Fil: Casaux, Ricardo Jorge. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina. Universidad Nacional de la Patagonia; Argentin

Casaux, Ricardo Jorge

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109Beak deformation in sub-Antarctic and Antarctic birds is rare, or atleast has been rarely reported (see Pütz & Plötz 1991,Splettstoesser & Todd 1998, Voisin et al. 2002). In Antarctica suchan anomaly has been observed only in chicks of EmperorAptenodytes forsteri (Pütz & Plötz 1991, Splettstoesser & Todd1998) and Gentoo Pygoscelis papua (R. Casaux, pers. obs.)penguins. Given that, for adult specimens, this phenomenon has notbeen reported in the Antarctic literature, such an anomaly is likelyto reduce survival. Pütz & Plötz (1991) described beakdeformations in two moulting Emperor Penguin chicks and,although both individuals left the breeding locality without evidentdetrimental effects, they suggested that the birds would be unableto forage.As part of a study on the breeding biology of the AntarcticCormorant or Shag Phalacrocorax [atriceps] bransfieldensis, Iobserved beak deformation in a recently hatched chick and madeobservations on the chick’s growth and survival. The study wascarried out at Harmony Point (62°17′S, 59°13′W), Nelson Island,South Shetland Islands, Antarctica, during the 2000/01 breedingseason.At the laying date, assessed to an accuracy of one day, the egg ofthe chick under study was weighed with a Pesola spring balance(accuracy: 1 g) and then numbered. Subsequently, the nest wasvisited every two days. The chick was weighed on hatching(accuracy: 1 g) and then every five days (accuracy: 1–25 g). Thesame methodology was followed with the remaining chicks at thecolony. The increase in mass of the chick under study and of thosehealthy chicks used for comparison of growth rate were fittedaccording to the Gompertz equation, which best fit the increase inmass in Antarctic Cormorant chicks at Harmony Point in previousseasons (Casaux 1998). The equation is expressed asM = A x e (–B × e(–K × t) ),where M represents the body mass in grams, A is the asymptoticbody mass, K is the growth rate constant, B is a constant and t isthe age of the chick in days (Ricklefs 1968).The beak deformation consisted of the lateral deviation of theanterior portion of the upper mandible (Fig. 1). Despite theanomaly, the feeding behaviour of the chick under study wassimilar to that observed in the other chicks in the colony.BEAK DEFORMATION IN AN ANTARCTIC CORMORANTPHALACROCORAX [ATRICEPS] BRANSFIELDENSIS CHICKR. CASAUXInstituto Antártico Argentino, Cerrito 1248, 1010 Buenos Aires, Argentina(pipocasaux@infovia.com.ar)Current address: Laboratorio de Ecología Acuática, Universidad Nacional de la Patagonia, Sarmiento 849, 9200 Esquel, Chubut, ArgentinaReceived 8 January 2003, accepted 21 September 2003Fig. 1. (A) Lateral and (B) dorsal view of the maxillarydeformation observed in an Antarctic Cormorant chick at HarmonyPoint, South Shetland Islands, Antarctica.Fig. 2. Comparison of the increase in mass between (A) anAntarctic Cormorant chick with a deformed beak and (B–E) fournormal chicks from single-chick broods at Harmony Point, SouthShetland Islands, Antarctica.Marine Ornithology 32: 109-110 (2004)The deformed chick hatched on 18 December 2000 from the firstegg of a clutch of three, after 33 days of incubation. The meanincubation period observed at the colony for the first egg of three-egg clutches or for one-egg clutches was 32.4 days [standarddeviation (s.d.): 1.21 days; range: 30–35 days; mode: 33 days; n= 37]. The next day, the only other chick at the nest hatched (fromthe third egg of the clutch and without beak deformation), but itdied four days later. Thus, from an age of six days, the deformedchick was alone in the nest. (The second egg of the clutch was notviable.) The chick’s mass at hatching was 45 g, representing 76.3%of the fresh egg mass of 59 g. The mean mass of eggs at laying andchicks at hatching were 58.5 g (s.d.: 4.63 g; range: 49–71 g; n = 148) and 44.3 g (s.d.: 6.63 g; range: 33–58 g; n = 74),respectively.The increase in mass observed in the deformed chick and in thoseused for comparison (Fig. 2) was well fitted by the Gompertzequation (coefficient of correlation: 0.98 to 0.99). The increase inmass of the deformed chick was slower than that of healthy birdsin single-chick broods. At an age of 38 days, the chick reached apeak mass of 1780 g (roughly 59% of the body mass of fledgingchicks at the colony). The deformed chick died at an age of 44days (beginning of the moulting period), weighing 1550 g, aftertwo days of severe weather conditions during part of which it was,for the first time, not brooded. Non-surviving chicks at the colonydied at a mean age of 14.7 days (s.d.: 12.3 days; range: 1–54 days;mode: 4 days; n = 36), whereas fledging commenced at 75–85days of age.Several causes—such as congenital defects, deficiency diseases,parasitic infections, injuries, pollution and abnormal feeding of thenestling—have been proposed to explain beak deformation(Gylstorff & Grimm 1987). Given that the chick hatched with adeformed beak and that egg mass, incubation period and mass athatching were close to the mean values observed at the colony, onlycongenital defects or injuries during hatching might be consideredto be the cause of the anomaly reported here.The deformed chick grew more slowly than did the remainingchicks in single-chick broods at the colony. A delay in increase inmass was evident during the first 10 days of life (Fig. 2). It isknown that, in this period of the life cycle, Antarctic Cormorantchicks are fed with small pieces of fish (Casaux et al. 1998). Aschicks grow older, larger pieces and even whole fish are offered byparents. Thus, the delay in the increase in mass during the first daysof life might be associated with mechanical limitations in handlingsmall food items.The deformed chick died at an age of 44 days, markedly older thanmost of the non-surviving chicks in the colony. Just before itsdeath, the chick had recently started to moult; it weighed52.7%–74.8% of the mass of normal chicks from single-chickbroods of the same age. Whereas Antarctic Cormorant chicksremain permanently brooded up to an age of 20 days (Casaux1998), the deformed chick was brooded up to the age of 42 days.During days 42 and 43, severe weather conditions affected thecolony, and the chick remained unbrooded most of the time.Although almost all parents remained away from the colony duringmost of those two bad-weather days, only one other chick died atthe colony during that period. The most likely explanation for the death of the deformed chick is that it was unable to ingestsufficient food for successful growth, feather development andthermoregulation.ACKNOWLEDGEMENTSI thank A. Baroni who helped with the field activities and E. Barrera–Oro who commented on the manuscript.REFERENCESCASAUX, R. 1998. Biología reproductiva y ecología alimentariadel Cormorán Antártico Phalacrocorax bransfieldensis (Aves,Phalacrocoracidae) en las Islas Shetland del Sur, Antártida. PhDThesis. La Plata, Argentina: University of La Plata.CASAUX, R., BARRERA–ORO, E., FAVERO, M. & SILVA, P.1998. New correction factors for the quantification of fishrepresented in pellets of the Imperial Cormorant Phalacrocoraxatriceps. Marine Ornithology 26: 35–39.GYLSTORFF, I. & GRIMM, F. 1987. Vogelkrankheiten. Stuttgart:Verlag Eugen Ulmer.PÜTZ, K. & PLÖTZ, J. 1991. Beak deformations in EmperorPenguin Aptenodytes forsteri chicks. Polar Record 27: 367.RICKLEFS, R. 1968. Patterns of growth in birds. Ibis 110:419–451.SPLETTSTOESSER, J. & TODD, F. 1998. Further observations ofbeak deformations in Emperor Penguin Aptenodytes forsterichicks. Marine Ornithology 26: 79.VOISIN, J.-F., MOUGIN, J.-L., SEGONZAC, M. &ROPERT–COUDERT, Y. 2002. Colour aberrations and physicaldeformities in the King Penguin Aptenodytes patagonicus at theCrozet Islands. Marine Ornithology 30: 1–4.110 Casaux: Beak deformation in an Antarctic Cormorant chickMarine Ornithology 32: 109-110 (2004)

Beak deformation in an Antarctic Cormorant Phalacrocorax [atriceps] bransfieldensis chick

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Beak deformation in an Antarctic Cormorant Phalacrocorax [atriceps] bransfieldensis chick

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