ATOLL RESEARCH BULLETIN

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ATOLL RESEARCH BULLETIN

No. 158

BIRDS SEEN AT SEA AND ON AN ISLAND IN THE CARGADOS CARAJOS SHOALS

by R. Pocklington, P.R. Willis and M. Palmieri

Issued by

THE SMITHSONIAN INSTITUTION Washington, D. C., U.

S .

A.

Uecwnber

3i, 1972

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BIRDS SEEN AT SEA AND ON AN ISLAND IN TIIE CARGADOS CARAJOS SIIOALS

by R. Pocklington, P.R. Willis a n d M. P a l m i e r i

During a second c r u i s e to the Indian Ocean by the Woods Hole Oceanographic Institution v e s s e l R.V. ATLANTIS I1 in 1965 a s p a r t of the International Indian Ocean Expedition, a r e t u r n v i s i t w a s made to the Cargados C a r a j o s Shoals, where we had previously gone a s h o r e i n November, 1963 (Pocklington, 1965). No other v e s s e l during the I.I.O.E. had a s i m i l a r oppor- tunity to o b s e r v e the western Indian Ocean at opposite s e a s o n s with the samc? personnel and techniques.

The Cargados C a r a j o s a r e interesting because they a r e geographicallji between the Seychelles, where s e a - b i r d s p e c i e s b r e e d m l i n l y in the northern s u m m e r (Loustau-Lalanne, 1963), and the Mascarenes, wheremany s e a - b i r d s b r e e d i n the southern s u m m e r (Newton, 1958).

The s p e c i e s l i s t whichfollows c o v e r s r e c o r d s n ~ a d e a t s e a between Trolnelin (15O52'S, 54O25'E), Ile du Sud in the Caragados C a r a j o s Shoals (16O49'S, 5S030'E), Rodriguez, and Mauritius, June 2-7, 1965, inclusive, and a s h o r e on Ile du Sud, June 3. N o m m c l a t u r e follows Alexander (19551, a n d names of c o l o r s a n 5 topozraphy of b i r d s follow Palrm?r (1932).

pztffin~n zheyfizinievi AudubonJs Shearwater

One at 1 8 ~ 5 2 ' 5 , 6 2 O 1 3 ' ~ , 4 June, in the vicinity of Rodrigoez. Bailey (1968) s a w few m o r e than 50 m i l e s f r o m t h e i r breeding grounds, and. Gill (1967a) found them common only in the vicinity of the Seychelles, Mauritius and Reunion, but not in the intervening s e a s , which hints at islands off Rodriguez as possible breeding stations, as suggested by Gill (1967b).

P t e v o d v o m Spp. Gad-fly P e t r e l s

On 4 June a t 1805Z1S, 62O13'E, nine p e t r e l s with grey upper-parts, white underparts and a d a r k leading edge to the upper wing, w e r e seen. They w e r e unlike any of the P e t r e l s and Shearwaters with which we were already acquainted. A possibility e x i s t s that t h e s e b i r d s were Barau's P e t r e l s I'tevodvoma havaui (Jouanin, 19631, of the existence of which we w e r e un- a w a r e a t the time. This b i r d b r e e d s on Reunion in the southern s u m m s r , dispersing l a t e

~ ~ r i l / e a r . l y May f o r p a r t s unknown (Jouanin and Gill, 19671. A recent examination of sub- f o s s i l p e t r e l bones f r o m Rodriguez (Bourne, 1968) indicates that gad-fly p e t r e l s did b r e e d there, although they apparently no longer do s o (Gill, 1967b).

Oceanites oceanicus Wilson's S t o r m - P e t r e l

Two s t o r m - p e t r e l s , dark with white rumps, Seen with the above-mentioned gad-fly p e t r e l s , were believed to be this species, ,which we r e c o r d e d with decreasing- frequency as we went south.

K. Pocklington: Marine Science Branch, Atlantic Oceanographic Laboratory, Bedford Institute, Dartmouth, Nova Scotia.

P.R. Willis: 10 Orne Square, Salem, Mass. 01970.

