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White Ibis
Eudocimus albus
Order
CICONIIFORMES
– Family
THRESKIORNITHIDAE
Authors: Kushlan, James A., and Keith L. Bildstein
Revisors: Heath, Julie A., and Peter Frederick

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Breeding

Figure 2. Annual cycle of the White Ibis

Phenology

In North America, onset of breeding readiness depends on photoperiod, as captive birds in Florida and S. Carolina begin to experience bare-part color changes in early spring (March). In coastal S. Carolina, massive courtship flights occur near colony sites following spring rains in March and April.

In Florida, nesting can be delayed for many months until feeding conditions become suitable, even until late summer or fall (Kushlan 1976a). In coastal S. Carolina, late nesting is often the result of late arrival of spring migrants from farther south. Owing to considerable variation in nesting synchrony, an entire nesting episode can last 8 wk to 6 mo (Williams 2007).

Nesting starts when conditions are suitable for highly effective foraging, primarily the availability of sufficiently shallow freshwater wetlands (Kushlan 1976a, Bildstein et al. 1990) ) to produce high prey availability (Gawlik 2002, Herring 2008). Actual timing differs substantially across range, even during seasonal drying period in Everglades. In coastal colonies in temperate zone, nesting occurs during or immediately following the “big rains” of the late winter and spring. In s. Florida, nesting in the interior ends with the onset of rainy season (Jun – Jul), whereas coastal colonies in the same area historically nested well into summer (Ogden 1994). Due to differing topography, such rains probably provide foraging sites in freshwater wetlands near coastal colony sites in S. Carolina (Bildstein et al. 1990) but interrupt drying patterns and prey availability in flat, continuous wetlands of s. Florida.

Nest building usually begins in spring to late summer, earlier (late Feb to Jun) in interior s. Florida than farther north, or along the Florida coast (Mar-Jun; Kushlan 1973b, 1977c, Frederick et al. 2001). In S. Carolina, nest building usually begins between early Mar and early Jun (Beckett 1965), usually within 10 d after the birds arrive from the south. In N. Carolina, in late Mar to early Apr (Allen-Grimes 1982, Shields and Parnell 1986). See Fig. 2.

Will renest following nest failures early in the breeding season, though the proportion doing this is unknown and may be small. Some ibises may initiate second attempts in different colony sites, as well as visit several colony sites before initiating their first attempt. Hence it is difficult to separate late first nesting attempts from early second attempts Williams 2007). Extremes for eggs in s. Florida, Feb–Sep; for S. Carolina, Apr–Jul (Bildstein et al. 1990). For coastal Georgia, as late as Jul (Teal 1965). In coastal S. Carolina, most eggs hatch in May and Jun; recently fledged individuals are first seen on nearby salt-marsh feeding sites in mid- to late Jun, flying to more distant freshwater wetlands one week later. In captivity with unlimited food, 3 – 4 nesting attempts and 3 broods possible over nearly 6-month breeding season in n. Florida (PCF unpubl.).

Physiology

White Ibises have cyclic gonad development that corresponds to reproductive activity; endocrine patterns are similar to other seasonal breeders with bi-parental care. Males and females have high testosterone concentrations during the display stage that decrease later during incubation and chick rearing (Heath et al. 2003). Testosterone concentrations are correlated with female bare part color change (Heath and Frederick 2006). Female estradiol is highest during display and chick rearing stages, male estradiol lowest during copulation. Female progesterone remains high during reproduction, male progesterone does not change.

Ibis body condition changes during reproductive activity, and between years (Herring 2008). Males may store energy before the egg-laying stage when they spend most of the time at the nest. Female condition improved from non-breeding to display stages, then decreased throughout the rest of the season (Heath et al. 2003).

Adult body condition appears to be critical for nesting. In captivity, mean gain of 107 g for males and females in the month prior to courtship; individuals capable of gaining this amount in < 14 d. During incubation, males lost an average of 43.2 g (4.6%; n = 14;) while females lost an average of 21.7 g (2.9%); n = 3). Females varied significantly in body condition throughout the nesting stages while male condition followed a similar trend but did not vary significantly. Highest body condition indices in both sexes were observed during courtship (Babbitt and Frederick 2008).

