Growth of the Wedge-Tailed Shearwater in the Hawaiian Islands

GROWTH OF THE WEDGE-TAILED SHEARWATER IN THE HAWAIIAN ISLANDS

TED N. PETTIT, • G. VERNON BYRD,2 G. CAUSEY WHITTOW, • AND MICHAEL P. SEKI I'3 •Departmentof Physiology,lohn A. BurnsSchool of Medicine,University of Hawaii, Honolulu,Hawaii 96822 USA, and 2U.S.Fish and WildlifeService, P.O. Box87, Kilauea, Hawaii 96754 USA

ABSTRACT.--Growthstudies of a tropical seabird,the Wedge-tailedShearwater (Puffinus pacificus),were conductedover 3 yr at three locationsin Hawaii. Basicgrowth patternsof body dimensionsare described.The range of asymptotesand maximal recordedweights suggeststhat feeding and the availability of food may influence growth from year to year and in differentcolonies within the sameyear. Received15 September1982, accepted I September 1983.

GROWTHamong procellariiform chicks is just above sea level that comprise French Frigate characterizedby slow development,a long and Shoals in the northwestern Hawaiian Islands. Data flexible fledging period, large depositsof lipid for body-weight gain in Wedge-tailed Shearwater reserves, and achievement of a prefledging chicksfrom Manana Island, Oahu during 1972 (Shal- weight well abovethe adult's body weight, fol- lenberger1973) have alsobeen analyzedfor comparison. Morphological and developmental notes were lowed by a prefledging weight loss. These made throughout the growth period. Growth mea- growth characteristicsare consideredto be ad- surementswere obtained by separateparties of ob- aptationsto meager,distant, or fluctuatingfood serverson each island. A single personin each party resources (Lack 1967, 1968; Ricklefs 1968). was responsiblefor making a single set of observa- Few studies of tropical seabirds have ad- tions (body weight or body dimensions) to assure dressed intraspecific variations in the growth uniform measurements.Fledging successin Wedge- of nestlingsat different latitudesor in different tailed Shearwatersaverages 80% of hatched chicks colonies.Nelson's (1978) study of the Red-foot- (Byrd, Moriarty, and Brady unpubl.). The following ed Booby (Sulasula) in the GalapagosIslands measurements were obtained from chicks of known and at Christmas Island, Indian Ocean is a no- age(+ 1 day) that lived either beyond90 daysor were known to have fledged successfully. table exception.We present here the resultsof (1) Bodyweight: chicks were weighed on an Ohaus growth studiesof the Wedge-tailedShearwater triple-beambalance to ñ0.1 g (MananaIsland) or with (Puffinuspacificus), conducted over severalyears calibratedPesola spring scalesto + ! g (Kilauea Point at three different locations in the Hawaiian Ar- and Tern Island). Measurements were made either chipelago. 1-3 times a week (Manana Island and Kilauea Point) or daily (Tern Island). METHODS (2) Culmenlength: the bill was measuredwith calipers or dividers (+0.5 ram) from the tip of the upper Data were collected from three locations during mandible to the edge of the nasal skin covering the 1978-1980: Manana Island, Oahu (1978, 1979); Ki- bill. lauea Point, Kauai (1978, 1979, 1980); and Tern Is- (3) Winglength: wings were measuredwith a tape- land, French FrigateShoals (1979). Manana (Rabbit) measure(+2 ram) either with the wing straightened Island (21ø30'N,157ø40'W) is a small island lying ap- and extendedperpendicularly to the axisof the body, proximately 1 km off the southeasternshore of the from the most anterior point of the humerus at the main island of Oahu. Kilauea Point (22ø15'N, shoulderjoint to the tip of the phalanges(Manana 159ø30'W)is a peninsularising about45 m abovesea Island), or with the wing flattened, from the shoul- level on the northwestern coast of Kauai. Tern Island der joint to the tip of the longestprimary or to feath- (23ø52'N, 165ø18'W)is one of several small flat islands er sheathif primaries had not erupted (Kilauea Point). (4) Tarsuslength: the length of the tibia-fibula was measuredwith calipers (+0.5 ram) from the distal end of the tibiotarsusto the proximal end of the tibia • Present address: National Marine Fisheries Ser- (Manana Island). The tarsometatarsuswas measured vice, Honolulu Laboratory, Hawaii 96822 USA. on Kilauea Point accordingto Pettingill (1970).

