Bijdragen tot de Dierkunde, 55 (2): 219-232 — 1985

Observations on the behaviour of the Scarlet Ibis,

Eudocimus ruber, in Artis Zoo, Amsterdam

by

H. Albrecht R.E. Spil M.W. van Walstijn &

Royal Zoological Society "Natura Artis Magistra",

Plantage Kerklaan 38, 1018 CZ Amsterdam, The Netherlands

&

Department of Animal Behaviour, University of Amsterdam, The Netherlands

Abstract without overt signs of aggression. The hierarchy was not

linear but could be subdivided into three groupings. The The Scarlet Ibis, Eudocimus ruber (Linnaeus), fam. of bird correlated with status a was sex-dependent, weight Threskiornithidae, is the closest relative ofthe White Ibis, and of but length the bill, not with nest-ownership or age. Eudocimus albus (Linnaeus). The two species live in adjoin- The breeding behaviour of the Scarlet Ibis and the is known about the ing geographical areas. Nothing White Ibis seems to be so similar that, bearing in mind Scarlet Ibis’s in the wild and little breeding biology only the be their similarity in morphology, question may posed about its breeding biology in captivity. A better under- whether they are conspecific. standing of the breeding of this species in captivity should

its and also elucidate its help to improve management to Zusammenfassung relationship with its much better known counterpart, the

White Ibis. Der Rote Sichler, Eudocimus ruber (Linnaeus), Fam. Three of behaviour in types display are recognized Threskiornithidae, ist der vikariierende nächste Verwand-

the the and courtship: snap display, dipping snap display te des Weißen Sichlers, Eudocimus albus (Linnaeus). Von also in The latter occurs greeting ceremonies, twig pulling. der Brutbiologie des Roten Sichlers ist aus Freiland und

together with the up-down display, and as a precopulatory Ein besseres Gefangenschaft nur wenig bekannt.

stable for activity. Breeding pairs are one breeding cycle, Verständnis dieser empfindlichen Art soil dazu beitragen,

but occasionally promiscuous matings can be observed. Of sie besser zu schützen und die Beziehungen zum Weißen

16 birds in 1982, 12 bred in all with a breeding again 1983, Sichler zu klären.

different partner. Bei der Balz können drei Verhaltensweisen

is of Egg laying preceded by a period increasing ap- unterschieden werden: Schnabelschnappen, Beugeschnap-

of both members of the the pearance couple on und Letzteres ist auch beim together pen Zweigschütteln. Begrüßen where copulation takes place. Nests contain 2-3 nest, eggs, und, zusammen mit dem Ab-auf, beim Paarungsvorspiel

which are incubated for 21-23 is indicated beobachten. Während eines sind Männchen days. Hatching zu Brutzyklus

failure a sudden decrease in incubation. Hatching can by und Weibchen fest verpaart, gelegentlich konnten Fremd-

be succeeded the of clutches. by laying replacement beobachtet werden. Von 16 die in paarungen Vögeln,

Nesting failures were due to destruction of nests or wählten alle in 1983 young, 1982 verpaart waren, Brutvögel (12

often resulting from disturbances humans or domestic by Vögel) einen neuenPartner.

cats. One incubated for 4 months without pair over ap- Vor dem Eierlegen sind die Brutpartner regelmäßig zu-

interruption, without being parent probably eggs present sammen am Nest, wo auch die Paarungen stattfinden. Ein

for of the time. most Gelege (2-3 Eier) wird 21-23 Tage bebrütet. Nach dem than males. Nest Females spend more time incubating Schlüpfen werden die Jungen zunächst gehudert. Streu-

reliefs much 1 than in occur at a higher rate (ca. per hour) nende Katzen oder auch menschliche Störungen können

the wild 2 For to 3 weeks after (ca. per day). up hatching, den Brutprozeß leicht stören. Mißlingt ein Gelege, wird

the almost one parent bird stays at nest continuously. oft sogleich mit einem folgenden begonnen. Ein Paar brü- visited other Unattended nests are quickly by birds, über 4 Monate ohne vermutlich tete Unterbrechung, sogar males. One the predominantly parent, mostly male, ohne Eier.