Nest Site

Selection Process

Colony sites usually develop from roost sites through the formation of daytime bachelor parties that form at the roost and on the ground nearby. Nests are near, but not necessarily on, the display site. Female sites the nest platform and builds the nest, which may be some distance from display site. Nest building is usually synchronous (onset within 4 d) within “neighborhoods” of 25 to 50 pairs in large colonies (Frederick 1987a). Although individuals maintain nest territories (see Behavior: territoriality), neighborhoods form as tight aggregations of nests with few nests added after the initial establishment of a neighborhood. Where White Ibises nest in colonies with other ciconiiforms, the presence of nesting individuals of earlier-nesting species may prompt ibises to nest at a colony site. In coastal NC, 94% of colonies were on islands created by dredge-spoil operations.

Site Characteristics

Nest in live and dead woody vegetation. Nests are typically in branch crotches, but also on multiple close branches and in herbaceous vegetation. In the latter, often supported on grass culms. As many as 47 nests in a single tree (Audubon 1844). In n. Florida in one colony (Rudegeair 1975b), 67% in Tamala littoralis, 12% in Quercus spp., 4% each in Sabina silicicola, Sabal palmetto, and Ilex vomitoria, 9% in vines; in another colony, 86% in Sambucus canadensis, 14% in Acer rubrum. In coastal Louisiana in one colony, 99% in live and 1% in dead Avicennia nitida (Hammatt 1981). In a colony in coastal N. Carolina, 38% in scattered red cedar (Juniperus silicicola), remainder in maritime thickets (Allen-Grimes 1982). In S. Carolina, nearly 100% of nests in one large colony on clumps of black needlerush (Juncus roemarianus, Bildstein 1993). In Everglades of Florida, nesting primarily in willow (Salix spp), cypress (Taxodium distichum), mangroves (Avicennia, Lanuncularia and Rhizophora) cattail (Typha spp.) sawgrass (Cladium jamaicense) and pond apple (Anona glabra).

In a survey of 232 colonies throughout the North American breeding range of this species (east coast US, Carolinas to Florida), 30% were in mangrove (Avicennia, Laguncularia, Rhizophora spp.; Hingtgen et al. 1985); also in Australian pine (Casuarina equisetifolia), Brazilian pepper (Schinus terebinthifolius), lantana (Lantana camara), button-wood (Conocarpus erectus), live oak (Quercus virginiana), laurel oak (Q. laurifolia), bay (Persea borbonia), red mulberry (Morus rubra), elder (Iva frutescens), willow (Salix spp.), wax myrtle (Myrica cerifera), swamp tupelo (Nyssa aquatica), common baldcypress (Taxodium distichum), cactus, grasses or sedges (Cladium jamaicense, Scirpus spp., Juncus roemerianus, Spartina cynosuroides), or on the ground (Audubon 1844, Bent 1926, Dusi and Dusi 1968, Kushlan 1973b, Rudegeair 1975b, Schreiber and Schreiber 1978, Girard and Taylor 1979, Frederick 1987c, Bildstein et al. 1990).

Grasses and sedges appear to be used when higher nest sites are not present or are being used by earlier-nesting species. Nest platforms often contain fresh leaves, replenished by the male during incubation. In n. Florida, averaged 3.65m ft (1.6, n = 999) aboveground; in coastal S. Carolina 2.95 m (0.09, n = 104) in mulberry (Post et al. 1985); 0.32 m (0.10, n = 64) in needle rush (Frederick 1987c). In coastal Louisiana, averaged 0.14 m (0.014, n = 170) above ground in black mangrove (Avicennia sp.; Hammatt 1981); in Florida 1.78 m in white mangrove (Laguncularia recemosa; Girard and Taylor 1979). At colonies where ibises nest later than other ciconiiforms, nests tend to be lower than those of other species, possibly because higher sites are less available.

Nest

Construction Process

Nest site selection falls to the female, who also has primary responsibility for building the nest. Sticks are brought by the male. In n. Florida, 38% of the sticks placed by female, 35% by female predominantly, 27% by male and female equally (Rudegeair 1975b). Males steal nesting material from existing nests, often in conjunction with attempted extra-pair copulations (Frederick 1987a), though females will also steal material from unoccupied nests. No evidence that ibises use the abandoned nests of earlier-nesting species in mixed-species colonies, but Glossy Ibises (Plegadis falcinellus) sometimes use abandoned White Ibis nests (Allen-Grimes 1982).

Female grabs nesting material crossways, shoves it into the nest platform, and moves it up and down, in a tremble shoving motion. Once twig is caught in nest material, can be further adjusted, removed, or replaced. Nest construction takes place throughout the day; usually takes less than seven days to build a nest.