103 The Auk 101: 103-109. January 1984 104 PETTITET AL. [Auk,Vol. 101

I,.- 3(30 -r

0 200

I00

10 20 30 40 50 60 70 80 90 I00 I10 AGE (days) ]Fig. 1. Growth in body weight of Wedge-tailed Shearwaterson Manana-Island, Oahu; Ki]auea Point, Kauai; and Tern Island, French Frigate Shoalsin 1978, 1979, and 1980.

(5) Middle toe length:the middle toe was measured to the point betweenthe middle rectriceswhere they with calipersor dividers (+_0.5mm) from the tip of emerge from the skin. the claw (Manana Island) or from the tip of the toe Each set of body-weight data was transferred to without the claw (Kilauea Point) to the proximal fold computer cards. Body-weight data for chicks un- in the webbing between the middle and lateral toe. dergoing prefledging weight recession have been (6) Tail length:the tail featherswere measuredwith omitted from computeranalysis. Logistic, Gompertz, dividers (+_2 mm) from the tip of the longest rectrix and yon Bertalanffy equationswere fitted to the data

TABLE1. Analysis of growth in the Wedge-tailed Shearwater.a

KR (100)/ Location Year n x K b A 4KA/9 t•o_9o A/w Fw A/Fw 0.444

Manana Is. 1972 -- 65 0.038 0.591 499 8.43 59.2 1.28 ------Manana Is. 1978 11 120 0.052 0.574 424 9.80 43.3 1.09 417 1.02 12.8 Manana Is. 1979 13 145 0.051 0.579 456 10.34 44.1 1.17 392 1.16 13.4 Kilauea Pt. 1978 37 393 0.045 0.588 440 8.80 50.0 1.25 429 1.03 12.7 Kilauea Pt. 1979 16 175 0.059 0.597 477 12.51 38.1 1.22 406 1.17 16.2 Kilauea Pt. 1980 23 346 0.049 0.583 454 9.89 45.9 1.16 426 1.07 12.8 Tern Is. 1979 14 621 0.043 0.595 503 9.61 52.3 1.29 440 1.14 12.5

' The yon Bertalanffygrowth equationis W - [A(1 - be •r)]3,where W is mass(g), K is the growth constant(days •), e is the baseof the natural logarithms,T is time (days),A is the asymptote(g), and b is a constantthat translatesthe time axis such that time (T) is equal to zero at the inflection point. Other growth parametersare 4KA/9, the maximal amount of absolutegrowth (g.day •); t•0m (2.25/K), the amount of time required to grow from 10%to 90% of the asymptoticweight; w, the mean adult weight (390 g); Fw, the fledging weight (g); KR(100)/0.444,the maximalinstantaneous growth rate (as a percentageof adult weight), which occursat the inflection point of the growth curve. January1984] Growthof Shearwaters 105

4OO

300-

250

2OO

AGE (DAYS) AGE (DAYS)

3OO

250

,o & •b •'o •o do •o do •o ,4o •o •b •o •'o do do •o do ;o ,oo•-- AGE (DAYS) AGE (DAYS)

Fig. 2. Growth of body dimensions of Wedge-tailed Shearwaterson Manana Island, Oahu in 1979. by an iterative method and analyzed for goodness- 0.059/day, and the asymptotesranged from 424 of-fit by a FORTRAN program for nonlinear least- g to 503 g. squaresregression (Smond, Pettit, and Whittow un- Figure 2 presents the linear measurements publ.) implemented by an IBM 370/145 computer. (culmen, wing, tibia-fibula, middle toe) of The yon Bertalanffyequation (Fabens1965) provided Manana Island shearwaters in 1979. Figure 3 the best fit in all cases.Summary statisticsof growth patternsare developedfor eachpopulation as a whole. presents the linear measurementsof shearwaters at Kilauea Point in 1980. The linear body RESULTS dimensions cannot be compared directly (ex- cept for culmen length) due to differencesin Growthanalysis.--The fitted von Bertalanffy measurement techniques (see Methods). A growth curvesfor shearwaterbody weight from summary of these data (Table 2) suggeststhat Manana Island, Kilauea Point, and Tern Island the asymptotefor leg growth (tarsometatarsus are presented in Fig. 1. The smooth curves and tibia-fibula length) is reached about age shown in Fig. 1 were generated by computer 50-60 days and before attainment of asymp- (Fabens 1965), and they are extended to the totes for other measured body dimensions. mean fledging period for the sample popula- Adult dimensionsof Wedge-tailed Shearwaters tion. Thus, the smoothedgrowth curvesdo not (Shallenberger 1973) are presented for compar- reflect the prefledging weight recession data, ison (Table 2). which were omitted from computer analysis. Table 3 presentsthe mean maximal recorded Although the curves vary in slope and form, body weights of chicks and their correspond- they are grouped according to the major vari- ing mean ages,the mean fledging weights, and ables, the growth rate constant (K) and the the mean fledging period for all sample pop- asymptotic weight (A). The von Bertalanffy ulations. Analysis of variance indicated no sta- growth parametersare presented in Table 1. tistical differencesamong the fledging periods, The mean K factor ranged from 0.038/day to but several significant differenceswere found 106 PETTITET AL. [Auk, Vol. 101

