ASPECTS OF THE BREEDING BIOLOGY OF THE GENTOO PENGUIN PYGOSCELIS PAPUA AT VOLUNTEER BEACH, FALKLAND ISLANDS, 2001/02

ASPECTS OF THE BREEDING BIOLOGY OF THE GENTOO PENGUIN PYGOSCELIS PAPUA AT VOLUNTEER BEACH, FALKLAND ISLANDS, 2001/02 HELEN M. OTLEY, 1 ANDREA P. CLAUSEN, 1 DARREN J. CHRISTIE 1 & KLEMENS PÜTZ 2 1 Flklnds Conservtion, PO Box 26, Stnley, Flklnd Islnds FIQQ 1ZZ, UK (heleno@southcom.com.u) 2 Antrctic Reserch Trust, PO Box 685, Stnley, Flklnd Islnds FIQQ 1ZZ, UK 167 Received 4 My 2004, ccepted 1 Februry 2005 SUMMARY OTLEY, H.M., CLAUSEN, A.P., CHRISTIE, D.J. & PÜTZ, K. 2005. Aspects of the breeding biology of the Gentoo Penguin Pygoscelis ppu t Volunteer Bech, Flklnd Islnds, 2001/02. Mrine Ornithology 33: 167 171. The breeding biology of 14 pirs of Gentoo Penguins Pygoscelis ppu ws studied t Volunteer Bech, Flklnd Islnds during 2001/02. Breeding commenced in October nd the men htch dte for the first-lid egg ws 6 December ± four dys. The brood period lsted 27 dys, nd chicks fledged from the first week of Februry onwrd. The sexes shred incubtion nd brood duties eqully. Men minimum nd mximum forging trip lengths were 2.0 3.0 dys nd 0.7 1.8 dys during the incubtion nd brood periods respectively. Timing of breeding nd breeding success t Volunteer Bech were similr to those reported t other colonies in the South Atlntic Ocen/Antrctic Peninsul region. In contrst, the comprtively long forging trips during incubtion nd brooding were similr to those reported for Gentoo Penguins breeding in the southern Indin Ocen. Keywords: Gentoo Penguin, Pygoscelis ppu, Flklnd Islnds, breeding biology INTRODUCTION The Gentoo Penguin Pygoscelis ppu hs one of the most extensive ltitudinl rnges of ny penguin species, breeding from the Crozet Islnds (46 S) in the southern Indin Ocen to Petermnn Islnd (65 S) on the Antrctic Peninsul (Woehler 1993). Despite the rnge of climtic conditions nd mrine systems, ll studied colonies cross the bird s rnge showed severl similr breeding prmeters (Willims 1995). Those prmeters included synchronous lying of two eggs, equl shring of chickrering, nd forging trips of fewer thn four dys during the incubtion nd brooding periods. However, significnt differences hve been identified in the timing of breeding nd the forging strtegies of birds in colonies in the southern Indin nd Pcific Ocens s compred with those in the South Atlntic Ocen/Antrctic Peninsul region (Trivelpiece et l. 1987, Bost & Jouventin 1990, Willims 1990, Willims & Rothery 1990, Bost & Jouventin 1991, Robinson & Hindell 1996, Quintn & Cirelli 2000). Birds in the southern Indin Ocen, such s t Mrion, Crozet nd Kerguelen Islnds, commence breeding during the ustrl winter, with filed breeders often re-lying during spring, when birds in South Atlntic nd Antrctic Peninsul colonies re first producing eggs (Bost & Clobert 1992). Higher breeding success hs been reported in colonies in the South Atlntic Ocen/Antrctic Peninsul region s compred with colonies in the southern