ATOLL RESEflliCH BULLETIN Notes on the Wedge-tailed Shearwater at J-Ieron Island, Great Barrier Reef, Australia A. 0 . Gross, J. M. Moulton, and C. E. Huntington Issued by THE 'PACIFIC SCIENCS BOARD National Academy of Sciences--National Research Council Washington, D. C. November 1-5, 1963 Notes on the Wedgetailed Shearwater a t Heron Island, Great Ear r ie r Reef, Australia A . 0. ~ r o s s l , J . M. Moultonly2, and C. E. ~ u n t i n ~ t o n l ~ ~ Introduction During th r ee weeks of the southern summer, December 10, 1960 t o January 1, 1961, two of us ( ~ r o s s and ~ o u l t o n ) had an opportunity t o study the behavior and ear ly nesting a c t i v i t i e s of the Wedge-tailed Shearwater Puffinus pacif icus -- chlororhynchus Lesson, loca l ly known a s the Mutton Bird, on Heron Island in the Capricorn Group a t the southern end of the Great Barr ier Reef, F a c i l i t i e s of the Heron Island Research S ta t ion of the Great Barr ier Reef Committee a r e g ra te fu l ly acknowledged. Moulton was conducting a research program on Heron Island a t the Marine Research Stat ion during October and November, 1960, during which he observed the annual a r r i v a l of the birds, t h e i r mating and nesting, and recorded t h e i r c a l l s . Thus t he period of observation extended through three months of the b i rd ' s breeding season of 1960-1961, and i n December Gross and Moulton worked together. The topography and vege- t a t i o n of Heron Is land have been described by Fosberg, Thorne, and Moulton (1961). The Wedge-tailed Shearwater i s one of t he most common and wide- spread shearwaters of the t r o p i c a l and semi-tropical par t s of the Pacific. I t s breeding range extends from the Revil la Gigedo Islands off Baja California t o the Seychelles and lviascarene Islands off Mada- gascar and from the Pescadores Islands i n Formosa S t r a i t s t o Henderson Island i n the southeastern Tuamotus. I t s southernmost breeding s ta t ions a r e off the southeast coast of Australia and i t s northernmost in the Leeward Hawaiian and Bonin Archipelagoes. I t s d i s t r ibu t ion and system- a t i c s have been discussed by Murphy (1951) who recognized two subspecies, Puffinus pacif icus pacificus of t he Kermadecs, F i j i s , and Norfolk Island, and P. 2. chlororhynchus, occupying the r e s t of the range. Oliver (1955) believes t h a t these birds do not migrate, but remain in the seas adjacent t o the breeding is lands outside the nesting season; t h e i r great powers of Department of Biology, Bowdoin College, Brunswick, Maine. Observations were made during tenure of a Fulbright Scholarship a t the University of Queensland, Department of Zoology, and of a John Simon Guggenheim Memorial Foundation Fellowship. Support was a l so provided by National Science Foundation Grant G-44.03 and the Woods Hole Oceanographic Ins t i tu t ion . Supported by NSF Research Grant G5575 and NSF Undergraduate Research Par t ic ipat ion Grant G11869. f l i g h t a l l ow them t o range widely, however, a s ind ica t ed by Murphy's r e p ~ r t of specimens t aken hundreds of mi les from any poss ib l e breeding s t a t i o n . The Wedge-tailed Shearwater i s known by s e v e r a l common names i n d i f f e r e n t a r e a s of i t s d i s t r i b u t i o n , such as Wedge-tailed Puf f in , Wedge- t a i l e d P e t r e l , Mourning Bi rd , Moaning Bi rd , o r Ghost E i r d because of i t s c a l l , Black Burrowers and t h e u s u a l name, Mutton Bi rd , The l a t t e r name i s a p p l i e d t o s e v e r a l o t h e r spec i e s such as P. t e n u i r o s t r i s , g. g r i s e u s , P. carne ipes , and P. b u l l e r i . The name Mutt& Bird a rose from t h e - t a s t e of t h e flesh: Desc r ip t ion The plumage of t h e Wedge-tailed Shearwater shows two co lo r phases. The dark phase has t h e upper s u r f a c e of t h e plumage a sooty brown, t h e pr imar ies and t a i l a r e black, t h e ch in , t h r o a t , and forehead brownish gray, and t h e remainder of t h e under su r f ace a dusky brown. I n t h e l i g h t phase t h e b i r d s a r e brown above, but t h e under p a r t s a r e whi te with gray a long t h e borders between t h e two co lo r s . The under t a i l cove r t s a r e black i n both