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 sec...
Main Author: | |
---|---|
Format: | Doctoral or Postdoctoral Thesis |
Language: | English |
Published: |
University of Cape Town
1980
|
Subjects: | |
Online Access: | http://hdl.handle.net/11427/21425 https://open.uct.ac.za/bitstream/11427/21425/1/thesis_sci_1980_williams_anthony_john.pdf |
id |
ftunivcapetownir:oai:localhost:11427/21425 |
---|---|
record_format |
openpolar |
spelling |
ftunivcapetownir:oai:localhost:11427/21425 2023-05-15T16:08:23+02:00 The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism Williams, Anthony John 1980 application/pdf http://hdl.handle.net/11427/21425 https://open.uct.ac.za/bitstream/11427/21425/1/thesis_sci_1980_williams_anthony_john.pdf eng eng University of Cape Town Faculty of Science Department of Biological Sciences http://hdl.handle.net/11427/21425 https://open.uct.ac.za/bitstream/11427/21425/1/thesis_sci_1980_williams_anthony_john.pdf Zoology Doctoral Thesis Doctoral PhD 1980 ftunivcapetownir 2022-09-13T05:50:34Z 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 ... Doctoral or Postdoctoral Thesis Eudyptes chrysolophus Marion Island Rockhopper penguin University of Cape Town: OpenUCT Austral |
institution |
Open Polar |
collection |
University of Cape Town: OpenUCT |
op_collection_id |
ftunivcapetownir |
language |
English |
topic |
Zoology |
spellingShingle |
Zoology Williams, Anthony John The breeding biology of Eudyptes penguins with particular reference to egg-size dimorphism |
topic_facet |
Zoology |
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 ... |
format |
Doctoral or Postdoctoral Thesis |
author |
Williams, Anthony John |
author_facet |
Williams, Anthony John |
author_sort |
Williams, Anthony John |
title |
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_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_sort |
breeding biology of eudyptes penguins with particular reference to egg-size dimorphism |
publisher |
University of Cape Town |
publishDate |
1980 |
url |
http://hdl.handle.net/11427/21425 https://open.uct.ac.za/bitstream/11427/21425/1/thesis_sci_1980_williams_anthony_john.pdf |
geographic |
Austral |
geographic_facet |
Austral |
genre |
Eudyptes chrysolophus Marion Island Rockhopper penguin |
genre_facet |
Eudyptes chrysolophus Marion Island Rockhopper penguin |
op_relation |
http://hdl.handle.net/11427/21425 https://open.uct.ac.za/bitstream/11427/21425/1/thesis_sci_1980_williams_anthony_john.pdf |
_version_ |
1766404440644911104 |