almost chases intruder varia- immediately an away. Slight Weibchen brüten mehr als Männchen. Brutablösungen

tions in behaviour could not be correlated with in viel öfter 1 breeding treten Gefangenschaft auf (ca. pro Stunde)

breeding success. als im Freiland Bis 3 Wochen nach (ca. 2 pro Tag). etwa

A dominance hierarchy could be distinguished between dem Schlüpfen ist ein Elternteil beinahe konstant am Nest.

adult birds. Aggressive encounters consisted of three dif- Unbewachte Nester werden schnell durch fremde Vögel behaviour threat ferent patterns: fighting, forward and (meist Männchen) besucht. Diese werden sogleich verjagt, stab-and-counter stab. Often bird another meist Männchen. Aus dem Verhalten eines festen one gave way to vom

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1. Distribution of the Scarlet Ibis in South America of Ch. Its northwestern Fig. (courtesy Luthin). counterpart, the

White this the Ibis, overlaps range only near border of Colombia and Venezuela (Luthin, pers. comm.).

Brutpaares ließen sich keine Rückschlüße ziehen, ob sein geographical distribution is restricted to

Bruterfolg gut oder schlecht sein würde. and inundated in the mangrove swamps plains Adulte Vögel lassen eine Rangordnung erkennen. Bei northern part of South America (fig. 1). The agonistischen Begegnungen lassen sich drei Verhaltens- birds live in often mixed with weisen unterscheiden: Kämpfen, Drohen und Schnabel- large colonies, of the Ciconiiformes fechten. Oft gibt ein Vogel seine Über- oder Unterlegen- other members order heit durch oder Ausweichen erkennen. nur Verdrängen zu (herons, spoonbills). The number of Scarlet Die Hierarchie ist nicht strikt lineär. Drei Ranggruppen Ibises is decreasing rapidly, as the birds are konnten unterschieden werden, innerhalb deren sich auch very sensitive to human disturbance and Dreiecksverhältnisse oder andere komplizierte Beziehun- limited in their choice of habitat erkennen ließen. Der eines (ffrench & gen Rang Vogels hängtab von

In French Geschlecht, Gewicht und Schnabellänge, jedoch nicht von Haverschmidt, 1970; Spaans, 1982).

Alter oder Nestbesitz. Guiana, intensive hunting takes place for the Das Brutverhalten des Roten und Weißen Sichlers zeigt feathers which are then used in imitation so viele Übereinstimmungen, daß die Frage berechtigt ist, flowers (Betlem & De Jong, 1983). ob wir es mit zwei Arten oder nur mit einer Art zu tun ha- Little behavioural research has been ben. done on

the Scarlet Ibis. Some behaviour in the field has

been described by ffrench & Haverschmidt

INTRODUCTION (1970); Risdon (1969) and De Tarzo Zuquim

Antas (1979) mention some breeding records in

The The Scarlet Ibis, Eudocimus ruber (Linnaeus, zoos. White Ibis, Eudocimus albus (Lin-

is of the coloured has been the of extensive 1766), one most strikingly naeus, 1766), subject members of the family Threskiornithidae. Its ecological and ethological research by Kushlan

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Fig. 2. The old aviary in Artis Zoo, built in 1863-1866 (cf. Anon., 1867). Reproduced from an engraving after a drawing

1868 in “Geillustreerde medaille Natura Artis Amsterdam”. A by W. Hekking Jr., published ca. van Magistra te nearly identical lithograph, drawn by the same artist, has been published in the yearbook of the Royal Zoological Society

“Natura Artis for the 1869. the round in the middle is the summer residence of the Magistra” year Nowadays, cage

Scarlet Ibises.

(1973, 1976, 1977 and 1978) and Rudegeair records from some other zoos have also been

(1975). taken into account.