forms, The b i l l i s s l a t e o r l e a d co lor , t h e i r is dark brown,.the t a r s u s , f o o t , and n a i l s f l e s h co lo r , and t h e o u t e r edge of t h e o u t e r t o e s da rk ly pigmented. The o u t e r t o e s a r e s t ronger , thickened, and ca l loused , probably due t o t h e g r e a t e r use o f t hese t o e s i n digging. Only t h e dark forms a r e found on Heron Is land . The Wedge-tailed Shearwater i s polymorphic, t h e l i g h t and dark phases occu r r ing toge the r i n some colonies , while a t h i r d in te rmedia te form i s sometimes fotmd (Murphy, 1951). Although t h e propor t ion of l i g h t phase b i r d s i s h ighe r in t h e nor thern p a r t of t h e range, t h e s e c o l o r phases do no t c o n s t i t u t e geographica l subspecies , as was formerly maintained (Loomis, 1923), Geographical v a r i a t i o n , both i n s i z e and i n c o l o r phase propor t ions , occurs wi th in t h e subspecies -- Puf f inus - p a c i f i c u s chlororhynchus. A number of a l b i n i s t i c and semi -a lb in i s t i c forms of t h e Wedge-tailed Shearwater have a l s o been repor ted (lrlunro, 1944). Measurements in mi l l ime te r s and weights in grams o f f i v e specimens of Wedge-tailed Shearwzters from Heron I s l a n d a r e given in Table I. The measurements and weights a r e of l i v i n g b i r d s , sexes n o t determined. The n o s t r i l - b i l l measurements were from t h e a n t e r i o r edge of t h e n o s t r i l opening t o t h e t i p of t h e b i l l , The eye-bill measurement was t h e d is - t ance from t h e a n t e r i o r edge of t h e eye t o t h e t i p of t h e b i l l . h he o t h e r measurements a r e s tandard, ) Table I Measurements in millimeters and weights in grams of f i ve adult Heron Island Wedge-tailed Shearwaters Length Extent Wing Tarsus Foot ~ i l l ( c u l m e n ) Nostr i l -bi l l Eye-bill Weight Mean 437 l O I & 294 49 54 33 3 2 53 404 Some measurements of 5 birds, 2 males and 3 females, from the Tonga Islands were made by Davidson (1931) on January 6, 1921: Wing T a i l Culmen Tarsus Average 2 males 289.0 135.5 41 25 46 Average 3 females 289.0 135.0 39.0 39-0 Arr ival a t Heron Island No Wedge-tailed Shearwaters were observed on Heron Island when Pioulton arr ived on the is land f o r the f i r s t time on October 4, 1960, He captured and. photographed one of the f i r s t a r r i v a l s of 1960 near the Marine Stat ion on October 8, 1960, and the f i r s t c a l l notes of the year were heard l a t e r t h a t night. By October 11 large numbers had arr ived and were present from then on u n t i l our departure. Many of the shear- waters fed a t sea during the day, of ten with Noddy Terns, Anous sp. None of them were seen on the i s land during the day, except in burrows, but thousands of them poured onto the i s land a t dusk and departed the next morning. By November inany f resh burrows had been excavated in the sand and apparently old ones were renovated and lengthened. The Nest Burrow The openings of the tunnels leading t o the nest ing cavity a r e usually wider than high and la rge enough t o admit t he birds with room t o spare, Five representative openings were 10 x 15, 9 x 15, 13 x 13, 1 0 x 18, and 20 x 25 centimeters i n size. The length of tunnel var ies with repeated use, the character of t he s o i l , and obstructions encount- ered i n digging. In some cases i n which the tunnel was l e s s than half a meter long we could see the egg o r the incubating bird; a few tunnels were a s long a s 3 meters. The majority of the nes t s could be ea s i l y reached by inser t ing the arm and required no excavation t o obtain the adul t bird o r i t s egg. The nes t s had only a scant l i n ing of grasses and twigs and it was not unusual t o f ind the egg on the sandy bottom of the nesting bowl without any nesting material. The excavated tunnels s t a r t ed down usually a t a s l i g h t angle and then paral le led the surface of the ground. The burrows of former years were renovated and were dug much longer than the f reshly dug tunnels. Several of the birds were seen digging t h e i r nesting holes a t t he s t a r t , i n which the legs and f e e t play an important role. The bird would r e s t on i t s s ide