Structure And Composition

Nest usually constructed of dead twigs, even in herbaceous colony sites; but low herbaceous nests often consist of matted and woven herbaceous vegetation from the immediate vicinity or from living clump of grass supporting nest, and some completed ground nests with eggs consist of fewer than 20, 10–20 cm pieces of cord grass (Spartina spp.). At a black mangrove colony site in coastal Louisiana, 65% of nesting material black mangrove, 35% Spartina alterniflora (Hammatt 1981). Twigs may be broken from nearby branches, found on ground under colony, pilfered from old or nearby nests, or gathered at some distance from the colony site. Sometimes lined with nearby grasses, moss, and cypress leaves (Wayne 1922, Stephens 1950). Discarded rope, paper, and plastic occur infrequently.

Dimensions

Nest measurements vary (Rudegeair 1975b, Frederick 1987c). Outside diameter: n. Florida, 254 mm (4.8, n = 1051); coastal S. Carolina, in shrubs (Iva frutescens) 287 mm (16.9, n = 10), in grass (Spartina cynosuroides and Juncus roemerianus) 253 mm (28.7, n = 20). Height: coastal S. Carolina, in shrubs 91.2 mm (11.6), in grass 57.2 mm (10.8, n = 20). Inside diameter and depth not recorded.

Microclimate

Some nests, especially those placed low in live woody vegetation, have 100% canopy cover; others in herbaceous vegetation have little, if any, canopy cover. Insulative value of nest not recorded.

Maintenance Or Reuse Of Nests; Alternate Nests

Nest maintained through hatching, and sometimes for several days thereafter, with additional sticks and lining added. In coastal N. Carolina, 12% of the nests were reused once, and 1% were reused twice. Young had fledged from 29% of these reused nests (Allen-Grimes 1982). In coastal S. Carolina, nests are rarely reused. Material may be pilfered for next nest. No alternate nests recorded.

Eggs

Shape

Varies from subelliptical to long subelliptical, sometimes quite elongated.

Size

Florida: length, 57.5 mm (± 3.2 SE; n = 20); diameter 38.7 mm (1.51; n = 20), Drum Island, SC (1957–1963): length, 58.2 mm (2.6, n = 79); diameter 38.7 mm (1.4, n = 79; W. Post unpubl. data). Dwarf eggs occur.

mass: coastal N. Carolina (fresh): 50.8 g (± 5.7, n = 30; Vleck et al. 1983). Each egg approximately 6% to 7% of female mass.

Eggshell Thickness

S. Carolina: pre-1947, 0.334 mm (n = 27); 1972–1973, 0.335 (n = 20; Blus and Lamont 1979).

Color

Splotched with brown over a base color ranging from cream to blue-green at hatching and fading to white thereafter. Surface texture: smooth and nonglossy (Baicich and Harrison 1997).

Egg Laying

Eggs normally laid every other day (Rudegeair 1975b, Shields 1985), with most clutches completed within a week. The first egg is laid five to six days after the beginning of copulations, and additional eggs are laid at one- to two-day intervals. Eggs are laid early in the morning.

Male is extremely aggressive and spends more time at the nest than does female during nest building and egg laying (Heath 2002). Male guards nest and female from other ibises, especially from nearby males collecting nest materials or seeking extra-pair copulations. Number of extra-pair copulations correlated with time female spends alone at nest (Frederick 1987a). Males guard nest during day, females guard at night. Unattended eggs destroyed by other ibises at the colony.

Nest is abandoned following predation, tidal inundation, aggressive interactions with neighboring ibises, human disturbance, or poor foraging conditions especially during rain-caused “reversals” of drying wetlands (Frederick and Collopy 1989a). No evidence for replacement of lost eggs or clutches. Intra-specific egg dumping suggested by some indirect evidence but not demonstrated.

Incubation

Onset Of Broodiness And Incubation In Relation To Laying

Eggs covered after laying, but continuous incubation begins with last egg.

Incubation Patch

Vascularized brood patches present on 90% of incubating males and females (Heath et al. 2003).

Incubation Period

On average 21 d, 22 d from first egg laid to hatching of first egg (Frederick unpublished). Details of variation unknown.

