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The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism
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 (...
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| Format: | Thesis |
| Language: | English |
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Department of Biological Sciences
2016
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| _version_ | 1867613229352484864 |
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| access_status_str | Open Access |
| author | Williams, Anthony John |
| author_browse | Williams, Anthony John |
| author_facet | Williams, Anthony John |
| author_sort | Williams, Anthony John |
| collection | Thesis |
| description | 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. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/21425 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:32:47.627Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| publisher | Department of Biological Sciences |
| publisherStr | Department of Biological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/21425 The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism Williams, Anthony John Zoology 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. 2016-08-22T12:25:41Z 2016-08-22T12:25:41Z 1980 Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/21425 eng application/pdf Department of Biological Sciences Faculty of Science University of Cape Town |
| spellingShingle | Zoology Williams, Anthony John The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism |
| thesis_degree_str | Doctoral |
| title | The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism |
| title_full | The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism |
| title_fullStr | The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism |
| title_full_unstemmed | The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism |
| title_short | The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism |
| title_sort | breeding biology of eudyptes penguins with particular reference to egg size dimorphism |
| topic | Zoology |
| url | http://hdl.handle.net/11427/21425 |
| work_keys_str_mv | AT williamsanthonyjohn thebreedingbiologyofeudyptespenguinswithparticularreferencetoeggsizedimorphism AT williamsanthonyjohn breedingbiologyofeudyptespenguinswithparticularreferencetoeggsizedimorphism |