and by extremely rapid s t rokes of the l eg would make the sand spray upwards f o r a s much a s a meter. Presently the b i rd would turn t o i t s o ther side and continue digging with the opposite foot . The t a r s i of the Wedge-tailed Shearwater a r e long and strong and well adapted t o digging. The beak, contrary t o what one might expect, was not used t o any great extent i n digging. The burrows on Heron Island were very close together, sometimes 3 o r 4 t o the square meter, so t ha t the ground was almost completely undermined. In walking across a nesting area, one was constantly breaking through in to the burrows even i n places where the surface of the ground seemed t o be firm and sol id . IYIany of the nesting burrows on Heron Island were under and among tne tangled roo ts of Pisonia and other t rees . I n a section of the nesting area near the guest houses of the ho te l the birds tunneled under the buildings and other s t ructures . A l a rge water tank res t ing on the ground was so completely undermined with tunnels made by the birds t h a t it sank deeply on one side and had t o be rese t . The custom is t o 12y chicken wire (wire ne t t ing) around buildings t o prevent burrowS ng underneath. The cabin which the senior author occupied bias i n the midst of a heavily populated section of the shearwater colony. An area of 20 x 25 meters had been cleared of vegetation and leveled d i r ec t l y i n f ront of our cabin. Approximately 50 p i r s of birds continued t o use the area i n s p i t e of the rad ica l changes made by man's intrusion. Banding of birds elsewhere has revealed tha t other shearwaters and pe t r e l s pe r s i s t i n occupying the t r ad i t i ona l grounds, even returning t o the same burrow i f it remains i n t ac t from one nesting season t o the next. The Egg The onset of egg-laying occurred with surprising uniformity. Although more than twenty burrows i n d i f f e r en t sections of the island were examined almost d a i l y , t he f i r s t eggs were not found u n t i l 15 December. On t h a t d a t e we suddenly found eggs commonly, t h e major- i t y of n e s t s examined contained an egg where before t h e r e had been none, and s e v e r a l eggs were found f r e s h l y l a i d on t h e su r f ace of t h e ground. The occurrence of a l a rge number of eggs on t h e open ground i s d i f f i c u l t t o expla in , b u t i t i s poss ib l e depos i t i on on t h e ground occurred when a burrow had not y e t been excavated o r when a burrow had been f i l l e d in . A nes t ing a r e a near t h e h o t e l bu i ld ings was ve ry much dug up by the b i r d s . The a rea was smoothed over by a t r a c t o r sc raper , f i l l - i ng up a l l of t h e nes t ing tunnels . It was a t t h e beginning of t h e egg-laying season, and a s a r e s u l t t h e b i r d s seemed bewildered when they appeared i n t he evening. Many eggs were depos i ted on t h e ground dur ing the n igh t , but such eggs were never incubated, a l though ac- cording t o :lowell and Bartholomew (1961) on Midway I s l and lithe Wedge-tailed Shearwater commonly n e s t i n shal low depress ions of t h e sand. The n e s t is usua l ly i n a t l e a s t p a r t i a l shade, bu t i n r a r e i n s t ances n e s t s were placed completely i n t he open.': I n 1910 on Raoul I s l and of t h e Kermadec group many eggs of t h e IJedge-tailed Shearwater were l a i d on the su r f ace of t h e ground; i n t h e previous year a s torm f i l l e d many of t he burrows wi th sand and rocks, which s e t s o hard the bFrds could not burrow (Ol iver , 1955). The s i n g l e egg of t he Vedge-tailed Shearwater i s e longate , ovate i n shape and pure white i n c o l o r w i th a matte sur face . Ten eggs measured by us v a r i e d i n length from 60.3 t o 68.2 mm. (mean 62.7), i n width from 40.7 t o 43.0 mm. (mean 41.8), and i n weight from 53.7 t o 64.1 grams (mean 59.0). These means a r e c l o s e t o those g iven by Bent (1922). Other d a t a have been publ ished by Ol ive r (1955) and W i l l e t t (1919) f o r o t h e r i s l ands . When bo i l ed , t h e egg was f u l l y a s p a l a t z b l e a s a h e n ' s egg and d i d not have the f i s h y odor o r t a s t e t h a t a r e a s soc i a t ed wi th