994 SHORT COMMUNICATIONS

The Condor 99:994-997 0 The Cooper Ornithological Society 1997

CHANGES IN KING BREEDING CYCLE IN RESPONSE TO FOOD AVAILABILITY’

OLOFOLSSON Department of Zoology, Villavagen 9, Uppsala University, S-752 36 Uppsala, Sweden and British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 OET, UK, e-mail: oloJ:[email protected] ANDERSBRODIN Department of Zoology, Stockholm University, S-106 91 Stockholm, Sweden

Abstract. From 1991 to 1996 we investigatedhow breeding cycle, including prebreedingmolt, takes 13- the breeding cycle of Ring PenguinsAptenodytes pa- 16 months to complete successfully(Weimerskirch et tagonicus, in a small colony at South Georgia, was al. 1992, Jouventin and Lagarde 1995, Olsson 1996). affected by variation in food availability between The single chick overwinters in the colony and is rare- years. During the first (1992) and third (1996) of the ly or never fed during this time. The parents resume three successful cycles studied, food was plentiful, provisioning the next spring (September-October) and whereas food availability was lower during the second the chick becomes independent some months later. cycle (1994). We found (1) the duration of breeding Hence, a complete breeding and molt cycle, from one was longer (455 days) in 1994 comparedto 1992 (437 egg-laying to the next, involves two summers.Despite days) and 1996 (438 days), (2) fewer made late this, the parents then molt and may start a new breed- breeding attempts in 1994 (38%) than in 1992 (88%) ing attempt the second of these two summers, that is and 1996 (70%), and (3) those birds that made late the same summer as the previous chick fledged, but attempts laid their egg later in 1994 (mean 16 March) this time in February or March insteadof in November compared to 1992 (19 February) and 1996 (21 Feb- or December, which was the start time of the previous ruary). We conclude that the breeding timetable breeding. Thus, they often try to breed each summer changedin responseboth to the reducedavailability of (annually) and there are typically two temporally sep- food in 1994 and to the subsequentimproved condi- arated peaks of breeding activities in a Ring Penguin tions in 1996. This suggeststhat annualversus biennial colony, depending on the outcome of the previous at- breeding in Ring is dependenton the avail- tempt (for details, see Olsson 1996). ability of food and the condition of the birds. The general pattern of the Ring Penguin breeding cycle is similar in various locations, including South Key words: , King Penguin, life-history Georgia (Stonehouse 1960, Olsson 1996), Crozet Ar- trade-08 prey abundance, seabird, state-dependent chipelago (Barrat 1976, Weimerskirch et al. 1992, Jou- decision. ventin and Lagarde 1995), Heard Island (van den Hoff 1993), and Marion Island (du Plessis et al. 1994, van For most birds, the period from laying eggs to fledging Heezik et al. 1994). Nevertheless, there are some dif- chicks is completed within one calendar year and ferencesin the timing of the late breeding attemptsand breeding takes place annually at the same time each the proportion of birds undertakingthem. It is probable year. Depending upon abiotic factors, food availability that such differences depend on food availability (Wei- often varies seasonally,and it is adaptive for birds to merskirch et al. 1992, Olsson 1996). time energy-demanding events, like breeding and We investigated three breeding cycles which were molting, to periods of high availability of food (Lack temporally separatedby years of total failure. In the 1968, Perrins 1970). Birds with long development of first and last cycle, the availability of food was good, offspring may have breeding cycles that exceed one whereasit was lower during the intermediatecycle. We year. In these , the typical pattern is breeding compared (1) the duration of the breeding cycle, (2) every two years in synchrony with seasons,with one the proportion of successfulbirds preparing for (molt, exception: the Ring PenguinAptenodytes patagonicus. courtship) or starting (egg laid) late breeding, and (3) Ring Penguins, breeding on sub-Antarctic islands, the timing of egg-laying in late attempts.Compared to feed pelagically in polar waters on myctophid fish the first and last cycle, we expected to find significant which are more available in summer than in winter changesin all three variablesin the secondcycle when (Cherel et al. 1993, Olsson and North, in press). The food availability was lower. METHODS 1Received 7 November 1996. Accepted 10 June We studied a Ring Penguin colony (-200 individuals) 1997. at Husvik (54”ll’S 36”4O’W), South Georgia each SHORT COMMUNICATIONS 995

0 1992(n=49) 611994(n=66) n 1996(n=20)

