The Ostrich Communal Nesting System (Monographs in Behavior and Ecology)

206 Pages·2016·65.812 MB·English

by  Brian C.R. Bertram

The Ostrich
Communal Nesting
System
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MONOGRAPHS IN BEHAVIOR
AND ECOLOGY
Edited by John R. Krebs and
Tim Clutton-Brock
Five New World Primates: A Study in Comparative
Ecology, by John Terborgh
Reproductive Decisions: An Economic Analysis of
Gelada Baboon Social Strategies, by R. /. M. Dunbar
Honeybee Ecology: A Study of Adaptation in Social Life,
by Thomas D. Seeley
Foraging Theory, by David W. Stephens
and John R. Krebs
Helping and Communal Breeding in Birds.
Ecology and Evolution, by Jerram L. Brown
Dynamic Modeling in Behavioral Ecology, by Marc Mangel
and Colin W. Clark
The Biology of the Naked Mole-Rat, edited by Paul W.
Sharmen, Jennifer U. M. Jarvis and Richard D. Alexander
The Evolution of Parental Care, by T. H. Clutton-Brock
The Ostrich Communal Nesting System,
by Brian C. R. Bertram
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The Ostrich
Communal Nesting
System
BRIAN C. R. BERTRAM
Princeton University Press
Princeton New Jersey
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Copyright © 1992 by Princeton University Press
Published by Princeton University Press, 41 William Street,
Princeton, New Jersey 08540
All Rights Reserved
Library of Congress Cataloging-in-Publication Data
Bertram, Brian, C. R , 1944-
The ostrich communal nesting system / Brian C.R.
Bertram,
p. cm. — (Monographs in behavior and ecology)
includes bibliographical references and index.
ISBN 0-691-08785-7
1. Ostriches-Behavior. 2. Sexual behavior in animals.
3. Ostriches-nests. 4 Social behavior in animals. I. Title
II. Series.
QL696 S9B47 1992 92-22198
598'.510456-dc20 CIP
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Contents
Preface vii
1
The Ostrich 1
2
Methods 19
3
The Population 33
4
The Breeding System 49
5
Ecological Aspects 71
6
Strategies Adopted by Major
Females 102
7
Major and Minor Female Strategies 124
8
Male Strategies 138
9
Discussion: The Evolution and
Maintenance of the Communal
Nesting System 159
References 188
Subject Index 193
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Preface
Surprisingly, this field study of ostriches grew directly out of my earlier
research on lions in the Serengeti National Park in Tanzania. It was a
chance encounter, while searching for lions, with an ostrich nest
containing just recognizably different eggs, that prompted a much more
thorough look: it appeared that contrary to what natural selection usually
dictates, a female ostrich seemed to be doing all of another female's work
for her. At that time, in 1973, there was a new and rapidly growing interest
in cooperation and apparent altruism in animal social systems, and in how
such behaviour could evolve through natural selection. Lion research was
revealing the ways in which cooperation and altruism in that species could
be selected for. In many respects, ostrich eggs promised to be more
amenable subjects for comparative study than elusive mobile nocturnal
carnivores.
Both the ostrich and its eggs have an improbable impressiveness about
them. The close observer is struck by the size and the height of the eye, the
power of the legs and the softness of the barbless feathers. The creamy
white round egg, the equivalent of some 25 ordinary chickens' eggs, has
a mystique which matches its food value. And as this study showed, the
ostrich communal nesting system is complex, intriguing and adapted to
the birds' difficult environment.
As with any study, it was not carried out in isolation, but depended on
a great deal of help from others. I am indebted to three organizations for
financial support. The study was conducted while I held a Senior Research
Fellowship in the Research Centre at King's College, Cambridge from
1976 to 1979. Fortunately, the long university vacation was apparently
designed to coincide with the ostrich breeding season in Kenya. Field work
expenses were covered by research grants from the Royal Society and the
Natural Environment Research Council - which means the UK taxpayer.
I am grateful to the Office of the President and the Wildlife Conser­
vation and Management Department of the Government of Kenya for
permission to carry out research work in Tsavo West National Park, and
to the then Senior Park Wardens Ted Goss and Bill Woodley and their
staff for friendly local assistance and advice. I was glad of association with
the Zoology Department of Nairobi University and with the Department
of Ornithology of the National Museums of Kenya.
The study benefited greatly from the ingenuity of Emrys Williams who
produced excellent timing devices to operate cheap time-lapse cameras
(Section 2.3), and of William Bertram who devised temperature-recording
ostrich eggs (Section 2.4).
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VIII • PREFACE
Continuous off-track driving in rough terrain can be hard on vehicles,
so I am particularly grateful for the generosity of Rosemary and Alasdair
Macdonald and of William Bertram for the loan of theirs.
Several people helped during the fieldwork in Tsavo, particularly
Debbie Snelson and Anna Baird (now McCann) for the last field season;
a good many others helped with observations and in other ways during
shorter periods. Rosemary and Alasdair Macdonald and Ann and Mike
Norton-Griffiths kindly provided invaluable bases in Mombasa and
Nairobi.
A brief study visit to South Africa to look at ostrich farming practice
was made successful through the kind help of Roy Siegfried, Alan and
Valerie Burger, and several ostrich farmers at Oudtshoorn.
I am grateful for discussion and comments at various stages to many
people, but particularly Debbie Snelson, Anna Baird, Tim Clutton-Brock,
Dan Rubenstein, Steve Albon and Richard Wrangham. I am grateful too
for the forbearance shown by many people over the years in not asking too
often how the book was coming along. For the typing of the general result,
I should like to thank Hazel Clarke, Mary Gillie, Elspeth Chaplin, Jacquie
Cook, Alison Byard and Jennifer Owen. David Bygott's sketches have
helped to bring the birds to life.
But the person who has contributed by far the most to the study has
been Kate Bertram. That contribution has included three seasons of being
a first-class joint ostrich observer and superb camp organizer, many hours
of analysis of unexciting time-lapse photographs and general tolerance
with her spouse throughout.
To all the above, I can only reiterate my grateful thanks.
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The Ostrich
Running
1.1 The Bird Itself
The ostrich is well known to be the world's largest living bird. An adult
male stands 2.1-2.7m high (Cramp and Simmons, 1980). Females are
generally a bit smaller. Information on measured weights of these birds in
the wild is characteristically scarce; a small sample (n = 13) from Kenya
averaged 111 kg, ranging from 86 to 145 kg (A.V. Milewski, pers. comm.).
Their size alone would render ostriches incapable of flight. Instead, they
are adapted to a walking and running way of life. The very long bare legs
carry the large bird economically (Fedak and Seeherman, 1979) and when
necessary at up to 60-70 km/h (Brown et αι., 1982), with strides of up to
8.5 m (Smit, 1963). The reduction in the number of toes from the normal
five to only two in the ostrich is probably another adaptation for fast
running. The large inner toe (originally the third) and occasionally the
smaller outer toe (originally the fourth) carry a powerful nail.
Ostriches' wings are considerably reduced. The feathers are without
barbs, which contributes to their loose, soft appearance. The primary
feathers are developed as large plumes, used in display and sought after by
human beings. Much of the body is devoid of feathers, particularly the
long neck, the whole of the legs and patches on the underside of the body.
The adult male's body plumage is jet black, with the exception of white
plumage on its wings and tail. The female's feathers are of a fairly uniform
earthy pale brown-grey colour.
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