the eggs of many o t h e r s e a b i r d s . The yo lk was a pa l e yellow. The white of t h e Mutton B i r d ' s egg i s l i k e t h a t of the hen ' s egg. It i s not su r - p r i s i n g t h a t t h e Maoris of New Zealand p r i z e t he eggs a s we l l a s t h e f l e s h of o t h e r shearwaters as food. Sex Determinat ion Since theshearwaters e x h i b i t no e x t e r n a l sexual dimorphism we used the method used by Seiventy (1956a) i n sexing p e t r e l s and shear- : ,~a t e r s by an examination of t h e c loaca . This method i s app l i cab le during the per iod of sexual a c t i v i t y . The d i f f e r e n c e between t h e sexes l i e s i n t h e g r e a t d i l a t i o n of t h e c loaca a s soc i a t ed wi th t h e swel l ing of t h e oviduct of t h e female, t o al low f o r t h e passage of t h e Large egg. We examined a s e r i e s of b i r d s and found t h e method easy and apparent ly accura te . To check t h e sexing, an incubat ing b i r d determined t o be a male by t h e c loaca1 examination was c o l l e c t e d ; d i s s e c t i o n proved t h e d iagnos is t o be c o r r e c t . F?e examined s i x b i r d s from nes t s soon a f t e r the egg was deposited; a l l six were males. This was evidence t h a t the male takes par t i n incubation and probably i n i t i a t e s it. Three males were banded which were incubating eggs, and in one case a female replaced the,male a f t e r s i x days. Unfortun- a te ly , the other two nes t s were accidentally destroyed. It i s cer ta in t h a t both male and female normally take par t i n incubation. The male may be the one of the pa i r t o excavate the burrow, but no sex deter- mination was made of the few birds seen digging burrows. More obser- vations a r e needed t o determine the time spent on the nes t by each sex and the number of times changes a r e made during the en t i r e period of incubation. The door and a window of our cabin faced the cleared area, giving us an unexcelled opportunity t o observe, by means of f l ash l igh ts and e l e c t r i c l i gh t s , the a c t i v i t i e s of the birds a t a l l hours of the night. Here we could repeatedly record the time of t h e i r a r r i v a l and departure and note the d e t a i l s of t h e i r behavior. During the day the shearwaters were not i n evidence on the is land; a l l but those incubating i n t h e i r burrows were scattered, feeding out a t sea. Some were seen by various observers more than a hundred miles from the colony, They seem t o be widely dispersed i n small groups but have been seen concentrated i n very la rge numbers, sometimes with Noddy Terns, i n places where food has abundant. The Wedge-tailed Shearwaters do not feed on f i s h t o any great extent. The food, judging from stomach examinations, i s ch ie f ly cephalopods such a s squids, shrimps, and o ther small crustaceans which a r e caught near the surface of the water. Far out a t sea s ingle individuals o r small groups of 2 t o 5 may be seen seeking food and occasionally s i t t i n g on the water. The shearwaters a r e expert f l i e r s and with t h e i r long narrow wings maneuver expertly a s they skim closely over the waves with l i t t l e movement of t h e i r wings; t h e i r f l i g h t resembles tha t of the albatrosses, but with more flapping. On a typ ica l evening in December the Noddy Terns were the f i r s t t o return; a few of them would be seen going t o o r from the island a t any hour of the day, but by h:30 p.m. the vanguard of the great masses of t e rns coming t o the Heron Island rookery f o r the night had arrived. Some of the birds came in a s s ing l e individuals, but most of them were in groups of t en o r more. By 7:00 p.m, the t e rn s were a r r iv ing by the thousands a l l along the eastern s ide of the island -- a s many a s 350 per minute within 30 meters of the beach. A t 7:45 p.m. the l i g h t was growing dim and suddenly there was an awe-inspiring roar of wings: the shearwaters had arr ived off shore. Thousands of them were c i rc l ing and f ly ing about before venturing inland. A few minutes l a t e r they would f l y over l i k e a swarm of huge bats. They continued t o f l y back and fo r th over the en t i r e nesting area of the island. A t t he