The Adaptive Significances of Intraspecific Trends of Variation in Wing Length and Body Size Among Bird Species

Hamilton, T. H.

doi:10.2307/2406079

Cited by 89 publications

(67 citation statements)

References 8 publications

(10 reference statements)

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“…Anyway, such possible morphological changes might affect flight performance and manoeuvrability (see Hamilton 1961), but were an insufficient explanation for the observed age differences in diet, because the effect remained after excluding all 1 year old males from the analysis. The same result was obtained with both modelling approaches (GLMM and resampling procedure).…”

Section: Discussionmentioning

confidence: 99%

Age-dependent diet choice in an avian top predator

2005

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Age-dependent breeding performance is arguably one of the best-documented phenomena in ornithology. The existence of age-related trends has major implications for life-history theory, but the proximate reasons for these patterns remain poorly understood. It has been proposed that poor breeding performance of young individuals might reflect lack of foraging skills. We investigated this possibility in a medium-sized, powerful raptor-the northern goshawk Accipiter gentilis. Male goshawks are responsible for providing their females and their offspring with food. We hypothesized that young males may generally show poor breeding performance or even delay breeding, because they lack the experience to hunt efficiently-especially, their principal avian prey, the feral pigeon Columba livia. Our study exploited a rare 'natural experiment', the expansion phase of an urban population, where intraspecific interference was negligible and many young males bred successfully. This enabled us to examine the improvement of foraging skills in a larger sample of young individuals, and in more controlled conditions than usually possible. Using data from individually identified male breeders, we show that, consistent with our hypothesis, the proportion of pigeons in the diet increased significantly with male age, for at least the first three years of life. Other studies have shown a parallel increase in productivity, and a positive effect of a pigeon-rich diet on brood size and nestling condition, stressing the potential fitness relevance of this prey species for goshawks. Our results suggest a causal link between patterns of age-dependence in foraging ecology and reproductive performance. Furthermore, our study is, to our knowledge, the first demonstration that prey choice of breeders, which might reflect individual hunting skills, is age-dependent in a raptor.

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Section: Discussionmentioning

confidence: 99%

Age-dependent diet choice in an avian top predator

2005

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“…Causal explanations for the underlying basis of Bergmann's Rule have traditionally invoked the adaptive significance of body size in connection with temperature regulation or conservation of metabolic water (Hamilton, 1961;Mayr, 1963;Brown & Lee, 1969;Power, 1969;James, 1970). An alternative hypothesis is that geographic patterns of size variation primarily reflect selection for fasting endurance during episodic periods of food scarcity in seasonal environments (Boyce, 1979;Lindstedt & Boyce, 1985;Millar & Hickling, 1990).…”

Section: Geographic Variation In Body Sizementioning

confidence: 99%

“…Because the evaporative surface area/volume ratio is inversely proportional to body size, this hypothesis predicts that larger size is advantageous in hot arid environments, and smaller size is advantageous in hot humid environments. Intraspecific variation in birds of the genus Vireo provides supporting evidence, as birds are smallest in the humid lowland tropics of Central America, and largest in the hot, arid deserts of northern Mexico (Hamilton, 1958(Hamilton, , 1961. Likewise, in the 12 species of North American birds studied by James (1970), body size (as indexed by wing length) was smallest in the hot, humid southeast and exhibited a progressive increase across a westward gradient of increasing aridity and a northward gradient of decreasing temperature.…”

Section: Introductionmentioning

confidence: 96%

“…In hot aridlands and tropical environments, geographic variation in the size of small-bodied homeotherms may often reflect an adaptive response to the challenges of conserving metabolic water and/or maximizing heat dissipation (Hamilton, 1958(Hamilton, , 1961Brown & Lee, 1969Power, 1969James, 1970). Because the evaporative surface area/volume ratio is inversely proportional to body size, this hypothesis predicts that larger size is advantageous in hot arid environments, and smaller size is advantageous in hot humid environments.…”

Section: Introductionmentioning

confidence: 99%

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Clinal variation in body size and sexual dimorphism in an Indian fruit bat, Cynopterus sphinx (Chiroptera: Pteropodidae)