&I. P a l m i e r i : Woods Hole Oceanographic Institution, Waods Hole, Mass. 20543.

(Manuscript received J a n . 1971--Eds.)

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Two were seen between Cargados C a r a j o s and Rodriguez, one a t 1fJ025'S, 132~13'E, the o t h e r a t 1 9 ~ 0 9 3 , 6 2 ' 3 3 ' ~ . It h a s not been recorded in recent tim,?s f r o m Rodriguez (Bourne, 19681, nor f r o m 'Jargados C a r a j o s (Newton, 19581, though Staub and G d h o (1968) mention a r e d tail-feather picked up on Albatros I, Cargados Carajos. It breeds on the cliffs of Gunners Quoin, Mauritius (Newton, 1958) where many w e r e s e e n 7 June.

One adult flew about the ship while the party was a s h o r e on Ile du Sud. No others were s e e n until we approached Mauritius, 7 June, where they b r e e d (Gill e t al., 1970).

%la dactylatva Blue-faced Booby

T h r e e adults w e r e s e e n close to Ile du Sud, but they were not nesting t h e r e , though they do

011 Ile du Nord (Newiou, 1958; Staub and Gukho, 1968). T h r e e m o r e w e r e in a mixed flock with Sooty T e r n s , S t e m fuscata, between Rodriguez and Mauritius, where they b r e e d on Serpent I.

(Newton, 1958).

F w @ a nzinov Great Frigate-bird

In addition to numbers of unidsutifiable f r i g a t e s among l a r g e flocks of t e r n s feeding off Tromelin, where F. nzimv b r e e d s h u b , 1970) o t h e r s were seen betwren t h e r e and Cargados C a r a j o s 16O07'S, 56'05 E, feeding i n association with flocks of Soaty T e r n s . T h r e e all-black m a l e s w e r e positively identified among them. No m o r e were seen outside this a r e a .

Fvegata a r i e l L e s s e r Frigate-bird

Males of this species, identified by white patches on each side of the abdomen, were seen at s e a as we approached Ile du Sud. They w e r e soaring over groups of feeding Noddies Anow

spp. and Sooty Terns. No f r i g a t e s w e r e s e e n a t s e a subsequent to our visit to this island.

On Ile du Sud, there w e r e ca. 200 n e s t i n g p a i r s i n the N.E. and 60 in the S.W. of the island, a n i n c r e a s e over the total of ca. 200 p a i r s nesting in November 1963. The r e d gular s a c of s o m e sitting and flying m a l e s was inflated, in contrast to our previous visit, when none of the m : ~ l e s showed m o r e than a s m a l l shrunken throat-pouch. In the case of the Great Frigate-bird

011 Tower I. in the Galapagos, Nelson (1968) found that the pouch i s inflated f o r only three o r four weeks a t the beginning of the breeding season. If this holds t r u e f o r F. a r i e l then this indicates that the beginning of the breeding season was not long past. Staub, who v i s i e d during the l a t t e r half of April, 1968, found that "nearly a l l the m a l e s had their r e d gular pouch fully extended," and that eggs w e r e already p r e s e n t (Staub and Gu6h0, 1968).

Only one juvenile was seen flying over the island, which is in a c c o r d with the idea that they d i s p e r s e away f r o m the breeding stations while the adults remain relatively close by (Bailey, 1968). T h e r e were no hatched eggs, in contrast to November 1963, when eggs, naked young and downy chicks were sim~lltaneously present, a s shown in published photographs (Willis, 1966).

Reference to Table I shows that nesting o c c u r s in both northern and southern summbr, in con- t r a s t to F. n h o v which b r e e d s only in the s o u t h e r n spring. Also, the duration of the I.: a v i e l breeding cycle is no m o r e than 8-9 months, a s found by Gibson-Hill (Palmer, 1962), f o r F, andvewsi on C h r i s t m a s I., n e a r Java, and not 1 5 to 1 8 months, as found f o r F. minov on

Tower Island, Galapagos (Nelson, 1968), where long before the juveniles f r o m one season w e r e fully independent, the next season began.