5O 0

400 •

,z,,• . ';,.::',::...,

80 0 I00 I10 AGE (DAYS) AGE (DAYS)

500

500 450 ;•;:;'?' • •o

;';"t:. - ' •,'i'•!t*?"' .'"i , •"i•'• ', •o • so ,.•,-.y,4': :'/'!:; ß .;:,.•;.,...,, 1•,','* ,.' ,, ,'o 2• •b 4'o •o 6'o 7• • •'o ,60 ,',o AGE (DAYS) AGE (DAYS)

Fig. 3. Growth of body dimensionsof Wedge-tailed Shearwatersat Kilauea Point, Kauai in 1980.X = tail length. amongother growth characteristicsfor the var- hatchling is initially fed stomachoil by regur- ious populations(Table 4). gitation from the adult. The stomachoil of pro- Developmentof thechick.--At hatching, the feet cellariiforms is high in energy content, aver- and the tarsi are flesh-colored, and the bill is a aging about 10 kcal/g (Warhamet al. 1976,Pettit light slaty color. Hatchlings are able to support and Whittow unpubl.). During the first 3-4 themselves and move about in the burrow nest- chamber after the first day. The primary down (protoptiles) may be quite variable but typical- TABLE2. Asymptotic linear body dimensions and ly is a very light grey, unlike the dark grey of corresponding ages of Wedge-tailed Shearwater the secondary down (mesoptiles), which ap- nestlings in Hawaii. peared at a mean age of 22.6 days + 3.7 (SD) (n = 23). Chicks are hatched with eyes closed, Length Age but the eyesopen generally within the first 24 Measurement (ram) (days) Adult a h. The egg tooth disappearedat an averageage Tibia-Fibula 80 -85 50 -60 of 13.6 + 1.6 days (n = 22), and pin feathers of Tarsometatarsus 45-50 50-60 50 the primary and secondaryflight feathers and Culmen 35-40 60-70 rectricesbegan to appear at a mean age of 34.9 Middle Toe days + 3.7 (n = 15). Nestlingsare coveredwith With claw 50-60 60-70 down until age 75-85 days. After 90 days of Without claw 50-55 60-70 age down may persist on the head, abdomen, Wing and neck. It is not uncommon for fledging Kilauea Point 275-300 100-110 297 Manana Island 310-325 80-90 shearwatersto have down remaining on these areas after departure from the nesting colony. Tail 100-130 100-110 138 Feeding and weight gain.--The shearwater Data from Shallenberger (1973). January 1984] Growthof Shearwaters 107

