The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism

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dc.contributor.authorWilliams, Anthony Johnen_ZA
dc.date.accessioned2016-08-22T12:25:41Z
dc.date.available2016-08-22T12:25:41Z
dc.date.issued1980en_ZA
dc.description.abstractThe breeding biology of Macaroni Penguins Eudyptes chrysolophus and of Rockhopper Penguins E. chrysocome was studied at Marion Island (46°54'8, 37°45'E) in the austral summers of 1974-75 and 1976-77. The clutch comprises two eggs, the first-laid (A-) egg being markedly smaller than the second-laid (B-) egg. Components of B-eggs are heavier than the same components of A-eggs. Incubation begins after the B-egg is laid. Incubation of B-eggs lasts 34 and 36 days in Rockhopper and Macaroni Penguins respectively. Parents treat the larger egg preferentially. In Macaroni Penguins, less than 1% of all A-eggs hatch and 54% of all A-eggs are lost before the B-egg in the same clutch is laid. In Rockhopper Penguins, both eggs are retained until one hatches at 30% of all nests, but both eggs hatch at only 12% of all nests. The B-egg hatches before the A-egg. Hatchling weight and the growth of chicks for the first 35 days after hatching are correlated with egg weight. B-egg chicks grow significantly faster than A-egg chicks and are heavier within 24 h of "fledging". Chicks of both species are fed at intervals of 36-92 hours and receive about 30 meals during the 70-day chick-rearing period. Except in exceptional circumstances, Macaroni Penguins rear no A-egg chicks. When two Rockhopper Penguin chicks hatch from dimorphic eggs, one dies of starvation within 12 days but in experiments chicks hatched from two eggs of similar size co-existed for up to 57 days. Chicks are raised successfully from 3% of all A-eggs laid by Rockhopper Penguins, and from 34% and 43% of all B-eggs laid by Rockhopper and Macaroni Penguins respectively. Only one chick can be reared from each clutch. Egg-size dimorphism predetermines the offspring most likely to survive. Eudyptes penguins may forage 100 km from the colony when feeding chicks. However, the ancestral Eudyptes was probably an inshore-feeder laying two eggs of similar size and capable of raising two chicks. Egg-size dimorphism has probably developed through major enlargement of the B-egg, and possibly arose in the course of the transition from inshore to offshore foraging.en_ZA
dc.identifier.apacitationWilliams, A. J. (1980). <i>The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/21425en_ZA
dc.identifier.chicagocitationWilliams, Anthony John. <i>"The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 1980. http://hdl.handle.net/11427/21425en_ZA
dc.identifier.citationWilliams, A. 1980. The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Williams, Anthony John AB - The breeding biology of Macaroni Penguins Eudyptes chrysolophus and of Rockhopper Penguins E. chrysocome was studied at Marion Island (46°54'8, 37°45'E) in the austral summers of 1974-75 and 1976-77. The clutch comprises two eggs, the first-laid (A-) egg being markedly smaller than the second-laid (B-) egg. Components of B-eggs are heavier than the same components of A-eggs. Incubation begins after the B-egg is laid. Incubation of B-eggs lasts 34 and 36 days in Rockhopper and Macaroni Penguins respectively. Parents treat the larger egg preferentially. In Macaroni Penguins, less than 1% of all A-eggs hatch and 54% of all A-eggs are lost before the B-egg in the same clutch is laid. In Rockhopper Penguins, both eggs are retained until one hatches at 30% of all nests, but both eggs hatch at only 12% of all nests. The B-egg hatches before the A-egg. Hatchling weight and the growth of chicks for the first 35 days after hatching are correlated with egg weight. B-egg chicks grow significantly faster than A-egg chicks and are heavier within 24 h of "fledging". Chicks of both species are fed at intervals of 36-92 hours and receive about 30 meals during the 70-day chick-rearing period. Except in exceptional circumstances, Macaroni Penguins rear no A-egg chicks. When two Rockhopper Penguin chicks hatch from dimorphic eggs, one dies of starvation within 12 days but in experiments chicks hatched from two eggs of similar size co-existed for up to 57 days. Chicks are raised successfully from 3% of all A-eggs laid by Rockhopper Penguins, and from 34% and 43% of all B-eggs laid by Rockhopper and Macaroni Penguins respectively. Only one chick can be reared from each clutch. Egg-size dimorphism predetermines the offspring most likely to survive. Eudyptes penguins may forage 100 km from the colony when feeding chicks. However, the ancestral Eudyptes was probably an inshore-feeder laying two eggs of similar size and capable of raising two chicks. Egg-size dimorphism has probably developed through major enlargement of the B-egg, and possibly arose in the course of the transition from inshore to offshore foraging. DA - 1980 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1980 T1 - The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism TI - The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism UR - http://hdl.handle.net/11427/21425 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/21425
dc.identifier.vancouvercitationWilliams AJ. The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 1980 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/21425en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Biological Sciencesen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherZoologyen_ZA
dc.titleThe breeding biology of Eudyptes penguins with particular reference to egg-size dimorphismen_ZA
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhDen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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