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The f e m a l e L e s s e r Frigate-birds were of two types: bluish-gray bill, black eye-ring, breast p u r e white with a s h a r p demarkation betwaen the black of the throat and the white of the breast, side of neck and hindneck white; and, pink bill, r o s e eye-ring, white b r e a s t with cinnamon flecking which destroys the s h a r p demarkation of throat f r o m b r e a s t s o charac- teristic of the other type, side of neck as b r e a s t , the white of the hindneck obscured by black and cinnamon flecking. Both types w e r e sitting on nests.

These differences may be due to age o r stage of physiological cycle of one f o r m only, but the possibility exists that this r e p r e s e n t s a stable polymorphism o r a n overlap of breeding ranges of two previously undescribed f o r m s of this species. Staub confirmed this variation (Staub and ~ u k h o , 1968) and noted that "the eggs of the two v a r i e t i e s s e e m somewhat different in shape and size,'' a point that we had not noticed. He a l s o noted r e d eye-ringed females a s being m o r e numerous than the black-ringed variety.

Stevna dougalli Roseate T e r n

About 200 adults w e r e seen a s h o r e onthe sand-pit w e s t of Ile du Sud. T h e r e w e r e no young b i r d s a s t h e r e hadbeeninNovember 1963. Nesting would a p p e a r to be r e s t r i c t e d to the southern spring (see Table I) in contrast to the other western Indian Ocean breeding stations of this cosmopolitan species, where nesting is in the northern s u m m e r (Watson e t al., 1963). On islands a t comparable latitude off Western Australia, nestingin both April-June and November- December h a s been recorded (Serventy and Whittell, 1962).

Stevna fuscata Sooty T e r n

This species, by f a r the m o s t frequently encountered b i r d in the western Indian Ocean (pocklington, 1967) a s a l s o noted by P a r k e r (1970), was seen in hundreds a t s e a between Tromelin and Cargados Carajos, but was absent a s a nesting species f r o m Ile du Sud. A dozen o r s o w e r e seen flyipg over the island: they w e r e probably breeding on other islands of the group (Staub and Guebo, 1968). Between Cargados C a r a j o s and Rodriguez, and between there and Mauritius, where they breed (Gill e t al., 1970) s m a l l e r p a r t i e s of up to 30 were seen, but they w e r e a b s e n t f r o m the immediate vicinity of Rodriguez, a s a l s o noted by Gill (1967b) in September-October 1964, though they w e r e p r e s e n t in A p r i l (Bourne, 1968).

Amus stolidus Common Noddy

None w e r e seen a t s e a until we approached the Cargados Carajos reef where p a r t i e s were feeding in mixed flocks with Roseate and White T e r n s Gyfis alba. On Ile du Sud, a t l e a s t 200 individuals w e r e sitting on eggs and brooding downy young; older chicks and fledglings w e r e running about the island. T h e r e w e r e many dead and dying immatures; some w e r e heavily in- fested with ticks, o t h e r s by s e e d s adhering to the f e a t h e r s , making i t impossible f o r them to move. P a r k e r (1970) noted l a r g e numbers of dead and dying juvenile S t e m fuscata with A m m stolidus on Goelette Island, Farquhar, apparently starving and Bailey (1968) made a similar observation on Desnoeufs Island, Amirantes. O t h e r adult birds were gathered in groups of 50-60 a t the water's edge, where p a i r s w e r e observed in co.hla. Thus, a l l s t a g e s of the breeding cycle were in progress. F r o m the data of Table I it appears that breeding is well nigh continuous throughout the y e a r a t this latitude. A s i m i l a r situation apparently existed on Rodriguez according to ancient r e c o r d s (Bourne, 1968) and recently Common Noddies with young of a l l s i z e s were observed in mid-July on Sandy I. off R o d r i y e z [Bourne, 19681, though they were not breeding there in late September/early October (Gill, 1967b). A s we c r o s s e d the broad fringing reef of R o d r i y e z , Noddies Anous spp. w e r e the ouly birds seen. They r e - appeared off Mauritius where, on Serpent Island, they n e s t primarily in October and November (Vinson, 1950).

