SHORT COMMUNICATIONS 1111 TheCondor96:1111-1113 Q The CooperOmithological Society 1994 DIVING DEPTHS OF WHITE-CHINNED PETRELS ’ N. Hum British Antarctic Survey,Natural EnvironmentResearch Council, High Cross,Madingley Road, Cambridge,CB3 OET U.K. Key words: White-chinned Petrel; diving depth; Burger and Wilson (1988) Prince and Jones (1992) feeding behavior;Procellaria aequinoctialis. and Prince et al. (1994) that is 10 cm lengths of clear PVC tubing of 1 mm internal diameter, heat-sealed at For many seabirds, the ability to submerge to capture one end, with soluble indicator powder introduced into prey is a key adaptation for their foraging behavior. the other end. The gauge was attached with adhesive Studies of diving in seabirds have typically featured tape to a metal leg band. Breeding burrows were checked species known to be virtually dependent on long, often twice daily and birds recaptured on subsequent visits deep, dives for their livelihood, e.g., penguins (re- to feed their chick. Birds were caught using a box, of viewed in Croxall et al. 1993) alcids (reviewed in Bur- dimensions 20 cm x 20 cm (aperture) x 50 cm (length) ger 199 1), cormorants (Wilson and Wilson 1988, Crox- with a trapdoor at one end, inserted into the mouth of all et al. 199 1, Wanless et al. 199 1). As far as the size a burrow. (A trapdoor alone was readily circumvented of the birds has permitted, these studies have pro- by the bird.) Because White-chinned Petrels typically ceeded from collecting data on maximum depth ofdive make lengthy foraging trips, averaging 34 days (Hall via multiple maximum depths to continuous records 1987) gauge deployments ranged from l-12 days. To of diving depth against time and recently, in the larger minimize disturbance to a species known to be sen- penguins, with simultaneous collection of velocity and/ sitive (Hall 1987) only one gauge deployment was made or locational data (Kooyman et al. 1992, Ancel et al. per individual. 1992). Gauges were recovered from 11 birds and the length Although some members of the Procellariiformes of the tube still covered with indicator powder was and of other families of the Pelecaniformes (e.g., Su- measured to the nearest 0.5 mm. Maximum depth at- lidae) have long been known as proficient divers (Ku- tained was calculated by the equation: roda 1954, Ashmole 1971, Brown et al. 1978) only anecdotal information on the depths they attain has been available until very recently. The use of light- weight capillary gauges (Burger and Wilson 1988) has where d,,,,, is maximum depth (m), L, is the initial created opportunities to obtain reliable quantitative length (mm) of undissolved indicator and Ld the length data on the maximum depth reached by a wide variety (mm) on recovery (Burger and Wilson 1988). of seabirds, particularly penguins and alcids (Burger 1991) but also Cape Gaune& Sula capensis(.&%I& RESULTS and Walter 1993). South Georaia Divina Petrels Pele- The durations of gauge deployment and depths at- canoidesgeorgick (Prince and Jones 1<92), and four tained by each bird are given in Table 1. There was no species of albatross Diomedeidae (Prince et al. 1994). significant difference in mean maximum depth be- With the exception of the highly specialized Peleca- tween the sexes (t = 1.46, P = 0.28) nor in relation to noididae, the Procellaridae (petrels and shearwaters) the size of the bird (whether expressed as mass, or as are the best adapted of the Procellariiformes for diving. mass corrected for body size using bill or wing mea- Species in this family may dive as much as 20 m deep surements). However, the maximum depth recorded (Skim 1979). This paper reports the first systematic was positively related to gauge deployment duration quantitative data on diving depths for any species of (depth = 2.58~+ 0.624 duration, r2 = 0.47, P = 10.05), petrel. although this relationship was no longer significant if the deepest dive was excluded. METHODS Fieldwork was carried out at Bird Island, South Geor- DISCUSSION gia (54“OOS,’ 38”02W)’ between 7-28 March 1993, ap- The results indicate that White-chinned Petrels reach proximately half-way through the chick-rearing period. depths of 13 m. Such depths are not dissimilar to those Seventeen capillary gauges were attached to adult birds reported for Pu#inus shearwaters of 40-60°h the mass that had returned to feed their chicks. Most birds were of White-chinned Petrels. Thus Skira (1979) recorded sexed (by comparison of bill measurements between Short-tailed Shearwaters P. tenuirostrisreaching lO- the two partners, males being the larger (N. Huin, un- 12 m and possibly 20 m, Brown et al. (198 1) reported publ. data). The gauges were similar to those used by Sooty Shearwaters P. griseusattaining 10 m and Wood (1993) recorded Flesh-footed and Fluttering shearwa- ters P. carneipesand P. gavia reaching 5 m and 2-3 I Received 15 April 1994. Accepted 27 July 1994. m, respectively. 