Parental Behavior

In S. Carolina, males incubated 55% (n = 11 pairs, 38%–68%) of the time during daylight observations (Frederick 1987b). Eggs and mate defended by male, who remains in residence throughout early nesting. Later, pair alternates nest attendance with the male feeding in early morning and evening, and attending the nest during most of the day (Kushlan 1976c, Frederick 1987a). Bill length is important in intraspecific dominance, and in an analysis of 16 members of ibis subfamily Threskionithinae, male bill length was highly correlated with colonial breeding behavior (Babbitt and Frederick 2007).

Time at nest low early in incubation (15.8 min/pair), increasing to high point at three weeks. Overall, inattentiveness about 31 to 33 min/d (Rudegeair 1975b). Time off eggs averaged 1.9 times and 1.9 min/hour on rainy days, and 4.3 times and 13.9 minutes per hour on sunny days. Incubating birds tend to flush more readily early in incubation than later, as well as during windy conditions (Shields and Parnell 1985). Some ibises attempt to incubate eggs while floating above them during tidal inundations of the nest (Frederick 1987c). When temperature is > 34°C, eggs are shaded rather than incubated. Other activities during incubation (times/h): preen, 2.6; twig pull, 1.9; feather ruffle, 0.20; head shake, 0.12; tail flick, 0.26; stretch, 0.24; scratch, 0.56 (Rudegeair 1975b).

Early in incubation changeovers include appeasement behavior and mutual head rubbing and bill popping. Later, no obvious displays.

Hardiness Of Eggs

No detailed information. Appear to be susceptible to heat and cold, as incubating birds sit tight in rain and shade during heat. Eggs left unguarded are generally destroyed or lost to nest-material piracy. Eggs covered with brackish water for more than one hour during tidal inundations early in incubation have hatched (Frederick 1987c). % Eggs hatched (as a proportion of eggs in nest at hatch date) in Everglades over 6 yr averaged 90.3% (range 85.4% - 97.2%, Semones 2003).

Hatching

Preliminary Events And Vocalizations

Young vocalize during pipping. Sequential eggs in clutch hatch one to two d apart.

Shell Breaking And Emergence

Young break hole in shell with egg tooth, eventually cutting a circle approximately one third of way from blunt end of shell. Hatchlings usually emerge 1-2 d after initial pipping.

Parental Assistance And Disposal Of Eggshells

No parental assistance recorded. Eggshells disposed of by adult, who picks up shell and tosses it away from nest with lateral shake of head.

Young Birds

Condition At Hatching

Bill straight and flesh-colored (#5, Smithe 1975 –81) with a dark neutral gray (Color 83) tip. Bare skin of face, legs and feet flesh color. Head and neck covered with dense, shiny jet black (#89) down, projecting caudally. Several white feathers form a spot on the crown of approximately 30% of nestlings. Remainder of body with sparse pale neutral gray (#86) down, except for shoulders and wings, which are covered with dark neutral gray (#83) down (De Santo et al. 1990).

Weak and uncoordinated; spend most of the time sleeping in a prone position. Eyes closed. Cannot stand or raise head at hatching; legs small and underdeveloped. On day 1 (age 1 d), begging consists of jerky lateral head movements.

In coastal S. Carolina, hatchling mass: 36.3 g (4.10, n = 72); bill (measured from tip to feather line), 17.6 mm (0.90, n = 72); tarsus, 16.1 mm (1.28, n = 72); middle toe, 18.0 (1.18, n = 72); wing chord, 22.5 (1.57, n = 72; De Santo et al. unpubl. data.).

Growth And Development

Rapid gain in biomass in first and third week after hatch, slower in second week during period of feather maturation (Kushlan 1977d). Growth of captive birds may be retarded. Growth rate may vary at a single colony site within and among years depending on the availability of appropriate prey. Mass increase modeled by logistic growth equation, K = 0.185, asymptote = 700 g, t (10–90) = 23 d.

Body parts grow at different rates, with legs, feet, and toes developing quickly, and bill much retarded (Kushlan 1977f).

Eyes begin to open at 1 to 3 d, and are completely open by day 9. Irises raw umber (color #223) through first month. By month 5 outer ring medium plumbeous (#87), inner portion Pratt’s Payne’s gray (88 details in De Santo et al. 1990).

Feather tracts visible at hatching. No visible feather growth until day 4 or 5 (4-5 d after hatching), when primaries begin to emerge; followed by feathers in humeral and alular tracts, as well as secondaries and tertiaries on days 6 to 10. Spinal and ventral tract feathers and rectrices emerge on days 8 to 12; crural and femoral feathers on days 24 to 32. Much of the down on crown replaced on days 32 to 46, but some remains for days after birds leave the colony site during weeks 7 and 8. Primaries completely unsheathed by days 45 to 60.