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A s in Nove:nh-r 1963, t h i s sps.>ies w a s nesting in low b u s h e s Tozivnefo?,tia sp. on Tle du Sud. I t apparently n e s t s continiously t h e r e (Table I). On Sandy I., off Rodriguez, t h e r e were n e s t s , but no ,?ggs i n Septemh?r/October (Gill, 196713). The nesting d a t e s on o t h e r Western Indian Ocean islands a r e : Seychelles, throughout the y e a r (Loustau-Lllanne, 1963); Chagos, D e c e m h e r / F e b r u a r y and, n n i n s e a s o n , May/August ( L m s t a u - L a l a n n e , 1982); Mauritius, throughout the y e a r with a peak i n September/Dacember (Newton, 1958). Off W e s t e r n A u s t r a l i a in the Abrolhos Is., hatching i s o v e r by niid-November, t h i s being the only breeding s e a s o n (Serveniy a n d Whittel, 1962). T h i s b i r d w a s not s e e n f a r out a t s e a . )

G),& a l h White T e r n

Only s e e n a t s e a as we approached Ile du Sud. T h e r e wzre about 500 p a i r s on the island, s o m e sitting on t h e i r s o l i t a r y egg on branches, on p i e c e s of c o r a l , on the ground and even in the y a n o - c o l l e c t o r s ' huts. O t h e r s w e r e brooding downy young o r feeding fledglings. It would a p p e a r that nesting in t h i s s p e c i e s i s continuous throughout the y e a r a t t h i s location (Table I) as i t i s in tile Seychelles (Loustau-Lalanne, 1963) and Rodriguez (Bourne, 1968, Gill, 196713).

ACKNOWLEDGEMENTS

The a u t h o r s wish t o thank Chief S c i e n t i s t A.R. M i l l e r , who included t h i s work i n a very f u l l ship's p r o g r a m ; Captain E. H. Hiller, officers and men of the Atlantis 11; R. G. M u m s , who accompanied u s a s photographer and t h e l a t e M. J e a n Vinson, f o r m e r l y D i r e c t o r of the M a u r i t i u s Institute. The field work was s p o n s o r e d by N.S.F. Grant GP281, and the p a p e r was written while the s e n i o r a u t h o r w a s in r e c e i p t of financial support f r o m the National R e s e a r c h Council of Canada a n d the National Science Foundation.

SUMMARY

A r e t u r n v i s i t w a s m l d e i n June 1965 to the C a r g a d o s C a r a j o s Shoals previously visited i n November 1963. T h e s e i s l a n d s a r e i n t e r e s t i n g as they l i e between the Seychelles, where much breeding is in the n o r t h e r n s u m m e r , a n d the M a s c a r e n e s , w h e r e many s p e c i e s b r e e d in the s o u t h e r n s u m m e r . R e c o r d s a r e a l s o given of a l l s p e c i e s s e e n at s e a between Tronielin, C a r g a d o s C a r a j o s , Rodriguez a n d Mauritius.

L e s s e r F r i g a t e - b i r d s , F v e e a l a u r i e l , w e r e nesting on the i s l a n d i n C a r g a d o s Carajos.

O u r v i s i t coincided with the beginning of the breeding s e a s o n . Other nesting b i r d s w e r e Comm3il Noddy A n o w s t o l i d u , ~ , L e s s e r Noddy A n m t e n u i v o s t ~ i s , White T e r n f o r which a continuous breeding cycle a t t h i s latitude i s i n f e r r e d .

B i r d s s e e n a t s e a include p e t r e l s , s t o r m p e t r e l s , tropic-birds, boobies, a n d t e r n s , a l l in s t n ~ l l n u m b e r s a t t h i s season.

REFERENCES

Alexander, W. B. 1955. B i r d s of t h e Ocean (2nd edition). London:Putnam.

Bailey, R. S. 1968. The pelagic distribution of s e a - b i r d s in the W. Indian Ocean. I b i s 110: 493-519.