c lear ing near t he camp a few minutes a f t e r 8:00 p.m. a dozen o r more shearwaters c i rc led high above t he t r e e tops. It was too dark t o see the d e t a i l s of t h e nest ing area without l i gh t s , but the bi rds were darkly si lhouetted against t he s t a r l i t s b above. The birds ut tered no ca l l s . A s they c i rc led and came nearer and nearer t o the ground they seemed t o be searching f o r a proper place t o land near t h e i r burrows. Around 8:30 p.m. t h e f i r s t b i rd would l i t e r a l l y drop t o the ground with a d i s t i n c t thump in a resounding pancake landing, withdrawing t he f e e t and folding t he wings a t about l$ meters above ground. It did not land on i ts f e e t nor did it break i t s down- ward speed by using i t s t a i l and wings effect ively . (Odd b i rds crashed i n to l ighted windows.) The birds were not stunned but, l inger ing long enough t o get t h e i r bearings, they scooted towards the entrance of a burrow where they might be met by t h e i r mates. A t t h e proper burrow the two birds seemed t o exchangs subdued c a l l s of recognition. One newly-arrived bi rd appeared t o be feeding i t s mate by regurgitat ion, but we were unable t o observe t h e t r ans f e r of t he food. The t w o b i rds came close together and one of them repeatedly ran i t s beak through the feathers of t h e neck and head of i t s mate. This behavior may have been a par t of the courtship performance. A t such times a pungent o i l was emitted from the n o s t r i l s a s occurs i n other pe t re l s . Soon other b i rds made s imilar landings i n quick succession, and the majority of them joined t h e i r mates, not i n the burrows as might be expected but on t h e open ground where they remained f o r the night. Courtship including copulation usually took place not in the burrows but on open ground. The birds do not stand upright on t h e i r f e e t but r e s t t h e i r bodies f l a t on the sand. A b i rd entering a wrong burrow was vigorousxy ousted by t he tenant which obviously was not i t s mate. This ousting was accompanied by loud yowls and v io len t flappings of wings. A t t h i s time t he c a l l s and weird sounds of the birds made the night hideous and ghostly. They came from thousands of birds i n every par t of t h e nest- ing area of the whole is land, The c a l l s were not bird-l ike and not musical but were high-pitched cat-l ike squal ls mingled with low- - pitched murmurs. A t times t h e i r c a l l s resembled those of cows and t h e i r calves, and again it was l i k e a l i v e l y and s p i r i t e d ca t serenade. The s i lence of day was rudely broken, a s darkness descended, by t h e i r weird dolorous wails. The chorus of thousands of shearwaters mingled with t he high- pitched c a l l s of t he noddy t e rn s i n t h e i r wooded rookery was kept up throughout t h e night without any marked intermission. The birds were s t i l l going strong a t 5:OO a.m., but soon t he r ea f t e r t he volume of sounds began tapering of f . There was much a c t i v i t y among the shear- waters, the bi rds running rapidly and awkwardly, scooting over t he ground with t h e i r wings upheld t o balance themselves. Evidently with t h e i r heavy bodies and wing spread of a meter it was d i f f i c u l t t o take off i n a r e s t r i c t e d area. Instead there would be a stampede of b i rds rushing along t h e ground t o the shore along well-defined paths. Some of the bi rds i n t h e i r confusion banged against our camp with such force t ha t it was surpr is ing t h a t no dead o r stunned birds were found on Heron Island. The exodus was rapid and by 5:30 a.m. no birds were seen on the breeding grounds. The thousands of shearwaters were o f f f o r another day on t h e i r hunting grounds a t sea. Calls We were par t icu la r ly interes ted i n the Mutton Bird because of the extent t o which i t s breeding and nesting behavior pa ra l l e l t h a t of Leach's Pe t re l , Oceanodroma leucorhoa ( ~ i e i l l o t ) , which has been studied f o r many years a t the Bowdoin Sc i en t i f i c Sta t ion a t Kent Island i n Canadals Bay of Fundy (w.A.o. Gross, 1935; Grif f in , 1940; A -0. Gross, 1947; Huntington, 1962.) Actually, although