Stabilizing selection on body mass in the sociable weaver Philetairus socius

The survival of small birds is often believed to increase with increasing body mass, despite some evidence that body mass is usually maintained below the physiological maximum and that there are costs associated with high body mass, such as increased energetic expenditure and predation risk. In this study, we used an eight–year dataset to investigate survival in relation to body mass in a wild population of sociable weavers (Philetairus socius), a savannah–dwelling passerine bird. We present evidence for strong stabilizing selection on body mass, verifying the prediction that body mass probably results from a trade–off between the risks of starvation at low mass and predation at high mass.

[1]  R. Griffiths,et al.  A DNA test to sex most birds , 1998, Molecular ecology.

[2]  A. Armstrong,et al.  Ecological and life-history correlates of cooperative breeding in South African birds , 1995, Oecologia.

[3]  H. Akaike,et al.  Information Theory and an Extension of the Maximum Likelihood Principle , 1973 .

[4]  Charles R. Brown,et al.  Coloniality in the Cliff Swallow: The Effect of Group Size on Social Behavior , 1996 .

[5]  David R. Anderson,et al.  Modeling Survival and Testing Biological Hypotheses Using Marked Animals: A Unified Approach with Case Studies , 1992 .

[6]  G. Maclean.  THE SOCIABLE WEAVER, PART 5: FOOD, FEEDING AND GENERAL BEHAVIOUR , 1973 .

[7]  A. Gosler,et al.  Fat reserves and perceived predation risk in the great tit, Parus major , 2001, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[8]  Christopher M. Perrins,et al.  Population fluctuations and clutch size in the Great tit , 1965 .

[9]  David R. Anderson,et al.  Model selection and multimodel inference : a practical information-theoretic approach , 2003 .

[10]  N. Metcalfe,et al.  Diurnal variation in flight performance and hence potential predation risk in small birds , 1995, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[11]  David R. Anderson,et al.  Model selection and inference : a practical information-theoretic approach , 2000 .

[12]  Marsden Rm.  Coloniality in the sociable weaver Philetairus socius. , 1999 .

[13]  T. Fransson,et al.  Impaired predator evasion in fat blackcaps (Sylvia atricapilla) , 1996, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[14]  Kenneth H. Pollock,et al.  Design and Analysis Methods for Fish Survival Experiments Based on Release-Recapture. , 1988 .

[15]  A. Houston,et al.  The value of fat reserves and the tradeoff between starvation and predation , 1990, Acta biotheoretica.

[16]  M. Brown,et al.  INTENSE NATURAL SELECTION ON BODY SIZE AND WING AND TAIL ASYMMETRY IN CLIFF SWALLOWS DURING SEVERE WEATHER , 1998, Evolution; international journal of organic evolution.

[17]  G. Maclean.  THE SOCIABLE WEAVER, PART 3: BREEDING BIOLOGY AND MOULT , 1973 .

[18]  A. Møller,et al.  Condition, disease and immune defence , 1998 .

[19]  K. Burnham,et al.  Program MARK: survival estimation from populations of marked animals , 1999 .

[20]  I. Cuthill,et al.  The ecological costs of avian fat storage. , 1993, Philosophical transactions of the Royal Society of London. Series B, Biological sciences.

[21]  I. Cuthill,et al.  Managing time and energy , 1997 .

[22]  S. L. Lima.  PREDATION RISK AND UNPREDICTABLE FEEDING CONDITIONS: DETERMINANTS OF BODY MASS IN BIRDS' , 1986 .

[23]  J. Greenwood,et al.  Predation risk and the cost of being fat , 1995, Nature.

[24]  Burt,et al.  Natural selection in the wild. , 2000, Trends in ecology & evolution.

[25]  P. Grant,et al.  Oscillating selection on Darwin's finches , 1987, Nature.

[26]  L. Lens,et al.  Stabilizing selection on blue tit fledgling mass in the presence of sparrowhawks , 1998, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[27]  J. Krebs,et al.  Behavioural Ecology: An Evolutionary Approach , 1978 .

[28]  G. Maclean.  THE SOCIABLE WEAVER, PART 4: PREDATORS, PARASITES AND SYMBIONTS , 1973 .

[29]  David R. Anderson,et al.  Practical Use of the Information-Theoretic Approach , 1998 .