Storz

Balasingh²,

Bhat

et al. 2001

Biological Journal of the Linnean Society

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Geographic variation in body size and sexual dimorphism of the short‐nosed fruit bat (Cynopterus sphinx) was investigated in peninsular India. Bats were sampled at 12 localities along a 1200 km latitudinal transect that paralleled the eastern flanks of the Western Ghats. The geographic pattern of variation in external morphology of C. sphinx conforms to the predictions of Bergmann's Rule, as indicated by a steep, monotonic cline of increasing body size from south to north. This study represents one of the first conclusively documented examples of Bergmann's Rule in a tropical mammal and confirms that latitudinal clines in body size are not exclusively restricted to temperate zone homeotherms. Body size was indexed by a multivariate axis derived from principal components analysis of linear measurements that summarize body and wing dimensions. Additionally, length of forearm was used as a univariate index of structural size to examine geographic variation in a more inclusive sample of bats across the latitudinal transect. Multivariate and univariate size metrics were strongly and positively correlated with body mass, and exhibited highly concordant patterns of clinal variation. Stepwise multiple regression on climatological variables revealed that increasing size of male and female C. sphinx was associated with decreasing minimum temperature, increasing relative humidity, and increasing seasonality. Although patterns of geographic size variation were highly concordant between the sexes, C. sphinx also exhibited a latitudinal cline in the magnitude and direction of sexual size dimorphism. The size differential reversed direction across the latitudinal gradient, as males averaged larger in the north, and females averaged larger in the south. The degree of female‐biased size dimorphism across the transect was negatively correlated with body size of both sexes. Canonical discriminant analysis revealed that male‐ and female‐biased size dimorphism were based on contrasting sets of external characters. Available data on geographic variation in the degree of polygyny in C. sphinx suggests that sexual selection on male size may play a role in determining the geographic pattern of sexual size dimorphism.

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“…Previous studies have demonstrated a positive relationship between body size and latitude in both birds and mammals (Ashton 2002a;Meiri and Dayan 2003;Gardner et al 2009;Olson et al 2009). However, limited information is available on altitudinal variation in body size (Hamilton 1961;Blackburn and Ruggiero 2001;Chown and Klok 2003;Wilson et al 2010;Gutiérrez-Pinto et al 2014). Although latitudinal and altitudinal gradients show similar temperature trends (Ashton and Feldman 2003), some climate factors, such as solar radiation, air pressure (AP) (or oxygen concentration), are more strongly associated with variation in altitude than latitude (Liao et al 2006;Körner 2007, also see Additional file 1: Table S1).…”

Section: Introductionmentioning

confidence: 99%

The role of climate factors in geographic variation in body mass and wing length in a passerine bird

Sun

Song

et al. 2017

Avian Res

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Background: Geographic variation in body size is assumed to reflect adaptation to local environmental conditions. Although Bergmann's rule is usually sufficient to explain such variation in homeotherms, some exceptions have been documented. The relationship between altitude, latitude and body size, has been well documented for some vertebrate taxa during the past decades. However, relatively little information is available on the effects of climate variables on body size in birds. Methods:We collected the data of 267 adult Eurasian Tree Sparrow (Passer montanus) specimens sampled at 48 localities in China's mainland, and further investigated the relationships between two response variables, body mass and wing length, as well as a suit of explanatory variables, i.e. altitude, latitude, mean annual temperature (MAT), annual precipitation (PRC), annual sunshine hours (SUN), average annual wind speed (WS), air pressure (AP) and relative humidity (RH). Results:Our study showed that (1) although the sexes did not differ significantly in body mass, males had longer wings than females; (2) body mass and wing length were positively correlated with altitude but not with latitude; (3) body mass and wing length were negatively correlated with AP and RH, but not significantly correlated with WS. Body mass was positively correlated with SUN and inversely correlated with MAT. Wing length was not correlated with MAT in either sex, but was positively correlated with SUN and negatively correlated with PRC in male sparrows; (4) variation in body mass could be best explained by AP and SUN, whereas variation in wing length could be explained by RH and AP in both sexes. In addition, variation in male sparrows can be explained by SUN, WS and PRC but not in females. Conclusions:Two different proxies of body size, body mass and wing length, correlated with same geographic factors and different climate factors. These differences may reflect selection for heat conservation in the case of body mass, and for efficient flight in the case of wing length.

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The Adaptive Significances of Intraspecific Trends of Variation in Wing Length and Body Size Among Bird Species

Cited by 89 publications

References 8 publications

Age-dependent diet choice in an avian top predator

Age-dependent diet choice in an avian top predator

Clinal variation in body size and sexual dimorphism in an Indian fruit bat, Cynopterus sphinx (Chiroptera: Pteropodidae)

The role of climate factors in geographic variation in body mass and wing length in a passerine bird

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