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

Davies, Scott; Sewall, Kendra B.

doi:10.1098/rsbl.2016.0315

Cited by 41 publications

(48 citation statements)

References 14 publications

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“…The ornithological literature already offers many examples of adjustments in urban birds compared to rural conspecifics that are concordant with this expectation (see recent review in Marzluff, 2017). Urban birds are usually more aggressive (e.g., Minias, 2015;Davies and Sewall, 2016), bolder (e.g., Ducatez et al, 2017), can be approached more closely by humans (e.g., Lin et al, 2012;Møller et al, 2015), are less neophobic (e.g., Tryjanowski et al, 2016), have higher levels of disturbance tolerance (Lowry et al, 2013) and reduced levels of physiological stress response (e.g., Partecke et al, 2006;Minias, 2015). Other empirical comparisons between urban and rural birds have also suggested shifts in breeding strategies: urban birds usually have earlier laying dates, smaller clutch sizes, lower reproductive success (e.g., Peach et al, 2008;review in Chamberlain et al, 2009), and higher adult survival rates (e.g., Rebolo-Ifran et al, 2015).…”

Section: Introductionmentioning

confidence: 54%

Urbanization Is Associated with Divergence in Pace-of-Life in Great Tits

et al. 2017

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As an extension of the classic life history theory, the recently highlighted pace-of-life syndrome hypothesis predicts the coevolution of behavioral, physiological and life-history traits. For instance, bolder and shyer individuals do not only differ in personality profiles, but also in neuro-endocrinology and breeding patterns. While theory predicts that bolder (i.e., proactive), more aggressive individuals should colonize more rapidly urbanized habitats than shyer (i.e., reactive), less aggressive individuals, it is also predicted that across generations, adaptive selection processes could favor shyer individuals that are more sensitive to novel environmental cues. Here we compared two personality traits (handling aggression, exploration score in a novel environment), one physiological trait related to stress response (breath rate) and four breeding traits (lay date, clutch size, hatching success and fledging success) in a rural and an urban study population of Mediterranean great tits Parus major. Mixed models revealed strong phenotypic divergence between forest and city in most traits explored, in particular in personality, whereby urban great tits were more reactive to stress and faster explorers compared to rural birds (yet not more aggressive). Urban birds also laid smaller broods earlier in spring compared to their rural conspecifics, and city broods resulted in lower hatching success yet interestingly fledging success was similar. Nest-box centered measures of anthropogenic (artificial light, pedestrians, and cars) perturbation and resource abundance allowed us to go beyond the classical forest/city comparison by exploring the phenotypic variation across an urbanization gradient. This revealed that high urbanization in nest-box surroundings was associated overall with earlier breeding and smaller clutches, but also with faster breath rate, although these trends showed strong annual variation. Ongoing rapid urbanization and non-random gene flow between rural and urban great tits could both contribute to the high prevalence of bold breeders in the city. Our study suggests the existence of urban and rural great tit ecotypes with different pace-of-life, but also a finer-scale divergence along the degree of urbanization within the city. Future studies are required to determine whether this phenotypic variation at different spatiotemporal scales is adaptive and whether it has a genetic basis or results from phenotypic plasticity.

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Section: Introductionmentioning

confidence: 54%

Urbanization Is Associated with Divergence in Pace-of-Life in Great Tits

et al. 2017

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“…Song sparrows are an excellent illustration of this, as multiple research groups have shown that urban male song sparrows are more aggressive toward conspecifics than their rural counterparts (Evans et al, 2010;Foltz et al, 2015b;Davies and Sewall, 2016). Further, male song sparrows living in urban habitats are more bold in response to heterospecific alarm calls and human approach than are rural males, though only response to alarm calls is correlated with conspecific aggression (Evans et al, 2010;Scales et al, 2011;Myers and Hyman, 2016).…”

Section: Introductionmentioning

confidence: 99%

“…Prior studies have failed to find reliable differences in levels of the avian stress hormone, corticosterone, between rural and urban songbirds despite predictions that urban habitats could impact stress reactivity (Partecke et al, 2006;Bonier et al, 2007;Schoech et al, 2007;Fokidis et al, 2009Fokidis et al, , 2011Atwell et al, 2012;Bonier, 2012;Foltz et al, 2015a). Nor have consistent differences been reported in levels of testosterone, a hormone traditionally thought to promote aggression in vertebrates (Partecke et al, 2005;Fokidis et al, 2011;Deviche and Davies, 2013;Atwell et al, 2014;Davies and Sewall, 2016;. Failure to find differences in circulating hormone levels suggest that reliable behavioral differences may be underpinned by deeper brain mechanisms, yet little work has explored how urbanization and neural function may be interrelated.…”

Section: Introductionmentioning

confidence: 99%

“…Understanding the origins of such differences across habitat types requires addressing both ultimate explanations and proximate mechanisms of behavior. Increased boldness or aggression in urban male song sparrows could be a response to resource availability (Foltz et al, 2015b) or differences in conspecific density (though see Davies and Sewall, 2016). However, regardless of the fitness benefit of the behavior, proximate mechanisms must mediate behavioral differences.…”

Section: Introductionmentioning

confidence: 99%

“…However, regardless of the fitness benefit of the behavior, proximate mechanisms must mediate behavioral differences. Despite repeated demonstrations of behavioral differences in song sparrows living along urban-rural gradients, the neural and physiological basis of differences in aggression are not fully understood (Evans et al, 2010;Foltz et al, 2015a;Davies and Sewall, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Two Neural Measures Differ between Urban and Rural Song Sparrows after Conspecific Song Playback

Sewall

Davies

2017

Front. Ecol. Evol.