Cross breeding between Scarlet and White

Ibises has occurred in Florida, where the

Scarlet Ibis in 1961 THE COLONY IN ARTIS ZOO was introduced (Zahl, 1967) and in the northern part of South America where the distribution of Scarlet and The Scarlet Ibis has been in Artis Zoo range kept

Ibis White overlaps slightly (Ramo & Busto, since 1916 in separate summer and winter

The residence is of 1982; Luthin, pers. comm.). quarters. summer a cage ap-

6 7 back The present study has been carried out in the proximately 4J4 x x m (fig. 2). The of

Artis Zoo under the auspices of the University the cage is a brick wall covered with ivy. Seven of Amsterdam and the Royal Zoological Society prefabricated nests are placed in the ivy at

"Natura Artis Magistra", Amsterdam. Obser- heights varying from 2.5-5 m (fig. 3). More

concentrated loose material added the vations were on breeding nesting is on ground.

and social interactions. several behaviour Breeding The cage contains branches, some

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3. Ibises with artificial sometimes build 30-40 Artis A. F. Nord- Fig. nest platforms, which they up cm high (photo: Zoo,

heim).

bushes and a small pond. From our observation last 6 years has varied from 2-9 young (mean

The birds be point it was not possible to look into the nests. 4.7). can recognized individually

In 1983 the consisted of 27 birds. coloured both May group by rings worn on legs.

The ibises varied in from 1 20 age to years.

died Three birds during the breeding season,

of probably as a result disturbance caused by METHODS OF OBSERVATION domestic cats. Two birds suffered from a broken bill from some earlier mishap. They, On April 26th, 1983, the birds were transferred and did in the winter observa- 12 others, not participate from their quarters, where no breeding process. Fledging success during the tions could be made, to the summer aviary.

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1983 made From 28 April up to 31 August we

30 minutes observations, spread throughout the day, totalling 134.5 hours. Initial observations

of had been made in the summer 1982.

all birds of behaviour For on nests three types

recorded: were standing, incubating or reliev-

ing partner. Incubating birds were identified by

the of the recording ringing combination part-

elsewhere in the Each ner off duty aviary. brood

scored for duration and of relief was variety

behaviour.

Besides also followed activities at the nest, we agonistic encounters, foraging and resting.

Apart from these quantitative observations,

of behaviour qualitative descriptions were made

such and patterns as courtship, copulation greeting. Fig. 4. The relation between time of the day and the where For data we used, ap- analysis number of birds feeding or resting. propriate, the Mann-Whitney U test (MWU), the the 2 2 and the sign test, x test (x ) Spearman prey items such as insects, amphibians and Rank Correlation Coefficient (SRCC) at a molluscs are taken out of shallow water or ex- significance level of 0.05 (cf. Siegel, 1956). mud. In the this posed zoo behaviour is shown

in the absence of these stimuli even (in vacuo).

The foraging rhythm in nature shows a

RESULTS similar cycle. Early in the morning and before

nightfall the ibises forage in flocks (ffrench &

Daily activity Haverschmidt, 1970).

Periods of increased activity were observed Sexual dimorphism when before 7 a.m. and after 5 p.m., a great

the deal of the birds were foraging on ground. Scarlet Ibis show the same sexual dimorphism

behaviour Resting predominates between these as described for the White Ibis by Kushlan

2 peaks (fig. 4). (1977). Males of the White Ibis are heavier and

of have bills than For the Foraging consists of 2 different types longer females. Scarlet behaviour: of food 2 Ibis inferred this correlation from eating supplied (at p.m., we copula-

small and when the ibises tions. From this evidence mainly fish) probing, circumstantial we sex- walk slowly and frequently make short pecks in- ed another five birds; three birds could not be

In small sexed this table to the ground (Kushlan, 1978). nature, way (cf. I).

TABLE I

Sexual in and bill size S.E. = standard dimorphism weight (grams) (mm). error.

Adult male Adult female

X S.E. N X S.E. N ± Range ± Range

Bill size 132 ± 1.3 104-144 9 109 ± 0.7 98-119 6

Weight 959 ±53.5 890-1060 9 786 ±55.3 695-840 7

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Pair formation

The pair bond is established by mid-April when

still in the birds are their winter quarters (Van

Not much Ommeren, pers. comm.). courtship behaviour was observed after the birds had

entered the summer residence. Five of the seven

the nests were occupied by established pairs on

the day of release. One couple split up later and

another female. male was seen courting

Three behaviour different types of display

can be distinguished in courtship:

for 1. The snap display (after Rudegeair, 1975,

its head in the White Ibis). The male moves

downward a forward, slightly direction by

stretching its neck, simultaneously making a

snapping motion with the bill. The bird

moves up and down, wings slightly spread.