Indin Ocen (Willims 1990, Quintn & Cirelli 2000). A 10-yer record of breeding success in number of colonies in the Flklnd Islnds suggests tht breeding success there is similr to tht observed in South Georgi (Pütz et l. 2001, Clusen & Pütz 2002). However, breeding biology beyond nnul monitoring of breeding success hs not been studied in the Flklnd Islnds, despite the islnds holding the lrgest popultion of the northern nominte subspecies (Willims 1995). The present study describes the timing of the incubtion, brood nd fledge periods, nd forging trip lengths of the Gentoo Penguin in the Flklnd Islnds. METHODS The study ws conducted t Volunteer Bech on the estern cost of Est Flklnd Islnd (51 29xx S, 57 50xx W), which receives 1000 visitors ech summer (HMO, pers. obs.). The 1000 breeding pir colony hs been subject to the legl collection of eggs by people for mny decdes, with c. 150 eggs removed in lte October 2001 (G. Smith pers. comm.). Observtions begn during erly egg incubtion (the first week of November) when 14 pirs were identified by the presence of one bird on nest nd second bird demonstrting nest building or breeding displys. The study commenced fter erly breeders hd lid eggs. To reduce disturbnce, only pirs breeding on the edge of the colony were selected. Although breeding success in Pygoscelis penguins is pprently not ffected by nest loction (Giese 1996, Brbos et l. 1997, Quintn & Cirelli 2000), the 14 pirs selected were likely to hve begun breeding up to one week lter thn the more centrlly locted pirs (HMO, pers. obs.). We used pole to cpture the non-incubting prtner t ech nest by the nkle; the bird ws then mrked with length of dhesive tpe wrpped round the bse of flipper. Upper bill length (versus lower bill length, s cited in Willims 1990) nd bill depth were mesured to the nerest 0.1 mm; body mss ws mesured to the nerest 0.1 kg. It ws not known if the mrked bird hd recently undertken long incubtion shift before cpture. In mid-jnury,

168 Otley et l.: Breeding biology of the Gentoo Penguin in the Flklnd Islnds the unmrked prtners in eight of the 14 selected pirs were cptured nd mesured. Six prtners could not be cptured without cusing disturbnce to the colony. In the eight pirs in which both birds were mesured, the prtner with the lrger bill ws ssigned s the mle (Willims 1990). In the remining six pirs in which the unmrked bird ws not cptured, birds with bill length greter thn 57 mm were ssigned s mle. Between 31 October 2001 nd 11 Jnury 2002, fter which ll study chicks hd entered crèche, nests were checked dily t dwn (04h15 06h15) nd dusk (19h00 21h30) for the presence of mrked nd unmrked birds, eggs nd chicks. The intervl between checks vried between eight hours nd 16 hours, depending on the times of sunrise nd sunset. Becuse exct times of chngeovers were not recorded, the minimum (ssuming tht the chnge hd occurred just before the check) nd mximum (ssuming tht the chnge hd occurred just fter the previous check) durtions for