inverted head (Head-rub) on the back or wing to relieve an itch, clean the head, or distribute uropygial oil (Ellis et al. 1991). Comfort movements include the Head-shake, Ruffle-shake, Shiver-shake, Wing-shake, Tail-shake, Tail-wag, Yawn, One-leg-stretch, Side-stretch, Two-leg-stretch (raising the rump), Two-wing-spread-stretch, Bow-stretch, Rise-flap, Wing-fold, and Leg-flick (Ellis et al. 1991). Bathing may include a side-to-side thrashing of the submerged bill, plunging the head and neck in and out of the water, thrashing the submerged wings, and immersing most of the body (Walkinshaw 1973, Ellis et al. 1991).
Sleeping And Roosting
Whooping Cranes do not perch in trees. Very young chicks (1 d old) sleep with head on ground. Small chicks roost overnight on nest, older chicks on small islands or clumps of vegetation. Observations in captivity indicate that water roosting by standing on 1 leg may not occur until young fledge. Adults doze with bill downward on neck or sleep with bill resting on back. If feeding in uplands, they move to water’s edge about dusk and into water at dark. Older birds stand (roost) in water 13–20 cm deep, presumably to provide nighttime security from nocturnal predators, and remain there until daybreak.
Daily Time Budget
Time budgets not available from nesting grounds of Aransas/Wood Buffalo population. Time budgets of migrants from this population at staging areas: foraging 41.4% of daylight, agonistic 0.1%, standing 12.7%, alert 10.6%, walking 10.9%, flying 2.1%, Dancing 0.3%, preening 10.7%, resting 2.8%, other 0.7%, and no data 8.2% (Howe 1989). On wintering area, Aransas/Wood Buffalo birds exhibit differences in alert and maintenance behavior in various habitats (Hunt 1987). In marsh habitat, percentage of time in various activities: foraging 72.9%, alert 6.3%, maintenance 14.1%, resting 2.2%, and others 4.5%; in bay habitat, foraging 58.5%, alert 6.2%, maintenance 18.4%, resting 16.2%, and other 5.0%; in uplands, foraging 54.2%, alert 33.1%, maintenance 0.2%, resting 0.0%, and other 8.2% (Hunt 1987). Hunt noted that marsh and bay habitats are open and allow good predator detection and avoidance, in contrast to uplands where vegetation provides cover for predators (e.g., bobcats [Lynx rufus] and coyotes [Canis latrans]).
More than 500 h of diurnal time-budget activity data collected on Rocky Mtn. population birds during summer, migration, and winter: 99% of time spent in feeding, comfort movements, alert behavior, and locomotion (Drewien et al. unpubl. data). Adults spend more time in alert and comfort actions than yearlings and juveniles. Yearlings express more agonistic behavior and vocalize more than other social groupings but are intermediate in time feeding, alert, resting, and locomotion. Juveniles spend more time feeding and resting and less time vigilant than other groupings (Drewien et al. unpubl. data).
Attack may include Run-flap, Hiss, Gape, Bill-stab, Jump-rake (leaping while slashing with the talons), Wing-thrash, and occasionally Mob (>1 crane attacking the same target). These behaviors are directed at conspecifics during territorial encounters.
Alert behavior is evident when Whooping Crane notes some alarming stimulus; extends neck fully and head forward. Expands or contracts red crown and red-black mustache stripe; expansion indicates dominance or aggression, contraction subordinance or illness. Dance involves components of most agonistic displays, Attack, and other action patterns. Other displays described in Ellis et al. (unpubl. data).
Threat Displays. Strut is a slow walk with feet lifted high and toes extended, with the bird turned sideways to the object being threatened; feathers of thigh and tibio-tarsi may be flared and primaries lowered. Head is lowered until the bill touches the ground and the bird growls in the Bill-down-growl; thought to signify that the bird has a strong territorial commitment to the site. Crouch incorporates the incubation position; along with Preattack (spread and drooped wings with neck extended and head facing opponent), indicates imminent Attack.
Appeasement Displays. In Cower, subordinate bird holds body horizontal with neck curved down, feathers fluffed, and head held low and near the back. In Wing-flare-cower, spreads and droops wings. In Cower-crouch and Lie-crouch, bird lowers to Sit or Lie position; uses latter to hide from danger.
Male is the primary defender of family and territory. Nesting territories vary considerably in size: about 1.3–47.1 km2(Kuyt 1976a, b, 1981a, 1993). The “composite nesting area” is the area used by a pair of Whooping Cranes for a number of years. Resident pairs attack and chase singles and pairs trespassing into their territories. Males in the Rocky Mtn. population established and defended 16-ha or larger territories on the summering grounds beginning at age 3 yr, attacking Sandhill Cranes and conspecifics which entered the sites (Drewien et al. unpubl. data). These sites were generally occupied Apr to Aug or Sep. Females did not establish territories but used activity areas covering hundreds of hectares; sometimes moving 8 to >160 km in the same or the subsequent summer.