2. The dipping snap display (Head Bobbing in

Rudegeair, 1975) closely resembles the snap

display, except that the snap is directed

straight downward. Instead of extending the

the male makes motion with neck, a dipping

the neck and the head. (We chose this term

because the term head bobbing does not in-

dicate the resemblance Fig. 5. Ibis preening the underpart of its wing (photo: with the snap Artis Zoo, A. F. Nordheim). also display. Besides, Rudegeair uses the

another of i.e. term for type behaviour, for

of the and the begging young.) quency intensity longer two partners

3. Twig pulling. The male closes the mandibles stay together.

over a twig and moves the head to and fro,

and down. The with which or up intensity Copulation

the behaviour is shown varies. Twig pulling All copulations and copulation attempts also occurs in other situations such as (Af=43) took place on a nest. Precopulatory greeting and copulation, performed by both behaviour consists of twig pulling, with male male and female. and female standing close to each other. The The displays are frequently interrupted by male sometimes crosses his neck over the neck preening (fig. 5), feather ruffling and inactivity of the female. When the female slightly lowers and they are, seemingly, not directed against a her body, mounting takes place. Postcopulatory particular individual. The displays disappear behaviour consists of preening or standing. soon after a female is tolerated on the nest and Copulations took place in the week prior to becomes a partner. incubation. In this period the couple spends the When one bird approaches partner at the much time together on the nest. nest, the latter starts greeting. This is an up- down display with twig pulling. Often the arriv- Collecting of nest material ing bird also shows twig pulling. When twig

the their Both pulling jointly, partners often cross male and female are seen carrying twigs necks. The greeting display decreases in fre- and leaves to the prefabricated nest-platform.

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2 in field = Nest material can be scarce the near to a unsuccessful couples (x 2.04). Hatching suc-

correlated with the of breeding colony and ibises have been seen steal- cess was not age a ing material from other nests (Rudegeair, breeding bird.

In where of In birds leave for the 1975). our group, a surplus nest nature, foraging

offered the this when As material was on ground, pirate grounds they are not incubating. a

of the distance the brood behaviour was also seen, being performed more result long to nest,

females. in by males than by One nest reliefs take place 2-3 times a day only (ffrench & particular, when littleattended by the breeding Haverschmidt, 1970; Rudegeair, 1975) and

of this behaviour. In the Amsterdam couple, was a target pirate always within 30 seconds.

relief fre- captive flock, we found a much higher

between 0.75 and 1.25 quency, varying per Incubation hour. Observations in "Het Noorder Dieren-

and in In nature the Scarlet Ibis usually lays two eggs park" at Emmen (The Netherlands)

indicate that (ffrench & Haverschmidt, 1970). Under optimal "Vogelpark Walsrode" (F.R.G.) conditions, with good food availability, three this frequency is not uncommon in captive

take be laid. Four seldom found. birds. Brood reliefs did not as eggs can eggs are place

Incubation for the situation in Eggs are laid at intervals of 2 days. smoothly as Rudegeair states for Scarlet Ibises lasts for 21-22 the wild. variable in and captive days They were very length

difference (Risdon, 1969). In the wild an incubation could last up to 5 minutes. No was

found between and period of 23 days was found (ffrench & successful unsuccessful

and birds in = and Haverschmidt, 1970). Based on these data, relieffrequency (MWU, p 0.285)

behavioural in in- relief duration = Relief fre- on changes our group, we (MWU, p 0.107). ferred that the incubation time about the and duration were not cor- was quency strongly

related = same r (21-23 days, fig. 6). (SRCC, s +0.41).

often the bird did im- During cold days the birds were seen Often incubating not rise

with in dorsal incubating their bills hidden the mediately after its partner had arrived. The lat-

the feathers. When temperatures were high, ter then showed different types of behaviour. birds the The bird in- were seen standing over eggs (or began by walking around its

with feathers and then showed hatchlings), wings spread, erect cubating partner twig pulling and the behaviour If still gular pouch vibrating. This near the partner's head (fig. 7). no reac- was only observed when the nest was fully ex- tion was forthcoming, the bird approached its

the When closer and its back. posed to sun. they are disturbed partner even put one leg on under such this behaviour is not This made the bird stand circumstances, always incubating up

minutes. shown and an embryo can die within and leave, or the birds would circle around each

This probably contributed to the low hatching other (fig. 8) after which either of the partners