Bourne, W.R.P. 1960. The p e t r e l s of the Indian Ocean. Sea Swallow 1 3 : 26-39.

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- - - - - ^-

1968. The b i r d s of Rodriguez, Indian Ocean. I b i s 110: 338-344.

G a r d i n e r , J. S. a n d C. F. Cooper. 1907. The P e r c y Sladen T r u s t Expedition t o the Indian Ocean i n 1905. Description of theExpedition: P a r t I I , M a u r i t i u s t o Seychelles. T r a n s . Linn. Soc., London 11, Zool., 12(2): 123-129.

Gill, F. 5. 1967a. Observations on t h e pelagic distribution of s e a - b i r d s i n the w e s t e r n Indian Ocean. P r o c . U.S.Nat. Mus. 23: 1-33.

- - ^{- -} ^- ^- ^- ^- ^-

⁹ B i r d s of Rodriguez Island (Indian Ocean). I b i s 109: 383-390.

ill, F. B., C. Jouanin andR.W. Storer. 1970. Notes on the s e a b i r d s of Round Island, Mauritius.

Auk 87: 514-521.

Jouanin, C. 1963. Un nouveau de l a ~ k u n i o i l "13ulwe1,ia Daifaui" Bull. Mus. Hist. Nat., 35: 593-597.

Jouanin, C. a n d F.B. Gill. 1967. R e c h e r c h e du &re1 d e Barau, I'telfodvoma balal.aui. Oiseau et. R.F. 0. 37: 1-19.

Loustau-Lalanne, P . 1962. The b i r d s of the Chagos Archipelago, Indian Ocean. I b i s 104: 67-73.

- - - - - - - - - -

1963. Sea a n d S h o r e b i r d s of the Seychelles. Seychel1es:Gov. P r i n t e r . Nelson, 5. 1968. Galapagos, Islands of Birds. London:Longmans.

Newton, R* 1958. Ornithological notes on M a u r i t i u s a n d the C a r g a d o s C a r a j o s Archipelago.

P r o c . Roy. Sac. A r t s Sci., M a u r i t i n s 2: 39-71.

P a l m e r , R. S. 1962. Handbook of North A m e r i c a n B i r d s . Vol. 1. Yale Univ. P r e s s .

P a r k e r , I. S. C. 1970. Some ornithological o b s e r v a t i o n s f r o m the w e s t e r n IndianOcean. Atoll R e s . Bull. No. 136: 211-220.

Pocklington, R. 1965. B i r d s s e e n on Coco Island, C a r g a d o s C a r a j o s Shoals, Ilidiaii Ocean.

Ibis 107: 387.

- - -

1967. O b s e r v a t i o n s by p e r s o n n e l of R.V. ATLANTIS 11 on i s l a n d s i n the Indian Ocean. Sea Swallow. 19: 38-41.

Serventy, D. L. arid H.M. Whittell. 1962. B i r d s of WestcrnAustralia. P e r t h , P a t e r s o n . Staub, F. 1970. Geography a n d ecology of Tromeliil Island, Atoll Res. Bull. 136: 197-209.

Staub, F. a n d J. ~ u 6 h o . 1968. The C a r g a d o s C a r a j o s Siioals o r St. Brandon: R e s o u r c e s , avifauna, and vegetation. P r o c . Roy. Soc, A r t s . Sci. M a u r i t i u s 3(1): 7-46.

Vinscm, J. 1950. L'Ple Ronde e t l ' n e aux Serpents. P r o c , Royal Soc. A r t s Sci., M a u r i t i u s 1: 32-52.

Watson, G.E., R. L. Zusi, and R.W. S t o r e r . 1963. P r e l i m i n a r y field guide to the b i r d s of the Indian Ocean. Smithsonian Institution, Washington, D. C.

Willis, P. 13.. 1966. Birdwatching at sea. Oceanus 12: 2-6.