ech trip were clculted. Becuse study pirs were lredy incubting eggs when observtions commenced, the incubtion period ws recorded for two lte-breeding pirs whose eggs were lid fter observtions hd commenced. Nests were pproched using recommended methods (Giese 1998), nd bmboo pole ws used to lift the incubting bird slightly so s to ssess the number of eggs or chicks (or both). Just before crèche formtion, we mesured bill length nd depth nd body mss of three chicks from double-chick study pirs nd three chicks from single-chick study pirs ged 22 31 dys. Counts (verge of three vrying less thn 10%) of incubting pirs nd chicks were mde every five dys between 2 November 2001 nd 29 Mrch 2002. If not otherwise stted, ll vlues re given s men ± stndrd devition (SD). The Student t-test ws used fter checks for normlity nd vrince. TABLE 1 Sttisticl differences between men bill length nd depth of 12 mle nd 10 femle dult Gentoo Penguins nd the body mss of seven mle nd six femle dult birds during erly incubtion. Also comprison of bill dimensions nd body mss of three chicks from single-chick clutches nd three chicks from double-chick clutches ged 22 to 31 dys s compred with the men dult dimensions t Volunteer Bech Men ± SD (n) Mle Femle Significnce Chick Percent of men dult size Bill length (mm) 60.5±2.3 (12) 54.1±1.9 (10) t 11 = 4.84, P < 0.001 33.7±3.2 (6) 62 Bill depth (mm) 24.8±4.0 (12) 23.2±2.6 (10) t 11 = 0.29, P=0.778 16.6±1.6 (6) 72 Body mss (kg) 7.0±0.7 (7) 6.6±0.6 (9) t 12 = 1.87, P=0.086 3.2±0.7 (6) 48 SD = stndrd devition. TABLE 2 Timing of breeding ctivities nd forging trip lengths undertken by 14 incubting Gentoo Penguin pirs observed over period of up to 39 dys. Men minimum nd men mximum vlues re ± stndrd error Pir Cpture Clutch Incubtion Mle Femle Comprison Eggs Htching dte ly observed Trips Men Men Trips Men Men of mle (n) dte dte (%) (n) min mx (n) min mx nd femle Chick 1 Chick 2 (h) (h) (h) (h) 1 1 Nov 24 Oct 72 6 36 56 7 31 55 t 11 =0.81, NS 2 29 Nov 30 Nov 2 8 Nov 28 Oct 67 6 37 58 8 55 77 t 12 =1.69, NS 2 3 Dec 4 Dec 3 2 Nov 1 Nov 97 5 86 112 6 69 92 t 9 =0.48, NS 2 10 Dec 12 Dec 4 1 Nov 27 Oct 95 6 44 66 5 59 80 t 9 =0.33, NS 2 2 Dec 7 Dec 5 1 Nov 28 Oct 90 6 52 76 8 55 74 t 12 =2.79, P=0.02 2 3 Dec 6 Dec 6 1 Nov 28 Oct 90 5 63 86 7 35 59 t 10 =0.57, NS 2 3 Dec 6 Dec 7 1 Nov 29 Oct 87 6 36 52 5 73 97 t 9 =2.09, NS 2 4 Dec Not htch 8 1 Nov 30 Oct 92 8 52 72 7 42 60 t 13 =1.70, NS 2 6 Dec 7 Dec 9 3 Nov 1 Nov 92 7 38 58 5 59 82 t 10 =1.16, NS 2 8 Dec Not htch 10 2 Nov 1Nov 97 8 33 51 7 47 64 t 13 =0.79, NS 2 8 Dec 9 Dec 11 6 Nov 3Nov 79 5 68 96 8 43 73 t 11 =0.83, NS 1 8 Dec 12 1 Nov 1 Nov 100 8 32 55 7 34 55 t 13 =1.46, NS 2 9 Dec 10 Dec 13 1 Nov 1Nov 95 8 35 56 5 48 76 t 13 =1.34, NS 2 11 Dec Broken 14 9 Nov 8Nov 95 7 41 61 9 43 69 t 14 =0.09, NS 1 15 Dec 30 Oct ± 4 47 ± 4 68 ± 5 50 ± 3 72 ± 3 26 6 Dec ± 4 6 Dec ± 4 Lying dte of first egg extrpolted from n incubtion length of 37 d recorded in two dditionl nests. NS = nonsignificnt.