No success. The behaviour resembles sunbathing left. correlation was found between quick behaviour (Wennrich, 1982) which is shown off relievers and breeding success. the nest.

in Both sexes take part incubation, with females spending more time on it in the morn- The young

= and males in the after- ing (MWU, p 0.001)

noon = The overall three (MWU, p 0.032). presence Although nests containing young are not

for both on the did not differ uncommon in the all three seldom nest significantly wild, young

= in sexes (MWU, p 0.12). However, successful survive (ffrench & Haverschmidt, 1970). The

the females be for couples spent significantly more major reason seems to competition space.

time the = In Artis Zoo on nest (MWU, p 0.029). there were seven breeding couples.

No difference in time in- Three raised significant spent couples one young, one couple cubating could be found between successful and raised two.

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Fig. 6. Nest activities of two pairs in the breeding season 1983. Pair I changed nest site in June. The male of pair II

the of his in A = of least B = the changed partner June. presence at one nestowner at nest; presence two nestowners

incubation the o = one x = together at the nest; C = by nestowners; expulsion by nestowner; copulation or copulation

= chick heard chick found attempt; □ or seen; † = dead; ↑ = chick left nest.

The hatchlings were invisible until they were legs remaining black. The bill turns black, ex-

which remains old enough to raise their heads (2-3 days old). cept for a small band at the base,

in down. is white. They are covered black The bill

with black feathers pink-white a tip, measures approx- After 10 days, the first contour ap-

2 and is this time the imately cm not yet curved. The ventral pear. By nestling starts exploring

the the part of the body turns greyish after 1 week, surrounding branches, using claws, wings

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7. The male left is induce his leave the Artis A. F. Fig. on the trying to partner to nest (photo: Zoo, Nordheim).

and bill for but the climbing, always returns to and flapping the wings. With increasing age,

From this onwards it is left alone the is aimed towards the nest. age more bobbing parent's bill, and and still later its The more by the parents. at distal part. squeaking

bird When a visiting lands on the nest, the turns into screaming and the wings are flapped

sometimes for but later when of the lands nestling begs food, on violently. Often, one parents crouches and silent. When confronted the it its head from keeps on nest turns away the chick with which increases the begging, a visitor reacts aggressively, begging even more.

the pecking nestling on the head. Crouched Both male and female take part in caring for

left unharmed. of the the time in- young are Screaming offspring. Couples spend more

alarms both and the the young one or parents the male cubating eggs than brooding hatchlings,

chases = immediately the intruder away. The during their first week (MWU, p 0.029). In

unmated male after visitor is usually an bird, or the first three weeks hatching the female

in the time the male female. Yearlings also show great interest spent more on nest than the nestlings. One of the visitors was often seen (MWU, p = 0.029). However, females do not

the chicks of This is the preening one nest. only brood more than males (MWU, p = 0.057).

in the Ibis that relief case of allopreening Scarlet we There is no difference in frequency before observed. In the White Ibis it seems be of and after of the to hatching young (MWU, more regular occurrence (Rudegeair, 1975). p- 0.1).

After weeks the able 4-5 young fledge, being

distances. to fly short None of the young was Visiting behaviour the after this. Until well seen returning to nest after the fed the Often bird observed fledging, young are by parents. a was visiting a nest

takes = Feeding place by regurgitation (fig. 9) (N 49) which had already been occupied by a

but deserted for few which is elicited of the was a minutes. This by begging young. Beg- pair,

done males females with ging consists of bobbing the head, squeaking visiting was by or or

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their claim stake and the nest could be con-

sidered abandoned.

Dominance relationships and agonistic behaviour

In the breeding season a colony of captive

Scarlet Ibis shows territorial a pronounced ag-

which result in and gression can damaged eggs

even destroyed nests (De Tarzo Zuquim Antas,

This is 1979). comparable to the White Ibis in

the field (Rudegeair, 1975). Outside the colony

the at foraging grounds no aggression is ob-

served. Nestlings of the Hermit Ibis, Geronticus

eremita (Linnaeus, 1758), like the White Ibis

compete aggressively for food. A linear

dominance hierarchy develops with the oldest

chick on top (Thaler et al., 1981; Oliver et al.,

1979; Rudegeair, 1975). Young of White Ibis

which have left the colony form flocks in which

stable for a hierarchy develops several days

when is in access to provided food given a

natural environment. This hierarchy appeared

also to be positively correlated with size

(Rudegeair, 1975).