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T a b l e I. R E C O R D S O F BIKDS B R E E D I N G O N CARGADOS C A R A J O S SHOALS

--- - --

P u f f i n u s p a c i f i c u s I n e s t s

--

S u l a d a c t y l a t r a b r e e d i n g a d u l t s b r e e d i n g breeding--

p a i r s

+---

^only p a i r s p a i r s

S u l a s a l a n e s t s a d u l t s

only

- -

F r e g a t a m i n o r n e s t s not a d u l t s b r e e d i n g n e s t s

n e s t i n g only p a i r s

F r e g a t a a r i e l

I

^young n e s t s & e g g s e g g s & young

s o m e e g g s only ? s u n g

I

S t e r n a d o u g a l l l younq not young e g q s &

b r e e d i n g only young

A n o u s t e n u i r o s t r i s

I

n e s t s e g g s & e g g s n e s t s n e s t s

young S t e r n a f u s c a t a

A n o u s s t o l i d u s

I

C y g i s a l b a e g g s & e g g s & e g g s e g g s e g g s

young ? young

young n o t e g g s a d u l t s a f e w

b r e e d i n g Y O U ~ S only young

--

e g g s & e g g s & e g g s & young e g q s e g g s

young 7 s o m e young young

Y e a r s

I

¹⁹⁵⁵¹⁹⁵⁶ ¹⁹⁶⁸ ¹⁹⁶⁵ ¹⁹⁰⁵ ¹⁹⁶³^{1 9 6 4}¹⁹⁶⁵ ¹⁹⁶⁵

M o ? t h s V i s i t o r s --

J a n . A p r . J u n e Aug

.

^Nou. ^{D e c .}

Newton S t a u b Poc1clin:ton G a r d i n e r S t a u b , S t a u b &

c t ill. & C o o p e r P o c k l i n g t o n GuGho

C t ai.-

-

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AFPZNDM

While t h i s :3a!)er wzs ;.n ,>reparation, i m p x t a n t accounts of s e a b i r d s

breed in^

on other oceanic islands in the t r o n i c s were published. These a r e by Bourne (1971) on the b i r d s of the Chagos Group (5O20'

-

1°35's, 71°20'

-

7Z040'E), S c h r e i b e r and As'lm,,le (1970) on C h r i s t m a s Island in the P a c i f i c Ocean (ZON, 157'Wj and H a r r i s (1969) on the Galapagos Islands (1°50'N

-

1°20'S, 89°-920W). We wish to review the r e m r d s of b i r d s breeding on C a r g a d s s C a r a j o s Shoals in the light of t h i s new information. T o avoid repetition, the n a m e s of the Islands will s s r v e to identify the authors; a l s o T r o m e l i n to indicate Staub (19701.

Pufiinws paczficus Wedge-tailed Shearwater

O c c u r s in the offshore w a t e r s of the Chagos Group during most of the y e a r a n d r e p o r t e d to b r e e d on s o m e outer islands f r o m Yovember to February. It therefore a p p e a r s to b r e e d in the s a m e s e a s o n (southern s u m m e r ) i n the Cagador C a r a j o s (Table 1) a s in the A m i r a n t e s ( P a r k e r , 1970), Chagos and Round Island off Mauritius (Gill z t a1.,1970). In contrast, on C h r i s t m a s Island in the equatorial Pacific, few a r e even p r e s e n t f r o m November to January.

The peak p e r i o d f o r eggs i s June to July a n d f o r chicks August to October, i.e. northern s u m m e r and fall.

Sula dactylatva Blue-face Booby

On C h r i s t m a s Island it l a y s a t a l l t i m a s of the y e a r but mainly f r o m April to October.

111 the Galapagos i t h a s an annual cycle, with colonies out of phase by up to f o u r msnths. I11 the Wastern Indian Ocean the November to January breeding on Cargados C a r a j o s c o m p a r e s with the October to November peak on Serpent Island (Vinson in Gill et al., 197C), the October peak on Latham :sland off the E a s t African Coast, 9 7 k m south of Zanzibar ( P a r k e r , 1970), alld the peak period of reproduction f r o m November to M a r c h on Tromelin, to indicate a similar out-of-phase annual cycle.