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Urbanization is a critical form of environmental change that can affect the physiology and behavior of wild animals and, notably, birds. One behavioral difference between birds living in urban and rural habitats is that urban males show elevated boldness or territorial aggression in response to simulated social challenge. This pattern has been described in several populations of song sparrow, Melospiza melodia. Such behavioral differences must be underpinned by differences in the brain, yet little work has explored how urbanization and neural function may be interrelated. We explored the relationship between urbanization and neural activation within a network of brain regions, collectively called the social behavior network, which contributes to the regulation of territorial aggression. Specifically, we captured free-living, territorial male song sparrows by playing them conspecific songs for 6-11 min, and then collected their brains. We estimated recent neural activation, as indicated by the immediate early gene FOS, and measured levels of a neuropeptide, arginine vasotocin (AVT), which is involved in the regulation of social behavior. Based on previous studies we expected urban males, which are generally more territorially aggressive, to have lower FOS expression in a node of the social behavior network implicated in regulating territoriality, the lateral septum (LS). Additionally, we expected urban males to have lower AVT expression in a brain region involved in the regulation of sociality, the medial bed nucleus of the stria terminalis (BSTm). We found that, compared to rural males, urban male song sparrows did have lower FOS expression in the LS. This pattern suggests that lower neural activation in the LS could contribute to behavioral adjustments to urbanization in male song sparrows. Additionally, counter to our predictions, urban male song sparrows had higher AVT-like immunoreactivity in the BSTm. Future work building upon these findings is needed to determine the causal role of such neural differences across rural and urban habitats. Understanding the mechanisms impacted by urbanization will inform our understanding of the reversibility and consequences of this form of habitat change.

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Male aggressiveness and risk-taking during reproduction are repeatable but not correlated in a wild bird population

Salazar

García

Kuspiel

et al. 2021

Behav Ecol Sociobiol

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The existence of among-individual variation in behaviour within populations is poorly understood. Recent theory suggests that fine-scale individual differences in investment into current versus future reproduction may lead to a ‘slow-fast’-pace-of-life continuum, also referred to as the ‘pace-of-life-syndrome’ (POLS) hypothesis. According to this idea, individuals are predicted to differ in their level of risk-taking, which may drive among-individual variation and covariation of behaviours. Consistent individual differences in aggression, an ecologically relevant and potentially risky behaviour, have been reported across the animal kingdom. Here we test whether such individual differences in aggression are a manifestation of underlying differences in risk-taking. In a wild blue tit (Cyanistes caeruleus) population, we used standard behavioural tests to investigate if male territorial aggressiveness and risk-taking during breeding are positively related. At the start of breeding, we simulated conspecific territorial intrusions to obtain repeated measures of male aggressiveness. Subsequently, we measured male risk-taking as their latency to resume brood provisioning after presenting two different predators at their nest: human and sparrowhawk, a common predator of adult songbirds. First, we found substantial repeatability for male aggressiveness (R = 0.56 ± 0.08 SE). Second, while males took longer to resume provisioning after presentation of a sparrowhawk mount as compared to a human observer, risk-taking was repeatable across these two predator contexts (R = 0.51 ± 0.13 SE). Finally, we found no evidence for a correlation between male aggressiveness and risk-taking, thereby providing little support to a main prediction of the POLS hypothesis. Significance statement Consistent, and often correlated, individual differences in basal behaviours, such as aggression, exploration and sociability, are found across the animal kingdom. Why individuals consistently differ in their behaviour is poorly understood, as behavioural traits would seem inherently flexible. The ‘pace-of-life syndrome’ (POLS) hypothesis proposes observed behavioural variation to reflect differences in risk-taking associated with individual reproductive strategies. We tested this idea in a wild blue tit population by investigating whether individual males that were more aggressive toward territorial intruders also took more risk when provisioning their nestlings under a threat of predation. While we found consistent individual differences in both aggressiveness and risk-taking, these behaviours were not significantly correlated. Therefore, our study demonstrates among-individual variation in ecologically relevant behaviours in wild blue tits but provides little support for the POLS hypothesis.

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

Cited by 41 publications

References 14 publications

Urbanization Is Associated with Divergence in Pace-of-Life in Great Tits

Urbanization Is Associated with Divergence in Pace-of-Life in Great Tits

Two Neural Measures Differ between Urban and Rural Song Sparrows after Conspecific Song Playback

Male aggressiveness and risk-taking during reproduction are repeatable but not correlated in a wild bird population

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