From our observations of adult birds, we

Fig. 8. The male crosses his neck over his partner. The into divided the agonistic behaviour two com- female will leave and sit down not again on the nest viz. ponents, aggressive behaviour on the (photo: Artis Zoo, A. F. Nordheim). nestsite and behaviour in the aggressive open

of the enclosure. space

behaviour Aggressive on the nestsite consists

without of of visitors a nest of their own. A nestowner always expulsion by nestowners. The most

chased such intruder done form of is The an away. This was common aggression fighting.

2 the significantly more frequently by males (x test; nestowner quickly returns to nest after a

it. p<0.05). visitor has landed on He spreads his wings

In 35 and the neck total we observed visits from males and frequently pecks at of the intruder.

visits from females. 11 Nestowners visited 24 Many birds have an almost bare neck at the end

times and non-nestowners 25 times. No signifi- of the breeding season. A visitor is always

differences exist between driven the if cant males and away by nestowner, the visitor had

in this the females performing behaviour, nor be- not already left before nestowner arrived.

and Female Three of tween nestowners non-nestowners. different forms aggression were

nestowners showed this behaviour in the of the visiting more distinguished open space

than enclosure. With frequently females without a nest (MWU, increasing intensity this was p = 0.05). the forward threat, stab-and-counterstab, and

When showed In the forward a pair a decreasing presence fighting (Rudegeair, 1975).

4 with on the nest, either about weeks after hatching, threat, the body was held horizontally the

or when brood had birds neck extended and the bill directed forward attempts failed, many

visited the nest. After 2 or 3 days, the original against the opponent. In stab-and-counterstab,

alternative with the nestowners made no particular attempts to pecks are exchanged oppo-

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9. A bird food from his Artis A. F. Fig. young picks regurgitated parent (photo: Zoo, Nordheim).

birds from other 2 Birds nent, with feathers on neck and back erected groups (x test, p < 0.01).

In the from A birds from their and the wings slightly spread. fighting group displace own bills touch other in the from B each as nestsite en- group significantly less than birds group

All three of could C 2 counters. types encounter or group (x test, /?<0.01, jb<0.02, respec-

it Birds from B birds from have a winner or end undecided. Frequently tively). group displace also occurred that two birds confronted each group A significantly less than birds from their

of with 2 other with no overt signs aggression but own group (x test, /><0.01). They displace

birds from C than one bird fleeing. group significantly more

birds 2 From all aggressive confrontations in the from their own group (x test, p<0.01).

of the enclosure = 135 in 1982 open space (N

in in bird for and 334 1983) which one gave way

dominance order. another we constructed a TABLE II The birds could be divided into three groups of the dominance in Composition groups

The status of a bird is (table II). expressed by 1982 and 1983 (see also fig. 11). and/or lost. the number of confrontations won Group 1982 1983 Group A contains those birds which

drove other birds times A 3 crcr 3 significantly away more crcr

than driven themselves. they were away Group B 9 crcr 7 crcr

without B contains those birds a significant dif- 4 9 9 4 9 9

3 ?? ?? ference in driven 4 driving away or being away.

C 4 4 Group C contains those birds which significant- 9 9 9 9 2 ?? 2 ?? ly have been driven away more than having Total 25 driven other birds 24 away (sign test, p< 0.05,

N There difference = 27, x= is a 7). significant The ?? indicate that during the season between the B and C in the sex of birds was not known. groups A, driving away these

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than significantly more dominant females

The dominant A (MWU, p <0.05). most group

contained only males. The birds from group C,

for which the sex could not be established, ap-

peared to be females, according to weight and

bill size measurements. Males chase others

significantly more often than females did

order (MWU, jfr<0.05). The dominance was

neither correlated with having a nest (SRCC,

r = + nor with r = + s 0.21), age (SRCC, s 0.06),

nor with visiting behaviour (SRCC,

r = of s +0.17). Changes group membership

within one season occurred between A and B

and between B and C (fig. 11).