Winter Territoriality. Whooping Cranes occupy winter quarters for almost half the year. They tolerate close association with conspecifics at times on the wintering grounds, but pairs and family groups typically occupy and defend relatively discrete territories. Territory size is declining as population increases, averaging 117 ha in the 1980s (Stehn and Johnson 1987). Subadult and unpaired adults form small flocks and use areas outside occupied territories, near territories where they spent their first winter (Blankinship 1976, Bishop and Blankinship 1982). Newly paired cranes often locate their first territory near that of their parents (Bishop 1984, Stehn and Johnson 1987, T. Stehn pers. comm.). Whooping Cranes of the Rocky Mtn. population frequently flock with Sandhill Cranes and show no evidence of establishing winter territories, although such behavior might characterize family groups.
Dominance Hierarchies. Linear dominance hierarchy exists in captive and wild flocks (Kepler 1976).
Birds about 3 m apart in flying groups (Kuyt 1992) and roosting groups.
Mating System And Sex Ratio
Perennially monogamous; pair formation begins when birds are 2 and 3 yr old (Kuyt 1981a, Bishop and Blankinship 1982). Occasionally 3-yr-olds nest. Pair formation can be a lengthy process, developing over 1–3 winters from associations in subadult flocks on wintering grounds (Bishop 1984). Individuals will remate, sometimes within only a few weeks, following the death of their mate (Blankinship 1976, Stehn 1992b). Average age of first egg production is slightly > 4 yr (E. Kuyt pers. comm.). Males become sexually mature at a younger age than females. Sex ratios are approximately equal at hatching.
As a pair forms, the future mates associate continuously and perform several social and maintenance activities together, e.g., Unison Walk, Unison Call, and Dance. Dance may include most agonistic displays, elements of Attack, and other actions such as Spread-hold, Gape, Gape-sweep, Tuck-bob, Leap, Object-toss (a light object such as grass or feather is thrown up and attacked with the bill as it falls), Run-flap-glide, Hoover, and Bill Stab (Ellis et al. unpubl. data).
Allen (1952) described the Dancing behavior of a pair. See Figure 3 . “Suddenly one bird (the male?) began bowing his head and flapping his wings. At the same time he leaped stiffly into the air, an amazing bounce on stiffened legs that carried him nearly three feet off the ground. In the air he threw his head back so that the bill pointed skyward, neck arched over his back. Throughout this leap the great wings were constantly flapping, their long black flight feathers in striking contrast to the dazzling white of the rest of the plumage. The second bird (the female?) was facing the first individual when he reached the ground after completing the initial bounce. This second bird ran forward a few steps, pumping her head up and down and flapping her wings. Then both birds leaped into the air, wings flapping, necks doubled up over their backs, legs thrust downward stiffly. Again they leaped, bouncing as if on pogo sticks. On the ground they ran towards each other, bowing and spreading their huge wings. Then another leap! The climax was almost frantic, both birds leaping two and three times in succession. Quickly it was all over, after about four minutes, and an extended period of preening followed.”
Copulation; Pre- And Postcopulatory Displays
In Precopulation Display, either member of pair may walk slowly with bill skyward, neck extended and slightly forward, emitting a low growl in 0.5-s bursts at 2-s intervals; second bird begins walking in same manner behind first, bill-up, calling; female eventually spreads wings to side with secondaries drooped. In copulation, male walks and flaps onto back of female, lowers to sit position while flapping wings to maintain balance, presses his tail around his mate’s tail to complete cloacal contact (Ellis et al. unpubl. data). The Copulation Call increases until it becomes a scream. Copulation may occur at any time of day but is most frequent at daybreak. Pair bonds that have resulted in nesting appear to last until 1 member of the pair dies.
Social And Interspecific Behavior
Degree Of Sociality
Not as gregarious as Sandhill Crane; tends to associate as pairs or a family on summer and winter territories. At these periods, subadults may be solitary or in flocks of 2–7 birds. During migration, travels as singles, pairs, a family, or small flocks of 4–7 birds.
Some semblance of play, tossing of debris, is occasionally seen among juveniles.
Nonpredatory Interspecific Interactions
Associates in the nesting area include Sora (Porzana carolina), Red-winged Blackbird (Agelaius phoeniceus), Arctic Loon (Gavia arctica), and various ducks; sometimes tolerates or ignores other nearby birds and mammals (cattle, deer, etc.), but on other occasions pursues intruders.
Kinds Of Predators
Potential predators in the nesting area include black bear (Ursus americanus), wolverine (Gulo luscus), gray wolf (Canis lupus), red fox (Vulpes fulva), lynx (Lynx canadensis), Bald Eagle (Haliaeetus leucocephalus), and Northern Raven (Corvus corax). Nests destroyed by black bear and other mammals; prefledged chicks killed by wolves (Kuyt et al. 1981); overall impact of predation on recruitment remains uncertain. Coyote, red fox, and Northern Raven are known egg or chick predators in Rocky Mtn. population. Golden Eagle (Aquila chrysaetos) have taken young Whooping Cranes; also strike fledged chicks in flight; Bald Eagles have killed Sandhill Cranes; Whooping Crane responds to these eagles as predators. Bobcats have killed Whooping Cranes in Florida and Texas.
Chicks are particularly vulnerable until fledging (about 80 d); more vulnerable in dry summers when water levels are low and nesting areas are more accessible to predators. Parents remain alert for evidence of predators. Eagles are watched with Monocular-gaze (sideways viewing with 1 eye dominant). Alarm Calls may be given at sight of coyotes, bobcats, and other large predators. Adults may approach and threaten or attack small predators such as raccoons (Procyon lotor). They may give a distraction display toward a large predator such as a bear or wolf.