(x1=32) (n=24) 1992 1994 lo96 FIGURE 1. Mean ? SD duration of successful breeding cycles of King Penguins, i.e., from one egg- laying to the next. FIGURE 2. Percentageof King Penguinsinvolved in preparations for late breeding attempts (prebreeding molt and courtship) and accomplishing late breeding austral summer from 199011991 to 1995/1996. The attempts (egg laid), after having raised a chick to in- main study period each season was from October or dependenceearlier the same summer. November to March or April. For convenience,we will refer to the austral summersby the their last calendar year, e.g., the summer of 1991/1992 is 1992, etc. Moreover, the breeding cycle that startedin the austral cycle lasted on average 455 days (65 weeks) and was summer of 199011991 and ended in the 1991/1992 18 and 17 days longer than the cycles of 1992 and summer, will be referred to as the breeding cycle of 1996, respectively (Fig. 1). 1992, becausethat is the summer of fledging. There were no significant differences between the Almost all birds in the colony were individually three breeding cycles in the proportionof birds starting identified by using metal flipper bands and passiveim- a late prebreedingmolt (xz2 = 0.8, P = 0.66) and late planted electronic transponder tags (TIRIS). Tran- courtship (x *2 = 4.2, P = 0.12), after having raised a spondersserved as backup marking for potential band chick to independence(Fig. 2). There was, however, a loss which, however, did not occur. We could read significant difference between the three cycles in the more than 95% of the bands daily with a telescopeor proportion of birds that had a late egg. (xz2 = 13.8, P binoculars. = 0.001) (Fig. 2). Although the difference was signif- Two observations supported the assumption that icant only for egg-laying, Figure 2 shows that the pat- food availability was poor in the summer of 1994 rel- tern also was the same for molt and courtship: high ative to the other summersof this study. First, the du- proportions of birds were involved in 1992 and in ration of foraging trips was longer in 1994 (Olsson 1996, whereas lower proportions were involved in 1995), which suggeststhat birds were less able to find 1994. food. As a consequence,> 60% of pairs failed during The mean (2 SD) datesof egg-laying for birds mak- incubationin 1994 comparedto < 10% of failure dur- ing late breeding attemptswere similar in 1992 and in ing the other summers. Second, a larger proportion of 1996; 19 February + 11.3 days (n = 26) and 21 Feb- otoliths from the main prey fish was eroded in 1994 ruary ? 9.1 days (n = 8) respectively. In 1994, how- (Olsson and North, in press), suggestingthat prey were ever, the mean date was later, 16 March ? 18.9 days caught further away from the colony and/or less fre- (n = 14). This difference in mean laying date of late quently. Moreover, the nutritional condition in general attemptsbetween years was significant (F2.45= 17.2, P for higher predators around South Georgia was very < 0.001). poor in 1994 (Boyd et al. 1995, Brierley and Watkins DISCUSSION 1996). REASONSFOR BREEDINGFAILURE IN I993 AND 1995 RESULTS The reason why no pair was successfulin 1993 was The successfulbreeding cycles of 1992, 1994, and likely some combination of: (1) a large proportion of 1996 resulted in 32, 33, and 10 fledging chicks, re- the birds in the colony were successfulin their previ- spectively. In the intervening summers, 1993 and ous attempt and hence were late breeders,which made 1995, no chicks fledged. them less likely to breed successfully(Weimerskirch Measured from one egg-laying to the next, including et al. 1992, Jouventin and Lagarde 1995, Olsson molting, there was a significant difference in duration 1996); (2) among the early breeders, which normally of breeding between the three successfulbreeding cy- are more likely to be successful,there was probably cles (ANOVA, F2,64= 19.5, P < 0.001). The 1994 an unusuallyhigh proportion of low quality birds (see 996 SHORT COMMUNICATIONS