DISCUSSION

Comparison with the natural situation

Fig. 10. Dominance based on expulsions between the Because of lack of data on the Scarlet Ibis in the members of three The size groups. of the square represents data with field data field, we compared our on the amount of expulsions caused by each bird from that the White Ibis The the of 1975; Kushlan, group. arrows represent percentage expulsions (Rudegeair,

directed each member of the indicated The che- This to group. 1973, 1976, 1977, 1978). seems justified quered, bianco and striped markings expulsions represent because of their close taxonomic relationship. toward members of their members of sub- own group, to a The of daily activity our captive group closely missive and members of dominant group to a group, matches White Ibis in the activity curve of the respectively.

Finally, birds from group C displace birds from

the than other two groups significantly less

birds from their 2 in own group (x test, jb<0.05

both A bird from A cases). group displaces

other birds significantly more often than a bird

from 2 group B (x test, p< 0.001) or from group

C 2 from B (x test, p< 0.001). A bird group

birds from other displaces groups significantly

often than bird from C does 2 more a group (x

test, /?<0.001). (Fig. 10.)

A dominance linear hierarchy, as described

for White did Rever- young Ibis, not emerge.

sals, triangles or other circular relationships obscured such clear relationships. Only female- female confrontations were unidirectional.

The dominanceorder in the three groups ap-

It peared to be sex-dependent. was positively Fig. 11. Changes in dominance orders between 1982 and

with = and correlated weight r 1983. The numerals indicate the number of birds. Be- (SRCC, s +0.5) bill size r = Males were tween 1982 and 1983 two birds died and onebird (SRCC, s +0.65). grew up.

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field. In fixed than do females. The males the spite of food being provided at more frequently are

The hours outside their activity period, the birds not selective as to males or females. most

is dominant males show In forage early in the morning when no food most of the aggression. available. Kushlan demonstrated male accounted for of the total (1976) an en- 1983, one 20% dogenous rhythm for food intake in nestlings number of dislodgements of other birds. No

correlation found between and correlated this with the foraging rhythm of significant was

Both Kushlan's and data dominance and behaviour and between the adults. our sug- visiting

dominance and gest an endogenous foraging rhythm. nestownership.

The of bird Normally two brood reliefs per day are found status a can change over two

that the As based in the field. Rudegeair (1975) states seasons. our method of ranking was

do number of reliefs reflect the distance from the on observations of a whole season, we not nest to the foraging grounds. He found frequen- know if these changes have been brought about cies of one per day for remote nesting colonies gradually.

three for colonies. The dominance in the Scarlet Ibis to per day adjacent nesting hierarchy bill Males In our captive situation, where the distance be- was correlated with size and weight.

bills heavier than females. tween nest and food is minimal, a higher fre- have longer and are

of It be that the bill has quency is to be expected. A frequency one may supposed longer a

hour less be detrimental to social to Kushlan per or even seems to function, as, according the at the nest. Whereas reliefs in the field in the sexual White peace (1977), equally dimorphic

in difference with has always occur within 30 seconds, reliefs our Ibis, no regard to feeding

often took several the been found. Further with group minutes, leaving investigations regard

relief and to the of this sexual are eggs exposed. However, frequency significance dimorphism duration correlated with were not hatching suc- necessary. cess in our small sample. More data and com-

with the field situation desirable. parison are Division of labour between sexes From breeding behaviour alone it was not

of possible to predict the success a breeding cou- Both males and females were seen taking twigs

seemed the mentions that the ple. Breeding success to depend rather to nest. Rudegeair (1975)

incidental influences. male White Ibis collects the material and heavily on nest

In the White Ibis, the male chooses the nest the female builds the nest, sometimes helped by site. This might explain the more frequent the male. Since we observed this carrying of

behaviour shown the visiting by males. Visiting by twigs throughout season, we assume that

be this is of maintenance activities which nestowners can partly explained by the rob- part nest

behaviour is of nest if this are mediated the of bing material, pirate partly by "offering a pres-

of Scarlet Ibis behaviour in the integral part ent". Archibald et al. (1980) claim that this field. Nest material after sexual stimulation of is, all, supplied freely behaviour functions as a in our situation and is scarce in the field. the partner. Since we observed this behaviour

the number of visits until well after the However, greatest nest copulation period we suggest

behaviour that it functions the cannot be contributed to pirate to set partner at ease. because visits no were Thaler al. this function during many attempts et (1981) assign same to

the made to take nest material. Possession of a nest corresponding behaviour in the Hermit

be factor in the life of the where it is shown males. may an important Ibis, only by