Otley et l.: Breeding biology of the Gentoo Penguin in the Flklnd Islnds 169 RESULTS Study pirs Bill lengths for the ssigned mles nd femles were significntly different, but bill depths were not (Tble 1). Body mss in erly incubtion ws not significntly different between mle nd femle birds; the birds weighed between 6.0 kg nd 7.0 kg (Tble 1). Egg period Twelve of the study nests nd the two nests for which egg lying nd htching dtes were both recorded contined two eggs. The two other study nests ech contined single egg. The single eggs were not noticebly smller thn the eggs in two-egg clutches. In the two nests for which egg lying nd htching dtes were both recorded, the incubtion periods for the first egg were 36.5 dys nd 37.0 dys. Using period of 37 dys, the extrpolted lying dtes for the first egg in the study pirs fell between 24 October nd 8November, with men lying dte of 30 October (Tble 2). During the egg period, mles nd femles undertook forging trips of minimum durtion of 8 190 hours nd mximum durtion of 8 240 hours. In ll but one pir, no significnt difference between mle nd femle mximum forging trip lengths ws observed (Tble 2). The men ± stndrd error (SE) minimum nd mximum mle forging trip lengths were 47 ± 4 hours (2.0 dys) nd 68 ± 5 hours (2.8 dys) respectively, compred with the men ± SE femle minimum nd mximum forging trip lengths of 50 ±3hours (2.1 dys) nd 72 ± 3 h (3.0 dys; Tble 2). The men dte for the first htching of n egg in 14 nests ws 6 December ± four dys, with the first egg in study pir htching on 29 November, nd the lst on 15 December (Tble 2). Htching success ws 89%; one egg broke in the week before the htching of the other egg, nd one egg in ech of two clutches filed to htch. No nests were bndoned, nd no eggs were preyed upon. Brood period During the brood period, the femle of one pir did not return, nd the mle bndoned the two chicks fter nine dys. In the remining 13 pirs, mles nd femles undertook forging trips of minimum durtion of 8 72 hours nd of mximum durtion of 8 97 hours. In ll but one pir, no significnt difference between mle nd femle mximum forging trip length (Tble 3) ws observed. The men minimum nd mximum mle forging trip length ws 18 ± 3 hours (0.8 dy) nd 42 ± 6 hours (1.8 dys) respectively, s compred with the men femle minimum nd mximum forging trip length of 17 ± 2 hours (0.7 dy) nd 38 ±3h (1.6 dys) respectively (Tble 3). The 15 chicks tht survived the brooding period were brooded for between 21 dys nd 29 dys (men: 26 ± 2 dys; Tble 3). The brood period for eight chicks in four clutches in which both chicks survived to the end of the brood period ws not significntly longer s compred with seven chicks in nests where only one chick survived (t-test: t 13 = 0.33; P = 0.75). Fifteen of 23 study chicks (1.1 chicks/pir) survived to the end of the brood period. Filure becuse of bndonment occurred in one nest fter brooding shift of nine dys t the nest. Both chicks in two nests nd one of the two chicks in two nests died for unknown resons during the first 15 dys fter htching. Men body mss of two chicks from single-chick nests, one chick in nest in which the other chick died 10 dys fter htching, nd three chicks from twochick nests ged 22 31 dys old ws 3.2 kg. Bill dimensions were less thn 72% of men dult size t Volunteer Bech (Tble 1). Colony breeding success In mid December, 1103 ± 22 breeding pirs were present t Volunteer Bech. The 1371 ± 16 chicks present in the colony in erly Jnury begn to deprt to se in the lst week of the month (Fig. 1). By the third week of Mrch, no chicks were present. TABLE 3 Forging trip length undertken by 14 Gentoo Penguin pirs, nd chick survivl during brooding. Men minimum nd men mximum vlues re ± stndrd error Pir Trips Mle Femle Comprison Brood Age t (n) Men Men Trips Men Men of mle length deth min mx (n) min mx nd femle (d) (d) length (h) length (h) length (h) length (h) (t-test) 1 9, 10 2 8 21 40 7 14 32 t 13 =0.89, NS 8, 12 3 3 14 33 3 40 64 t 4 =2.27, NS 3, 6 4 7 21 42 7 11 34 t 12 =1.03, NS 29 15 5 5 47 113 5 15 37 t 8 =1.12, NS 25, 28 6 9 15 33 9 13 26 t 16 =1.18, NS 26, 28 7 9 20 41 10 12 32 t 17 =1.80, NS 28 8 8 23 45 8 14 31 t 14 =1.61, NS 26, 27 9 9 12 31 11 13 35 t 18 =0.77, NS 25 10 9 10 33 10 16 41 t 17 =1.23, NS 26, 27 11 8 18 40 10 19 42 t 16 =0.23, NS 27 12 9 13 30 12 15 36 t 19 =1.54, NS 26 10 13 9 14 32 9 26 47 t 16 =2.45, P=0.026 28 14 9 11 31 7 16 34 t 14 =0.48, NS 21 18±3 42±6 17±2 38±3 26±2 Femle did not return fter chicks htched. Mle wited nine dys before bndoning the chicks.