Olsson 1996), which are more likely to fail; (3) some A combination of three features makes the King condition(s) such as weather and/or prey abundance Penguin breeding cycle unique: it exceeds one year, may have been particularly unfavorable during the molt takes place before breeding, and they make a late winter of 1993; survival of chicks also was low in the breeding attempt after the first chick has fledged in the larger Fortuna Bay colony approximately 15 km away secondsummer. In all wild populations,over-wintering (as it was in the winter of 1995). The reason for no of the chick seems to be obligatory (Williams 1995). chicks fledging in 1995 was the extremely poor for- The reason for this may be that the alternative, the aging conditionsin the summer of 1994. All pairs lay- chick becoming independent at the end of the first ing eggs failed before the winter and, hence, no chick summer,may result in reduced chick survival because was alive that could fledge in 199.5. the inexperienced chick has to learn to feed for itself It seems paradoxical that the poor summer of 1994 at a time of vear when food availabilitv is declining had no effect on prefledging survival of the over-win- rapidly. The late breeding attemptsof successfulbirds: tered yearling chicks that hatched in 1993, whereas on the other hand, seem to be optional and flexible. those chicks that hatched in 1994 all died before the We suggestits occurrence and timing can be greatly winter. However, compared to over-wintered yearling influenced by the availability of food. However, it re- chicks fledging in 1992, those fledging in 1994 mains unclear why late attemptsare made at all, con- weighed less prior to departure,fledged at a later date, sidering that very few such attempts are successful and the survival and recruitmentrates were lower (Ols- (Weimerskirch et al. 1992, van Heezik et al, 1994, Ols- son, in press b). son 1996). The answer may be that breeding incurs A consequenceof the complete failure in 1993 and only small extra costs compared to the potential ad- 1995 was that each of the three successfulbreeding vantagesof successif availability of food is unusually cvcles (1992. 1994. and 1996) were seuaratedbv a good (Olsson 1996). year of ‘failure. This temporal separation&alsoallowed us to compare seasonswhen all birds in the colony We thank the British Antarctic Survey (BAS) and were early breeders, and therefore data were not con- the Swedish Antarctic Research Program for logistic founded by different proportionsof birds with presum- support. Financial support was obtained from the ably different prospects of breeding success,due to Swedish Natural Science ResearchCouncil, BAS, and late breeding, in the three years compared. Stiftelsen Olle Engquist Byggmlstare. For assistance in the field we are grateful to l? Anker-Nilssen, J. Bon- EFFECTS OF POOR FOOD AVAILABILITY nedahl, E. Soglo, C. Day, H. MacAlister, A. Morton, Compared to the 1992 breeding cycle, when availabil- and J. Pailthorp. ity of food was good, the 1994 breeding cycle was longer, fewer birds made late attempts, and those that LITERATURE CITED laid eggs did so later. Moreover, in 1996, when the availability of food was good again, the duration of BARRAT,A. 1976. Quelques aspectsde la biologie et the breeding cycle, the proportion of birds undertaking de l’ecologie du manchot royal ( pa- late attempts, and timing of late egg-laying all were tugonicus) des iles Crozet. Corn. Nat. Fr. Res. Ant. similar to 1992. Hence, our predictionswere supported 40:9-51. and we conclude that the main features of the King BOYD,I. L., J. I? CROXALL,N. J. LUNN, AND K. REID. Penguin breeding cycle are influenced by the avail- 1995. Population demography of Antarctic fur ability of food. seals: the costs of reproduction and implications We believe that the differences in 1994 are related for life-histories. J. Anim. Ecol. 64:505-518. to the fact that all activities which involved foraging BRIERLEY,A. S., AND J. L. WATKINS. 1996. Acoustic took longer time in 1994. For example, the chickswere targets at South Georgia and the South Orkney fed less often and therefore required longer time to Islands during a seasonof scarcity.Mar. Ecol. fledge, which delayed the late breeding attempt of their Prog. Ser. 138:51-61. parents.Also, fattening trips to sea to acquire reserves CHEREL,Y., C. VERDON,AND V. RIDOUX. 1993. Sea- in preparationfor prebreedingmolt and courtshiptook sonal importance of oceanic myctophids in King longer time and causedfurther delay (Olsson 1995). Penguin diet at Crozet Island. Polar Biol. 13:355- The fact that more birds refrained from late breeding 357. attemptsin the poor year of 1994 suggeststhat this is DU PLESSIS,C. J., Y. M. VAN HEEZIK,AND I? J. SEDDON. a decision which is influenced by the prospect of ob- 1994. Timing of King Penguin breeding at Mar- taining sufficient food for breeding, without increasing ion Island. Emu 94:216-219. energv exuenditure too much. At least four variables JOU~ENTIN,P, AND E LAGARDE.1995. Evolutionary may be involved in the decision of whether to under- ecology of the King Penguin Aptenodytes pat&- take a late breeding attempt or not: the date of fledging gonicus: the self-regulation of the breeding cycle, of the previous chick, prey availability, the general p. 80-95. In P Dann, I. Norman, and I? Reilly condition of the , suchas fat reserves,and previous reds.], The penguins. Surrey Beatty & Sons, Sid- experience. Consequently, annual versus biennial ney. breeding may be a decision which is dependenton the LACK, D. 1968. Ecological adaptationsfor breeding condition or “state” of the birds (see McNamara and in birds. Methuen, London. Houston 1996). Similarly, state-dependentdecisions MCNAMARA,J. M., ANDA. I. HOUSTON.1996. State- also may influence clutch abandonmentin King Pen- dependentlife histories. Nature 380:215-221. guins (Olsson, in press a). OLSSON,0. 1995. Timing and body-reserve adjust- SHORT COMMUNICATIONS 997