Scarlet Ibis. This is also illustrated by the fact According to Kushlan (1976) females of the that for several couples were "breeding" White Ibis incubate mainly at night and males several months end. the on during day. Rudegeair (1975) observed that

The establishment of dominance the alternate the other a hierarchy sexes on nest every day. in the Scarlet Ibis appears to be sex-dependent. Our observations demonstrate that females

Males drive number of birds in the away a greater spend more time incubating morning

Downloaded from Brill.com10/08/2021 02:07:07AM via free access 232 R. E. SPIL ET AL. - BEHAVIOUR OF SCARLET IBIS

than in the afternoon. In how far this is deter- FFRENCH, R. P. & F. HAVERSCHMIDT, 1970. The Scarlet

Ibis in Surinam and Trinidad. Living Bird, 9: do mined by captivity conditions we not know. 147-165.

KUSHLAN, J. A., 1973. Promiscuous mating behavior in and White Ibis Comparison of the Scarlet the White Ibis. Wilson Bull., 85 (3): 331-332.

1976. in the White Ibis. , Feeding rhythm nestling Luthin (pers. comm.) has studied various Wilson Bull., 88 (4): 656-658. and of ecological morphological aspects 1977. Sexual in the White Ibis. Wilson , dimorphism

Eudocimus ruber and E. albus. He concludes that Bull., 89 (1): 92-98.

1978. Feeding of birds. Res. they are virtually the same in all respects. Com- , ecology wading Rep

natn. Audubon Soc., 7: 249-297. data and paring our on courtship copulation OLIVER, W. L. R., M. M. MALLET, D. R. SINGLETON & literature with the on the White Ibis, we can S. Observations the J. ELLET, 1979. on reproductive

support his conclusion. It appears that no behaviour of a captive colony of Bare-faced Ibis barriers exist behavioural to prevent hybridiza- Geronticus eremita. Dodo, J. Jersey Wildl. Preserv.

the colour difference Trust, 16: 11-35, pis. 1-8. tion, though might pre-

C. B. 1982. Son Eudocimus ruber RAMO, & BUSTO, y vent complete interbreeding. The possibility of E. albus distintas especies? Donana, Acta Vertebrata, physiological barriers has not yet been in- 9, 404-408. observed vestigated. As we the Scarlet Ibis only RISDON, D. H. S., 1969. The breeding of Scarlet Ibis in further behavioural studies in the captivity, (Eudocimus ruber). Avicult. Mag., 75: 165-167.

T. 1975. The behavior and field are desirable. RUDEGEAIR, J., reproductive

ecology of the White Ibis (Eudocimus albus): 1-147 (Ph. D. Thesis, Univ. Florida). ACKNOWLEDGEMENTS SIEGEL, S., 1956. Nonparametric statistics for the

behavioral sciences (international student We would like to thank Dr. B. Heuts for his help with edition): i-xvii, 1-312 (McGraw-Hill Kogakusha, Tokyo etc.). statistics, and Dr. B. M. Lensink, Drs. D. Dekker, J. SPAANS, A. L., 1982. De Rode Ibis: een pronkjuweel van Jansen and K. Schoelitz for making these observations de Zuid-Amerika. overstromingsvlaktes van tropisch possible. Het Vogeljaar, 30: 189-193.

TARZO ANTAS, P. 1979. the Scarlet REFERENCES ZUQUIM DE, Breeding

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ANONYMOUS, 1867. De nieuwe volieres. Jaarboekjevan het ZooYb., 19: 135-139.

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nithinae: their future in the wild and in captivity. Int. species of ibises (Threskiornithidae) at the Walsrode

Zoo. Yb., 20: 6-17. bird park, Germany. Avicult. Mag., 88 (2): 96-100.

BETLEM, J. & B. H. J. DE JONG, 1983. De rode ibis moord ZAHL, P. A., 1967. New scarlet bird in Florida skies

in Frans Guiana. Het 21 Natn. 132: 874-882. Vogeljaar, (4): 192-198. geogr. Mag.,

First draft received: 30 March 1984

Final draft received: 25 June 1985

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