170 Otley et l.: Breeding biology of the Gentoo Penguin in the Flklnd Islnds Overll breeding production, bsed on the number of chicks just before fledging, ws 1.3 chicks/pir. DISCUSSION Across its geogrphic rnge, the Gentoo Penguin exhibits vrition in timing of breeding, forging trip lengths during incubtion nd brood periods, nd individul nd colony-wide breeding success, with birds within the sme ocenic system shring similr ptterns. Gentoo Penguins breeding on Mrion, Crozet nd Kerguelen in the southern Indin Ocen commence breeding during winter months nd forge for men periods of three dys during incubtion nd 1.3 dys during brooding (Tble 4). No. of ctive nests/chicks 1600 1400 1200 1000 800 600 400 200 0 No. nests No. chicks 02/11 17/11 02/12 17/12 01/01 16/01 31/01 15/02 02/03 17/03 Dte Fig. 1. Totl numbers of breeding pirs nd chicks t Volunteer Bech t five-dy intervls, indicted by the number of ctive nests with eggs nd chicks during November December nd the number of chicks in Jnury Mrch, 2001/02. Breeding success of Gentoo Penguins in the southern Indin Ocen is low, t fewer thn 0.5 chicks/pir, which leds to replcement clutches being lid in spring months (Tble 4). In contrst, t South Georgi, South Atlntic Ocen, the South Shetlnd Islnds nd the Antrctic Peninsul, nd t Mcqurie Islnd in the southern Pcific Ocen, breeding is initited only in spring months. Gentoo Penguins in colonies t those loclities undertke shorter forging trips during both incubtion nd brooding, with men length of fewer thn 1.4 dys during incubtion nd 0.5 dys during brooding. On verge, pirs cn successfully rise between 0.9 nd 1.2 chicks ech yer (Tble 4). At Volunteer Bech, the men htching dte for the first egg in 14 nests ws erly December, similr to other studied colonies in the South Atlntic Ocen/Antrctic Peninsul region. The overll breeding success of 1.3 chicks/pir reported in the present study ws higher thn the 10-yer men t Volunteer Bech of 0.86 chicks/pir (Pütz et l. 2001), level tht ws somewht lower thn the levels recorded elsewhere in the South Atlntic Ocen/Antrctic Peninsul region (Tble 4). Minimum mximum forging trip lengths t Volunteer Bech during incubtion nd brooding (2.0 3.0 dys nd 0.7 1.8 dys respectively) were longer thn the typicl trips undertken by Gentoo Penguins elsewhere in the South Atlntic Ocen/Antrctic Peninsul region nd more similr to the trip lengths reported for birds in the southern Indin Ocen (Tble 4). Long forging trips re usully ssocited with low breeding success t colonies in the southern Indin Ocen (Bost & Jouventin 1990), but this cse does not pper to hve held t Volunteer Bech during 2001/02. For exmple, the men mss of six chicks in this study t the end of the brood period (3.2 kg) ws higher thn the nnul mens (1.6 2.7 kg) over three sesons t nerby South Georgi (Willims 1995). Adult body condition is one fctor tht TABLE 4 Comprison of the timing of breeding, men forging length, breeding success nd body mss of mle nd femle Gentoo Penguins in the southern Indin, Pcific nd South Atlntic Ocens nd the Antrctic Peninsul region Ocen Loclity Ltitude Length Smple Breeding Men forging Men Men body of study size initited length (d) breeding mss (kg) Incubtion Brood success Mle Femle (chicks/pir) Indin Crozet 1 46 4 sesons 455 June 2.8 1.2 0.48 6.7 Mrion 1 46 1 seson June 0.43 Kerguelen 1 49 1 seson June 3.1 1.4 0.60 5.4 Pcific Mcqurie 2 54 1 seson 15 October 0.5 0.98 5.7 South Flklnds 3 51 1 seson 14 October 2.0 3.0 0.7 1.8 0.87 7.0 6.6 Atlntic Antrctic South 54 3 sesons 30 200 October 1.4 0.5 0.90 5.9 5.1 Georgi 4 South 61 2 sesons 885 October 0.5 0.5 1.17 Shetlnds 5 Antrctic 64 1 seson 26 October 1.12 5.8 5.0 Peninsul 6 Body mss of unsexed birds from Willims (1995). Sources: 1. Bost & Jouventin 1990; 2. Robertson 1986, Robinson & Hindell 1996; 3. Clusen & Pütz 2002, this study; 4. Willims 1995, Croxll et l. 1999; 5. Trivelpiece et l. 1987; 6. Renner et l. 1998, Quintn & Cirelli 2000.