White egg tooth sloughed at 5 to 9 d. After 3 d, facial skin and orbital area darken to light neutral gray (#85). This color change proceeds distally until the proximal third of both mandibles is dark neutral gray. Remainder of bill becomes salmon color (#6). A band that darkens to dark neutral gray appears distal to the nares between 7 and 10 d. Bill begins to curve downward at day 14. Dark neutral gray areas of bill expand until most of the bill is dark by the beginning of week 5. During this time the pattern of the pied bill varies considerably among same-age nestlings (De Santo et al. 1990). At 6 wk bill light neutral gray, changing to pale pinkish buff (#121D) at the base and salmon color distally by week 9. Bare skin of face turns light neutral gray around day 2, and bluish gray by day 3. It is deep vinaceous (#4) by 5 wk, turning flesh color beginning in third month (De Santo et al. 1990). At 6 wk bill light neutral gray, changing to pale pinkish buff (#121D) at the base and salmon color distally by week 9. Bare skin of face turns light neutral gray around day 2, and bluish gray by day 3. It is deep vinaceous (#4) by 5 weeks, turning flesh color beginning in third month (De Santo et al. 1990). By 6 mo, bare skin is fleshcolor but paler than in adults. Juvenile legs and feet gray, turning to flesh color by third year.

Nestlings easily overheated during the ten days. Seek shade in vegetation thereafter. Chilling as a result of tidal inundation of nests containing young < 10 d old was the principal cause of nestling mortality at a coastal colony site in S. Carolina (Frederick 1987c).

Incapable of holding head up for first day or so. Hatchlings lie on side with head back or down, brooded by parent. By day 3 chicks beg with loud trills while holding their head up and extending their wings; shuffle to edge of nest to defecate. Legs, feet, and toes become large and strong quickly. By day 6 chicks crawl on their tarso-metatarsi. Free-living chicks beg continually unless being brooded. During week 2 chicks flap one or both wings while begging, and by the end of week 2 are capable of leaving the nest to flee approaching humans. Trilling vocalizations, which vary among individuals, become longer and louder throughout the first four weeks (De Santo et al. 1990). By week 3 can climb out of nest onto limbs or ground, but cannot climb back into nest in tree if they fall out; can swim if they fall in water. Also by week 3 they pirate food from each other, and in colonies with nests near the ground, crèche in groups of at least 30 similar-aged juveniles, ranging at least 20 m from their nest. By week 4 chicks spend most of their time perched on vegetation away from their nests or wading and probing in shallow water.

Siblicide not reported. Chicks are pirated of their food by other chicks as well as by marauding adults. During times of food shortage, larger male nestlings may survive better than females (Adams and Frederick 2008b).

Flight develops gradually. At two weeks chicks begin to spend much time flapping wings. Can fly short distances in colony by fourth or fifth week. Sustained flights of > 50 m occur by week 6. Juveniles begin to leave island colony sites, crossing water boundaries of ≥ 750 m to feed with adults and other juveniles at end of week 7 (De Santo et al. 1990).

Parental Care

Brooding

Adults continue brooding and shading young immediately from hatching to day 10. Young can move from their nest by week 2, at which time both adults forage at the same time, and young are brooded usually only at night. By week 3 brooding has ceased. Male broods early in the day, female later in the day and at night. In Florida most feedings early and late in day. Young have corresponding endogenous rhythm (Kushlan 1976c). Feeding rhythms can differ elsewhere, at different stages of the nesting cycle, and with different food supplies.

Feeding

Fed beginning second day. Both parents feed young. In coastal S. Carolina, males responsible for 57% of regurgitations (n = 11 nests, 38%–72%) to small nestlings (Frederick 1987b). Adults feed young directly. Adult grasps chick’s bill, stimulating it to raise its head, and then regurgitates into its mouth. After a week, young initiate feeding with a begging display by poking at and touching base of parent’s bill, while flapping one or both wings. Nestling head placed within bill of adult. Series of head jerks and bobs results in regurgitation by adult directly into the bill of the young. Infrequently, food regurgitated onto the nest floor, where it may be picked up by young. Transfer takes 3-10 s.