1112 SHORT COMMUNICATIONS TABLE 1. Maximum diving depths and gauge de- chinned Petrels. The only study of the species’ diet, at ployment durations of White-chinned Petrels at South South Georgia in 1985/1986 (Croxall et al., in press), Georgia. showed that Antarctic krill Euphausia superba, lan- temfishes Myctophidae and oceanic squid (mainly the ommastrephid Martialia hyadesi) were the main prey. hdPbgr' Mass Maximum All these frequently occur in large swarms or shoalsat Bird SW (9) WYS) depth(m) or near the sea surface (Croxall et al., in press) and 088 1,170 1 2.8 would probably be very suitabletargets for pursuit and 089 F 1,080 5 5.4 capture on relatively short and shallow dives. 090 F 1,400 12 12.8 I thank P. A. Prince for encouraaementand advice 091 M 1,150 5 8.3 in this study, J. Cooper for help& the field, J. R. 092 M 1,200 2 3.3 Ashford and M. J. Whitehouse for their unpublished 096 M 1,300 7 3.0 observations, J. P. Croxall for help in preparing the 097 F 1,330 6 9.1 manuscript,J. Leland for typing it and two anonymous 098 1,330 8 4.9 reviewers for helpful comments. 099 1,400 10 7.2 100 1,380 3 4.9 LITERATURE CITED 103 F 1,230 5 6.6 ADAMS,N. J., AM) C. B. WALTER. 1993. Maximum diving depths of Cape Gannets. Condor 95:734- It is not easy to assessthe accuracyof the results in 736. the presentstudy. Burgerand Wilson (1988) found that ANCEL, A., G. L. KOO~MAN, P. J. PONGAN~S,J.-P. gaugessubjected to simulated plunge-diving overesti- GENDNER,J. LIGNON,X. MESTRE,N. Hum, P. H. mated denths bv 39% and 9W on submeraenceto 5 m THORSON,P. ROBISSON,AND Y. LE MAHO. 1992. and 10 m, respectively. However, most observations Foraging behaviour of Emperor Penguinsas a re- on feeding by White-chinned Petrels indicate that they sourcedetector in winter and summer. Nature 360: rarely plunge-dive (and then from heights of only 0.3- 336-337. 0.5 m (M. J. Whitehouse,pers. comm.), mainly making ASHMOLE,N. P. 1971. Seahird ecology and the ma- surface dives (Harper et al. 1985) so overestimation tine environment, p. 224-286. In D. S. Famer, J. of dive depth is unlikely from this source. Wanless et R. King, and K. C. Parkes teds.], Avian biology, al. (199 1) suggestedthat gaugeson European Shags Vol. 1. Academic Press, New York. Phalacrocorax aristotelis not recovered within 24 hr BROWN,R.G.B., W.R.P. BOURNE,AND T. R. WAHL. -gave less nlausible (overestimated) results. In White- 1978. Diving- by_ shearwaters.Condor 80: 123-l 25. chinned Petrels, there was an increase in maximum BROWN, R.G.B., S. P. BARKER,D. E GASKIN,AND M. recorded dive depth with deployment duration, but R. SANDEMAN. 1981. The foods of Great and this was small and could well simply reflect the greater Sooty ShearwatersPufinus gravis and P. griseus likelihood of recordingdeeper dives the longerthe gauge in eastern Canadian waters. Ibis 123:19-30. is in operation. Overall, even if overestimating dive BURGER,A. E. 1991. Maximum diving depths and depth by lo%, my data indicate that diving White- underwaterforaging in alcids and penguins.In W. chinned Petrels regularly attain 5 m and can reach 12 A. Montevecchi and A. J. Gaston [eds.], Studies m. of high latitude seabirds. 1. Behavioural energetic White-chinned Petrels observed making wing-pro- and oceanographicaspects of seabirdfeeding ecol- pelled surface dives had dive durations that averaged ogy. Can. Wildl. Serv., Occas. Pap. No. 68:9-15. 2.4 set (SD 2.0, range 0.4-6.3 set, n = 14) (M. J. BURGER,A. E., AND R. P. WILSON. 1988. Capillary- Whitehouse, pers. comm.). Another observerreported tube depth gaugesfor diving animals: an assess- similar dives lasting at least 5 set (J. R. Ashford, pers. ment of their accuracyand applicability. J. Field comm.). These records probably substantially under- Omithol. 59:345-354. estimate the breath-hold capacity of White-chinned CROXALL, J. P., Y. NAITO,A. KATO, P. ROTHERY,AND Petrels but if they can travel at 2 m set-l (as typically D. R. B~GGS. 1991. Diving patterns and per- recorded for wing-propelled penguins(Kooyman et ai. formance in the Antarctic Blue-eyed Shag Phal- 1992) and alcids (Swennen and Duiven 1991) under- acrocorax atriceps. J. Zool. (Lond.) 225: 177-199. water), then on a 6 set dive they could reach 6 m, CROXW, J. P., D. R. B~GGS, A. KATO, Y. NAITO, Y. which is the averagedepth recordedby the birds in the WATANUKI,AM) T.