{"id":{"repo_id":"cape-town","oai_identifier":"oai:open.uct.ac.za:11427/21425"},"canonical_url":"https://search.dev.ndltd.org/etd/cape-town/oai:open.uct.ac.za:11427/21425","repository":{"repo_id":"cape-town","name":"University of Cape Town","base_url":"https://open.uct.ac.za/oai/request"},"display":{"title":"The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism","abstract":"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.","abstract_html":"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.","abstract_has_math":false,"creators":["Williams, Anthony John"],"institution":"Department of Biological Sciences","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":1980,"date_issued":"1980","date_published":"1980","updated_at":"2026-07-22T22:23:01Z","subjects":[],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/11427/21425","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Williams, Anthony John"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2016-08-22T12:25:41Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2016-08-22T12:25:41Z"]},{"key":"dc:date.issued","label":"Date","values":["1980"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["Department of Biological Sciences"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Cape Town"]},{"key":"dc:type","label":"Dc Type","values":["Doctoral Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["PhD"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/11427/21425"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["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."]},{"key":"dc:title","label":"Title","values":["The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism"]}]}],"canonical_facts":{"dc:creator":["Williams, Anthony John"],"dc:date.accessioned":["2016-08-22T12:25:41Z"],"dc:date.available":["2016-08-22T12:25:41Z"],"dc:date.issued":["1980"],"dc:description.abstract":["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."],"dc:identifier.uri":["http://hdl.handle.net/11427/21425"],"dc:language.iso":["eng"],"dc:publisher.department":["Department of Biological Sciences"],"dc:publisher.institution":["University of Cape Town"],"dc:title":["The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism"],"dc:type":["Doctoral Thesis"],"dc:type.qualificationlevel":["Doctoral"],"dc:type.qualificationname":["PhD"]},"updated_at":"2026-07-22T22:23:01Z"}