After two weeks young often drape one wing over the back or neck of the feeding adult and pull adults head downwards. Adult may delay feeding or delay return to the nest, or may place bill out of reach of nestlings. When young are capable of short flights, parents sometimes induce flying by alighting close to young and then taking off with the young in pursuit. Other young and even adults pirate food directly from feeding adult, as well as from recently fed young (Rudegeair 1975b, Frederick 1985).

No indication food of adults and young differs, but no studies. Food much macerated during early chick phase, apparently by muscular stomach, less so as young grow. Only slightly, if at all, diluted with water; no indication that water alone is brought to young. Adults in coastal colonies feed freshwater prey, especially crayfish, when available, rather than locally abundant fiddler crabs, which are also taken by adults (Bildstein et al. 1990). Food type varies with local availability of prey, and may switch from crustaceans to fish (Dorn et al. 2008). Young fed as frequently as nine times per day. Younger chicks fed more frequently than older chicks. Amount of food brought per trip not recorded, but load sometimes fills entire gullet from gizzard to mouth.

Largest chick fed first after commencement of active begging. Adult may attempt to feed all young, but considerable competition. Larger young often climb atop smaller young in gaining access to food (Rudegeair 1975b). Adults sometimes terminate feeding by standing erect, or later by flying away. Young may follow adults by flying in latest stages of feeding.

Nest Sanitation

Young move to edge of nest to defecate over the side by day 3, usually upon being fed. No fecal sacs. No invertebrate associates in the nest are recorded. Parental carrying of young not recorded.

Cooperative Breeding

Nonbreeding second-year birds, which typically comprise < 1% of all individuals at a colony, often interact with nestlings. These second-year helpers often move among nests, interacting with several broods per hour, preening and shading nestlings. Nestlings beg from helpers but food transfers not reported. Helpers tend nestlings only when adults are absent, withdrawing from nest when adults return, sometimes chased from the site by returning adults. Results of helping with respect to the parents or young unknown; may provide useful experience for non-breeding second-year birds. Helping occurred regularly at a coastal colony in S. Carolina, but because second-year birds are so few at this colony, few nestlings interact with helpers.

Brood Parasitism

Interspecific brood parasitism not reported. In coastal S. Carolina, intraspecific parasitism, or egg dumping, estimated responsible for 2.7% of eggs laid. Dumping occurs at least during host’s egg-laying sequence, and possibly before and after. Effect on host and host’s response to egg dumping unknown.

Fledgling Stage

Behavior

Young spend considerable time perched in vegetation at this time, and they engage in short flights, especially when parents return with food. Crèches of up to several hundred similar-aged young form at this time.

Departure From Nest

Young leave mainland colonies as early as 40 d after hatching, one to two weeks later at island sites requiring flights over water. Young marked with radio transmitters left an island colony in coastal S. Carolina at 47 to 56 d of age (n = 8; De Santo et al. 1990), and radio tagged chicks in Florida Everglades left at 51 – 70 d of age (mean = 61d, n = 122 radio-tagged young, Semones 2003). Some chicks follow after adults, begging as they leave the colony; others depart alone or with several young. Departures occur throughout the day. Aborted attempts at departure occur frequently, with chicks flying from < 20–100 m over water at island colonies before returning to the site. Some young return to roost at colony after initial departure. No indication that adults feed young away from the site.

Growth

Leave colony at 79% of adult mass; middle toe at 100% of adult size at 29 d; tarsus at 98% adult size upon departure from colony, adult size at 52 d; central rectrices at 92%, adult size at 55 d; 8th primary at 93%, adult size at 74 d; bill at 68%, adult size at 112 d (Kushlan 1977f).

Association With Parents And Other Young

Do not associate with parents outside of colony site. Form juvenile flocks for at least several months, possibly longer (Bildstein 1983, Petit and Bildstein 1986). Long-term stability of these flocks unknown.

Ability To Get Around, Feed, And Care For Self

Young typically probe for food at the colony site and make sustained flights of 50 m or more for at least one week prior to departure. Feeding on the ground, they sometimes consume large quantities of mud. Feeding behavior similar to that of adults, but handling times longer and intake rates approximately 40% adult rate for at least several weeks after leaving colony site (Henderson 1981, Bildstein 1983). Often choose inappropriate habitat. Require several weeks to fly in flight lines typical of the species (Petit and Bildstein 1986).

Immature Stage

At least a portion of the immature population accompanies adult breeders at colony sites, where they roost together and often interact with nestlings (see Cooperative breeding). Second-year immature birds, which often flock together, feed at approximately 70% the rate of adult breeders (Bildstein 1984).