members of the same order ( ~ r o c e l l a r i i f o m e s ) , the two birds a r e i n d i f fe ren t famil ies ( ~ r o c e l l a r i i d a e - Shearwaters and Fulmars, and Hydrobatidae- Storm pe t re l s ) which share many character is t ics , including nesting underground on offshore islands, laying a s ingle egg, going and coming by night, feeding a t sea, c a l l i ng on the breeding grounds, the sexes being a l i k e externally, and e ject ing a stomach o i l of charac te r i s t i c odor a The c a l l s of Leach's P e t r e l have been recorded by Huntington, Ph i l i p D. Walls, Lowry C. Stephenson, and D. ~ a r r y May. This pe t r e l makes a " f l i gh t c a l l N heard a t - n i g h t over the nesting grounds and occasionally a t sea, and a "burrow callI t o r "purring c a l l n produced i n the burrow. The purring c a l l may be rarely produced on the wing, and the f l i g h t c a l l i s commonly produced i n the burrow. While t h e f l i g h t c a l l i s produced somewhat i r regular ly , t he purring c a l l i s produced over and over again by an undisturbed bird. When it is heard from a burrow, usually two birds a r e present, and the c a l l i s of ten heard a s a duet (palmer, 1962, p. 228). The f l i g h t c a l l con- s i s t s of two d i s t i nc t i ve staccato phrases, separated by a brief pause able 11); it var ies great ly i n pi tch and pattern de ta i l s . The Mutton Bird, on the o ther hand,produces a moan-like c a l l which var ies in p i tch from one individual t o another, but i s too simple t o a.llow var ia t ion i n pattern. It is made by birds ly ing on the ground and by birds i n the burrow. It may sound l i k e a cater- wauling, a howl, a low moan, and during f igh t ing l i k e a snarl . The birds a r e quiet whenever they enter a l ighted area, and we never heard them ca l l ing a t sea o r on the wing. Recordings were made of Heron Island Mutton Birds i n the v i c in i t y of the laboratory building of the Great Barrier Reef Committee on October 14, 1960, with a Magnecorder PT~-BN and a PT~BAWZ tape recorder and an Electro-Voice 630 microphone around 10:OO p.m. a t 3 3/4 inches/ second. Recordings of Leach's Pe t r e l s were made on Kent Island, Grand Manan, on May 25, 1962, around 10:45 p.m. with a Magnemite Recorder 610-EV, and Electro-Voice 630 microphone and a 30-inch parabolic r e f l ec to r a t 15 inches/second; other recordings were made on G u l l Is land, 20 miles south of S t . John's Newfoundland, a t 1:45 a.m. on August 14, 1962. Sound spectrograms were prepared on a Kay Vibralyzer vibrat ion frequency analyzer,and time-frequency data a r e taken from those preparations, Character is t ics of Mutton Bird and Leach's P e t r e l c a l l s a r e shown in Table 11. Call .- Mutton B i r d Leach's Pe t r e l Fl ight c a l l Leach's Pe t r e l Burrow c a l l ---- Duration - 1-29 seconds ( ~ a n g e 1.13 - 1.47) Mean of 5 c a l l s 1.02 seconds (Range ,8 - 1.2) Mean of 5 calls 2.5 seconds between clucks (1 c a l l measured) Frequency Span I General descr ip t ion 88 t o over 8800 cps with most sound energy between 615 and 4100 cps - -- -- -- Measurements of fundamental:- Mean of 5 s t a r t s 279 cps (225 - 315) of 5 peaks 419 cps A s e r i e s of 10 or 11 rapidly emitted notes, usually i n the follow- ing pattern:. - -- -- C a l l v a r i e s from a low moan t o a harsh s n a t l Purring:. up t o 6500 cps with most sound energy below 2200 cps i n a har- monic pattern. Ascending sound: 250-570 cps. Cluck: 88 t o over 8800 cps i n a harmonic pat tern (270 - 500) Mean of 5 ends 297 cps (180 - 360) I There a r e usually 2 harmonics , A prolonged purring in terrupted periodi- ca l l y ( a f t e r 56 notes i n one case) by the ascending sound of indrawn breath sad a sharp d u c k The nesting season of the Wedge-tailed Shearwater var ies in the d i f fe ren t par t s of i t s extensive l a t i t u d i n a l range. I n the northern colonies the time i s i n the northern spring, while i n the southern Pacific it i s i n the southern spring ( ~ u r ~ h y , 1951). A t Heron Island the f i r s t b i rd ms seen on October 8th and t h e f i r s t egg on December 15th. Egg-laying was a t i t s height a t the end of December. The incubation period of the Wedge-tailed