TABLE3. Growth characteristicsof Wedge-tailed Shearwaters.a

Maximal weight Age Fledging weight Fledging age Population Year (g) (days) (g) (days) Manana Island 1978 497.0 + 33.0 72.3 + 16.1 417.0 + 69.8 102.0 + 6.1 (11) (11) (8) (8) Manana Island 1979 493.0 + 87.9 79.4 + 5.8 392.2 + 61.8 100.0 + 6.1 (13) (13) (10) (10) Kilauea Point 1978 565.7 + 43.0 86.8 + 8.9 428.8 + 54.1 109.2 + 3.2 (37) (37) (33) (33) Kilauea Point 1979 554.4 + 64.0 73.9 _+ 14.2 405.5 + 24.8 107.1 + 2.8 (16) (16) (9) (9) Kilauea Point 1980 532.5 + 46.7 85.1 + 11.1 426.1 + 51.9 106.2 _+ 4.6 (23) (23) (23) (23) Tern Island 1979 573.9 + 51.3 68.4 _+ 11.8 439.6 + 32.5 104.4 + 4.8 (14) (14) (14) (14) Values are presentedas mean _+SD; (n) = sample size. days, the adult initiates the feeding processby weighed approximatelyevery 12 h for a week "actually picking up the chick'sbill" (Shallen- before fiedging and departure, feeding oc- berger 1973).Thereafter, the chick will peck at curred on 66% of the days (1.3 days per feed- the bill and throat of the parent and stimulate ing + 0.4),and theaverage weight gain for each regurgitation. Examination of regurgitated feeding session was 40.0 g + 11.4 (n=56). stomach contents of the chick indicated that Burger (1980) has summarized data showing partially digested squid and stomachoil com- that a prefledgingweight lossamong procel- bined and then larger piecesof whole squid lariiforms occurs both in species with and and fish are fed to the chick. without desertion periods. The 10-15% pre- Although the feeding intervals of some fledging weight loss in the Wedge-tailed shearwater chicks may be quite long and vari- Shearwater is similar to that of other speciesof able, judging by extended weight-lossperiods, Puffinus(Warham 1958, Richdale 1963, Harris the daily weight measurementsof shearwater 1966). The absence of a desertion period has nestlings on Tern Island (1979) indicated that also been reported for Audubon's Shearwater the mean feeding interval (the time between ( Puffinuslherminieri, Harris 1969). recorded weight gains) was 1.7 days + 0.4 (range 1-11 days) for 432 observationsof 10 DISCUSSION chicks. Some feedings are small and result in no weight gain; therefore, this assessmentis Growth and geographicallocation.--Nelson likely to be an underestimation.Among eight (1978) reported that growth in the Red-footed shearwaters at Kilauea Point (1980), which were Booby(Sula sula) is slower among chicksin the

TABLE4. Analysis of variance: comparisonof maximal recorded weight (a), age at maximal weight (b), and fledging weight (c). S = significant difference (F-test, P < 0.05), NS = nonsignificant difference.

Manana Manana Kilauea Kilauea Kilauea 1978 1979 1978 1979 1980

Population a b c a b c a b c a b c a b c Manana 1978 ------Manana 1979 S S NS ------Kilauea 1978 S S NS NS S NS ------Kilauea 1979 S NS NS NS S NS NS S NS ------Kilauea 1980 S NS NS S S NS NS NS NS NS NS NS ------Tern 1979 S NS S S S S NS NS NS NS NS S NS NS S 108 PETTITET AL. [Auk,Vol. 101