ments in King Penguin reproduction.Ph.D. diss., patagonica of South Georgia. I. Breeding behav- Uppsala University, Uppsala, Sweden. iour and development. Sci. Rep. Falkl. 1~1.Dep. OLSON, 0. 1996. Seasonaleffects of timing and re- Sur. 23:1-81. production in the King Penguin: a unique breed- VAN DEN HOFF,J., R. J. KIRKWOOD,AND I? B. COPLEY. ing cycle. J. Avian Biol. 27:7-14. 1993. Aspects of the breeding cycle of King Pen- OLSON, 0. In press a. Clutch abandonment:a state- guins Aptenodytespatanonicus at Heard Island. dependent decision in King Penguins. J. Avian Mar. O&thol.~21:49-55‘: Biol. VAN HEEZIK,Y. M., P J. SEDDON.J. COOPER,AND A. L. PLUS. 1994. Interrelationship between breed- OLSSON, 0. In press b. Effects of food availability on ing frequency, timing and outcome in King Pen- fledging condition and post-fledging survival in guin Aptenodytespatagonicus: are King Penguins King Penguin chicks. Polar Biol. biennial breeders?Ibis 136:279-284. OLSSON, O., AND A. W. NORTH.In press. Diet of the WEIMERSKIRCH,H., J. C. STAHL, AND P JOUVENTIN. King Penguin Aptenodytespatagonicus during 1992. The breeding bioloev and nooulation dv- three summersat South Georgia. Ibis. namics of King PegguinsAptenodytes patagonica PERRINS, C. M. 1970. The timing of birds’ breeding on the . Ibis 134:107-l 17. seasons.Ibis 112:242-255. WILLIAMS,‘I D. 1995. The penguins. Oxford Univ. STONEHOUSE,B. 1960. The King PenguinAptenodytes Press, Oxford.

The Condor Y9:997-1001 D The Cooper Omithologlcal Society 1997

THE LENGTH OF INCUBATION IN RELATION TO NEST INITIATION DATE AND CLUTCH SIZE IN DABBLING DUCKS’

CLIFFL. FELDHEIM~ Departmentof Wildlife, Humboldt State University,Arcata, CA 95221

Abstract. There are a growing number of studies The length of incubation in waterfowl may have im- which suggestthat variable incubationperiods may be portant consequencesfor individual fitness, including the norm for waterfowl, and that this variation may be length of exposure to predators (Arnold et al. 1987) correlated with other life-history traits. I examined and parental energetics (Thompson and Raveling variation in length of incubationin relation to nest ini- 1987). Whereas many studies have focused on inter- tiation date and clutch size in five speciesof dabbling specific variation in incubation periods (reviewed by ducks during 1995 and 1996. I also conducteda ma- Afton and Paulus 1992), relatively few studies have nipulative experiment to directly assessthe relation- addressedintraspecific variation. In general, waterfowl ship between clutch size and incubation period in incubationperiods have been reportedas single values. Blue-winged Teal (Anus discors).The length of incu- However, there are a growing number of studieswhich bation declined seasonallyfor all species and in both suggest that variable incubation periods may be the years. After controlling for nest initiation date, incu- norm for waterfowl (Aldrich and Raveling 1983, Hepp bation periods were positively correlated with clutch et al. 1990, Arnold 1993). In addition, this variation size in only one speciesduring one of two years. En- may be correlated with other life-history traits. Hepp larged clutches were incubated two days longer than control or reducedclutches, although reduced and con- et al. (1990) showed that incubationperiods in Wood trol clutcheshad similar incubationlengths. These re- Ducks (Aix sponsa) was positively correlated with sults suggest that clutch size explains only a small clutch size (i.e., dump nests), and the length of incu- amount of the total variation in incubationlength, and bation declined with nest initiation date in one of three the cost of incubation may operate with other factors years. Arnold (1993) found a similar seasonaldecline to help limit clutch size in Blue-winged Teal. in incubationperiod for artificially-incubateddabbling duck eggs (Anus spp.). Key words: Blue-winged Teal, clutch size, Gad- In this study, I examined the effect of nest initiation wall, incubationperiod, Mallard, nest initiation date, date and clutch size on the length of incubationin five Northern Pintail, Northern Shoveler. speciesof uplandnesting dabbling ducks:Blue-winged Teal (Anus discors),Mallards (A. phztyrhynchos),Gad- ’ ’ Received 9 January 1997. Accepted 20 May 1997. walls (A. streperu), Northern Pintails (A. acuta), and 2 Current Address: Sacramento National Wildlife Northern Shovelers (A. clypeata). In addition, I con- Refuge, 752 County Road 99W, Willows, CA 95988. ducted a clutch size manipulation experiment to di-