Shearwater i s somewhat l e s s than two months, while fledging requires a t l e a s t three months, according t o Oliver (1955). We a r e indebted t o M r . H. F s Manning f o r information concerning the s t a tu s of the shearwaters on Heron Island a f t e r our departure. A few of the adul t b i rds l e f t i n March, 1961, but most of the adul t s do not usually leave u n t i l May. The birds a r e extremely noisy before t h e i r departure, and on the following day a l l i s deathly quiet . The young a r e deserted i n t h e i r burrows, where they remain u n t i l they are able t o s h i f t f o r themselves. The Short-tailed Shearwater does not acquire sexual maturity u n t i l s i x o r more years of age (Serventy, l956b). As a s imilar period may ex i s t f o r the Wedge-tailed Shearwater, a large portion of the birds present on Heron Island may be non-breeding individuals. Summary Wedge-tailed Shearwaters nesting a t Heron Island were observed from t h e i r a r r i v a l on October 8, 1960, u n t i l January 1, 1961. Measure- ments of f i v e unsexed l i v ing specimens and ten eggs were obtained. Widespread egg-laying began abruptly on December 15th. Hany eggs were l a i d on the ground, but were not incubated. Nest-building, nightly a r r i v a l s and departures, courtship, copulation, and c a l l s were observed and described. Sowd spectrograms of the c a l l s were compared with those of another tube-nose, Leach's Pe t re l , and found t o be much simpler and l e s s variable. Li te ra tu re Cited Bent, A . C. 1922. L i fe h i s t o r i e s of North American pe t r e l s and pelicans and t h e i r a l l i e s . Bull. U, S. Nat. Mus. 121: 1-343. Davidson, M. E. M. 1931. On the breeding of Puffinus chlororhsmchus i n t h e Tonga group. Condor 33: 217-218. Fosberg, F. R., R. F. Thorne, and J. Me Moulton 1961. Heron Island, Capricorn Group, Austral ia, A to l l Research Bul le t in 82: 1-16, Gri f f in , D. R. 194.0, Homing experiments with Leach's pe t re l , The Auk 57: 61-74 Gross, A. 0. 1947. Recoveries of banded Leach's pet re ls . Bird-Banding 18 : 117-126. Gross, W. A. 0. 1935. The l i f e h is tory cycle of Leachrs pe t r e l (~ceanodroma leucorhoa leucorhoa) on the outer i s l ands of t he Bay of Fundy. The Auk 52: 382-399 Howell, T. R., and G. A. Bartholomew 1961. Temperature regulation in nesting Bonin Island pe t r e l s , wedge-tailed shearwaters and Christmas Is land shearwaters. The A& 78: 343-354. Huntington, C . E, 1962. The population dynamics of Leachr s pe t re l , Oceanodroma leucorhoa, Abstracts of Papers, XIII th In t . Ornith. Cong. Loomis, L. M. 1923. The c l a s s i f i c a t i o n of the a lbat rosses , pe t r e l s and diving petre ls . The Auk 40: 596-602. Munro, G. C , 1944. Birds of Hawaii, Tongg Publishing Company, Honolulu, Hawaii. Mur);hy, R. C 1951. The populations of the wedge-tailed shearwater ( ~ u f f inus pacif i cus ) . American Museum Novitates 1512: 1-21. Oliver, W. R. B. 1955* New Zealand Birds. A. H. and A. W. Reed, Wellington, New Zealand. Palmer, R. S., Ed. 1962. Handbook of North American Birds, Vol. I. Yale Univ. Press, New Haven, Connecticut. 567 pp. Serventy, D. L. 1956a. A method of sexing pe t r e l s in f i e l d observations. Emu 56: 313-3Ue ------- 1956b. Age a t f i r s t breeding of the short-tailed shear- water, Puffinus tenu i ros t r i s , I b i s 98: 532-533. Wil le t t , Go 1919. Notes on the nesting of two little-known species of pe t re l , Condor 21: 60-61. Captions of Photos Upper l e f t - A c h a r a c t e r i s t i c pose of the Wedge-tailed Shearwater with its body r e s t i n g f l a t on the ground. The crossed wing t i p s extend t o near the end of the t a i l . Upper r ight - - The Fledge- t a i l e d Shearwater a t l e f t approaching i ts mate, which has j u s t emerged from the nes t ing burrow, Lower Left- The shearwater a t the l e f t has approached i t s mate which has come out of the nes t ing burrow. The b i rds a re b i l l i n g each other and running t h e i r beaks through the fea the rs of the neck, a p a r t of the cour tship performance. Lover r ight - - Three eggs of the Fledge-tailed Shearwater (Numbers 1-3 of Table 11) with an Austral ian sixpence, showing the r e l a t i v e s i z e of the l a rge eggs.