S u b s u b Red-footed Booby

T h i s b i r d h a s been reported to b r e e d in the Chagos Group in both July and Septemh2r. On C h r i s t m a s Island, somk? egg-laying o c c u r s in a l l m.mths. T h e r e a r e two peak p e r i o d s f r o m April to May and DecernSer to January. In the Galapagos (Tower Island only) i t i s suggested that the breeding cycle is l e s s than one y e a r to account f o r the different peak laying months in different y e a r s , though eggs have been found i n every month. On Tromelin nesting h a s been noted in August, Novemher and F e b r u a r y in different y e a r s s o the situation t h e r e might be comparabl&. The b i r d has now disappeared a s a breeding species f r o m Zargados C a r a j o s (Staub and Gueho, 1968).

Fvegata mino?, G r e a t Frigate-bird

On C h r i s t m a s Island m t x t laying is late M a r c h t o May, with chicks but no eggs September to January. The b i r d s a r e on individual c y c l e s because of the greater-than-annual cycle of successful b r e e d e r s . T h e r e i s m o r e p r e c i s e syuchrony within than between colonies. In the Galapagos t h e r e a r e annual breeding cycles on individual islands but breeding is not in phase on different islands. The available evidence f r o m Cargados C a r a j o s indicates laying f r o m November to J a n u a r y as compared with a l a t e August s t a r t on Tromalin, s o a situation s i m i l a r to that in the Galapagos may apply.

Fvegata a v i e l L e s s e r Frigatebird

On C h r l s t m l s Island t h i s b i r d l a y s f r o m late A p r i l to May. By January no eggs, chicks o r adults r e m l i n . One definite breeding season during the northern spring a n d s u m m e r is

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implied. In the Cargados C a r a j o s nesting w l s a l s o observed starting in late April (Staub and Guiho, 1968) a t the beginning of the cool d r y season. Eggs and young a r e a l s o p r e s e n t f r o m November to January a t the s t a r t of the warm wet season. On Tromelin, 480 km due west, the s p e c i e s was not breeding in late August, s o one long breeding p e r i o d s e e m s l e s s likely than two discontinuous ones a t this latitude.

Anous stolidus Common Noddy

In the Chagos t h e r e a r e apparently two main breeding seasons, May to August and Decem- b e r to F e b r u a r y but nesting f r o m September through November h a s a l s o been reported. On C h r i s t m l s Island eggs have been found throughout the y e a r but fewer f r o m July to November thau in other months. In the Galapagos, breeding is continuous but there a r e only a few eggs f r o m August to October.

Anous tenuivostvis L e s s e r Noddy

This bird nests in t r e e s in the Chagos in June and November through December. On C h r i s t m a s Island there i s one definite breeding season in the northern spring, layiug maiuly f r o m April to May. On Serpent Island both A . stolidus and A. tenuivostvis nest p r i m a r i l y in October and Novem'Jer (Vinson i n Gill et al., 1970). On the basis of these comparative data there m.ay be discontinuities in the breeding of these s p e c i e s on Cargados C a r a j o s during those m.mths, in particular F e b r u a r y to May, which corresponds to the uorthern fall non- breeding season a t C h r i s t m a s Island. T h i s statement supercedes our previous inference about the two noddies (see pp. 3, 4).

Gygis alba White o r F a i r y T e r n

In the Chagos Group i t h a s been found nesting in t r e e s in a l l islauds in February, May to July, September and October, and December. On C h r i s t m a s Island substantial numbers of eggs a r e laid in a l l months, the minimiim being around November. By analogy, continuous breeding a t Cargados C a r a j o s is therefore likely.

ADDITIONAL REFERENCES

Bourne, W.R.P. 1971. The b i r d s of the Chagos Group, Indian Ocean. Atoll Res. Bull.

149: 175-207.

H a r r i s , M.P. 1969. Breeding s e a s o n s of sea-birds i n the Galapagos Islands. J. Zool., Lond.

159: 145-165.

Schreiher, R.W. and N.P. Ashmole. 1970. Sea-bird breeding s e a s o n s on C h r i s t m a s Island, Facific Ocean. Ibis 112: 363-394.