Breeding density, not life history, predicts interpopulation differences in territorial aggression in a passerine bird

Yoon, Jongmin; Sillett, T. Scott; Morrison, Scott; Ghalambor, Cameron K.

doi:10.1016/j.anbehav.2012.05.024

Cited by 46 publications

(43 citation statements)

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“…The intensity of conspecific territorial aggression in a population is also shaped by conspecific density [5,6]; environments with high conspecific density are thought to favour elevated territoriality [7]. The elevated territorial aggression in urban male song sparrows leads us to predict that the urban areas considered here would have a higher density of birds than the surrounding rural areas, which we tested by comparing point counts of song sparrows in the two habitat types.…”

Section: Introductionmentioning

confidence: 99%

“…Territorial aggression is a crucial behaviour that is found throughout the animal kingdom and is used to defend limited resources, such as breeding territories, mates or food [5,6]. Although aggression has been the focus of considerable research, few studies have investigated the factors underlying interpopulation variation in territorial aggression [7]. In this study, we tested whether urbanization-related differences in territorial aggression were individually consistent within a breeding period and whether the hormone testosterone and/or conspecific density, two factors associated with territoriality, differed across habitat types.…”

Section: Introductionmentioning

confidence: 99%

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Agonistic urban birds: elevated territorial aggression of urban song sparrows is individually consistent within a breeding period

Davies¹,

Sewall²

2016

Biol. Lett.

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Urban birds often more vigorously defend their territories during simulated intrusions than do their rural counterparts, but the factors responsible remain unclear. To address this issue, we investigated whether the disparity in territorial aggression of urban and rural male song sparrows, Melospiza melodia, is individually consistent within a breeding period. Additionally, to better understand the physiological and ecological factors underlying this behavioural difference, we examined whether territoriality was associated with plasma testosterone, a hormone that contributes to elevated aggression in vertebrates, and/or conspecific density, a factor often positively related to aggression. The urbanization-related difference in territoriality was individually consistent within a breeding period. However, the elevated territorial aggression of urban birds was not associated with plasma testosterone and, counter to our predictions, conspecific density was lower in urban compared with rural areas. We suggest that other aspects of testosterone signalling and features of the socio-ecological environment, such as the availability of breeding sites, may underlie increased territorial aggression in urban birds.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Agonistic urban birds: elevated territorial aggression of urban song sparrows is individually consistent within a breeding period

Davies¹,

Sewall²

2016

Biol. Lett.

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“…At the nest level, greater variation in territory quality and food delivery rates could increase variation between nests. Birds in California breed at a high density on an island, respond strongly to simulated territorial intrusions, and maintain higher testosterone levels during the nestling period than birds in Alaska (Horton et al 2010, Yoon et al 2012), suggesting stronger competition for high quality territories in that population. Therefore, we predicted the amount of variation between nests would be higher in California.…”

Section: Variation In Orange‐crowned Warbler Growth Trajectoriesmentioning

confidence: 99%

Advantages of nonlinear mixed models for fitting avian growth curves

Sofaer¹,

Chapman²,

Sillett³

et al. 2013

Journal of Avian Biology

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Our understanding of avian growth rates can benefit from the use of two statistical approaches that explicitly model the sources of intraspecific variation. First, random effects can evaluate whether there are consistent differences between individuals and groups of siblings within a population, and also account for any lack of statistical independence among data points. Second, nonlinear fixed‐effect functions can be extended to test specific biological hypotheses of interest, such as for differences between groups or populations. We illustrate the advantages of these methods by using nonlinear mixed models to study variation in the growth trajectories of nestling orange‐crowned warblers Oreothylpis celata. Specifically, we quantify the sources of variation within populations, analyze the effects of asynchronous hatching, and test for a difference in the growth rates of populations in Alaska and California, which are at the northern and southern limits of the species’ breeding distribution. We found that growth rates did not consistently vary between nests and individuals within populations and were not affected by asynchronous hatching, but were higher in Alaska than in California. Our extensions of traditional methods allowed us to accurately quantify this difference between populations, which is consistent with life history theory but has rarely been demonstrated in previous comparisons of intraspecific passerine populations. The methods we present can be applied to any taxonomic group and adjusted to fit any nonlinear function, and we provide code and implementation advice to facilitate the use of this analytical framework in future studies.

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“…Therefore, it has been proposed that aggression is most beneficial at moderate densities (Grant, ). Experiments exploring the density‐dependent advantages of aggression have demonstrated an increase in the frequency and intensity of aggressive interactions or displays as the foraging patch size decreases (Johnson, Grant, & Giraldeau, ) or density increases (Yoon, Sillett, Morrison, & Ghalambor, ).…”

Section: Introductionmentioning

confidence: 99%

Experimental evidence that density mediates negative frequency‐dependent selection on aggression

Kilgour

McAdam

Betini

et al. 2018

Journal of Animal Ecology

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Aggression can be beneficial in competitive environments if aggressive individuals are more likely to access resources than non-aggressive individuals. However, variation in aggressive behaviour persists within populations, suggesting that high levels of aggression might not always be favoured. The goal of this study was to experimentally assess the effects of population density and phenotypic frequency on selection on aggression in a competitive environment. We compared survival of two strains of Drosophila melanogaster that differ in aggression across three density treatments and five frequency treatments (single strain groups, equal numbers of each strain and strains mixed at 3:1 and 1:3 ratios) during a period of limited resources. While there was no difference in survival across single-strain treatments, survival was strongly density dependent, with declining survival as density increased. Furthermore, at medium and high densities, there was evidence of negative frequency-dependent selection, where rare strains experienced greater survival than common strains. However, there was no evidence of negative frequency-dependent selection at low density. Our results indicate that the benefits of aggression during periods of limited resources can depend on the interaction between the phenotypic composition of populations and population density, both of which are mechanisms that could maintain variation in aggressive behaviours within natural populations.

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Breeding density, not life history, predicts interpopulation differences in territorial aggression in a passerine bird

Cited by 46 publications

References 46 publications

Agonistic urban birds: elevated territorial aggression of urban song sparrows is individually consistent within a breeding period

Agonistic urban birds: elevated territorial aggression of urban song sparrows is individually consistent within a breeding period

Advantages of nonlinear mixed models for fitting avian growth curves

Experimental evidence that density mediates negative frequency‐dependent selection on aggression

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