Otley et l.: Breeding biology of the Gentoo Penguin in the Flklnd Islnds 171 contributes to the bility to withstnd long periods fsting onshore during incubtion nd brooding (Bost & Jouventin 1991). The men incubtion mss of nine mles nd seven femles t Volunteer Bech ws lmost 1 kg hevier thn the men incubtion mss of both sexes t colonies in South Georgi nd the Antrctic Peninsul nd lso when compred to unsexed dults t vrious stges of breeding t Crozet, Kerguelen nd Mcqurie Islnds (Tble 4). Htching success in colonies cross the rnge of the Gentoo Penguin is usully round 60% 70%, becuse of bndonment resulting primrily from delyed relief (Willims 1980, Trivelpiece et l. 1987, Bost & Jouventin 1990, 1991, Willims 1995). Despite comprtively long incubtion shifts t Volunteer Bech, no nests were bndoned, resulting in high htching success. The bility to withstnd extended fsting periods ws lso shown by one study bird t Volunteer Bech tht bndoned brooded chicks only fter nine dys. Birds t Crozet bndoned chicks fter s little s five dys (Bost & Jouventin 1991). Our results indicte tht the breeding biology of Gentoo Penguins t the Flklnd Islnds represents mixture of the ptterns displyed by birds from the South Atlntic Ocen/Antrctic Peninsul region nd the southern Indin Ocen. Without t-se dt such s diet, forging distnce nd prey vilbility in combintion with the unknown impcts of egg collecting nd tourism t Volunteer Bech it is difficult to interpret more fully the breeding ptterns exhibited. Two of the study pirs lid only one norml-sized egg, but tht egg is unlikely to hve been replcement egg replcement eggs re often smller (Bost nd Clobert 1992). Study clutches were not thought to be complete replcement clutches fter egg collection becuse intervls of up to 25 dys usully occur between filure nd re-lying (Bost nd Clobert 1992). Given the species plstic breeding phenology (Willims 1990), multi-nnul study with lrger smple sizes is required to fully understnd the breeding biology nd forging ecology of the Gentoo Penguin in the Flklnd Islnds. ACKNOWLEDGEMENTS We thnk Smith Brothers for llowing ccess to the site, G. nd J. Smith for sfety communictions, T. McKeown nd R. Hrris for ssistnce with fieldwork nd N. Huin for vluble dvice. Trnsport nd logisticl ssistnce ws provided by D. Broughton, T. Smith, S. Hlford, P. Wtts, D. Eynon nd B. Stewrt. The project ws supported by the Rotterdm Zoo nd the Mount Plesnt Complex Chrity. REFERENCES BARBOSA, A., MORENO, J., POTTI, J. & MERINO, S. 1997. Breeding group size, nest position nd breeding success in the Chinstrp Penguin. Polr Biology 18: 410 414. BOST, C.A. & CLOBERT, J. 1992. Gentoo Penguin Pygoscelis ppu: fctors ffecting the process of lying replcement clutch. Act Ecologic 13: 593 605. BOST, C.A. & JOUVENTIN, P. 1991. 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