GalapagosIslands than at ChristmasIsland (In- ACKNOWLEDGMENTS dian Ocean), and he attributed this difference Data were collectedby severalemployees and vol- to climatic conditions and food supply. If unteers with the U.S. Fish and Wildlife Service. We growthrate is a functionof foodavailability, greatly appreciatethe field effortsof S. Schulmeister, then the variations in growth parameters may R. Schulmeister,D. Moriarty, N. Reed, B. Brady, R. reveal differences in foraging successand/or Ittner, and H. Seshiki.We thank Roger Simond, De- prey species(energy content)among different partment of Physiology, University of Hawaii, for island breeding populations. In general, there help with computeranalysis of growth patterns.This does not appear to be a simple correlation be- study was supported in part by a National Science tween growth parametersand geographicallo- Foundation Grant (PCM 76-12351-A01) and Sea Grant College Program (NOAA) Grant N1/R-14 adminis- cation. The analysisof shearwatergrowth (Ta- tered by Dr. G. C. Whittow. We are grateful to the bles 1, 3), however, suggeststhat nestlingsfrom Department of Land and Natural Resources,Division Kilauea Point and Tern Island achieved greater of Forestryand Wildlife, State of Hawaii, for grant- maximal weights, fledging weights, asymptotic ing a permit to conductresearch on Manana Island. weights, and longer fledging periods than did those from Manana, although the differences were not alwayssignificant (Table 4). The fluc- LITERATURE CITED tuation and variability of food resourcesare BURGER,J. 1980. The transition to independenceand unknown for tropical Hawaiian waters, al- post-fledgingparental care in seabirds.Pp. 367- though they are currently under investigation 447 in Biology of marine animalsVol. 4 (J. Burg- (see Grigg and Pfund 1980). Fish (Mullidae, er, B. L. Olla, and H. E. Winn, Eds.). New York, Carangidae)and squid (Ommastrephidae)make Plenum Press. up the greater part of the shearwaterdiet (Har- FABENS,A.J. 1965. Properties and fitting of the von rison and Hida 1980). The various feeding Bertalanffygrowth curve. Growth 29: 265-289. grounds and distancesto shearwaterbreeding GRIGG,g. W., & g. T. PFUND (Eds.). 1980. Status of colonies are unknown. resource investigations in the Northwestern Growth and annual variation.--Harris (1966) has Hawaiian Islands. Honolulu, Hawaii, Univ. Ha- shown that the average growth curves for the waii Sea Grant College Prog. HARRIS,M.P. 1966. Breeding biology of the Manx Manx Shearwater(P. puffinus)during 3 yr (1955, ShearwaterPuffinus puffinus. Ibis 108: 27-33. 1963, 1964) vary little for the population resid- ß 1969. Foodas a factor controlling the breeding on Skokholm Island, Wales. Data for the ing of Puffinusl'herrninieri. Ibis 111: 139-156. Wedge-tailed Shearwater over 3 years (1978- HARRISON, C. S., & T. S. HIDA. 1980. The status of 1980) at Kilauea Point, however, display con- seabird research in the Northwestern Hawaiian siderablevariation in the fitted growth curves Islands. Pp. 17-32 in Statusof resourceinvesti- (Fig. 1) and growth parameters(Table 1). For gationsin the northwesternHawaiian Islands(R. example, the maximum instantaneousgrowth W. Grigg and R. T. Pfund, Eds.). Honolulu, Ha- rate occursat the inflection point of the growth waii, Univ. Hawaii Sea Grant College Progr. curve (Hussell 1972). It ranged from 12.7% in HU$$ELL,D. J.T. 1972. Factorsaffecting clutch size in arctic passetines.Ecol. Mongr. 42: 317-364. 1978 to 16.2%in 1979 for growth data from Ki- LACK,D. 1967. Interrelationships in breeding ad- lauea Point. Thus, a 31% increasein this growth aptationsas shown by marine birds. Pp. 3-31 in parameter occurred in two consecutivebreed- Proc. 14th Ornithol. Congr. (D. W. Snow, Ed.). ing seasonsamong the nestlingsmeasured. Al- Oxford, Blackwell Scientific. though the seasonaland annual variation in ß 1968. Ecologicaladaptations for breeding in availability of shearwater prey species in birds. London, Methuen. Hawaiian waters is not well understood, the NELSON,J. B. 1978. The Sulidae: gannetsand boo- fluctuation in some prey fishes has been re- bies. Oxford, Oxford Univ. Press. ported (see Grigg and Pfund 1980). Thus, vari- PETTINGILL,O. S. 1970. Ornithology in the labora- ations in the observed growth patterns may be tory and field. Minneapolis, Minnesota, Burgess Publ. Co. related to fluctuations in food resources. Some RICHDALE,R. E. 1963. Biology of the Sooty Shear- Hawaiian seabirds, possibly including the water. Proc. Zool. Soc. London 141: 1-117. Wedge-tailed Shearwater, have apparently RICKLEES,R. E. 1968. Patterns of growth in birds. evolved breeding patterns to fit the seasonal Ibis 110: 419-450. abundance of juvenile fishes and fish larvae SHALLENBERGER,g.J. 1973. Breedingbiology, hom- (Harrison and Hida 1980). ing behavior,and communicationpatterns of the January1984] Growthof Shearwaters 109

Wedge-tailed Shearwater Puffinuspacificus chlo- , R. WATTS, •r R. J. DAINTY. 1976. The com- rorhynchus.Unpublished Ph.D. dissertation.Los position, energy content and function of the Angeles, Univ. California. stomach oils of petrels (Order, Procellari~ WARHAM,J. 1958. The nesting of the Shearwater iformes). J. Exp. Marine Biol. Ecol. 23: 1-13. Puffinuscarneipes. Auk 75: 1-14.

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