Lane Samuel J, Sewall Kendra B
Virginia Tech, Department of Biological Sciences, 1405 Perry Street, Blacksburg, Virginia, 24061.
Virginia Tech, School of Neuroscience, 1405 Perry Street, Blacksburg, Virginia, 24061.
Integr Comp Biol. 2022 Jul 5. doi: 10.1093/icb/icac106.
The costs and benefits of breeding behaviors are influenced by environmental conditions, and habitat variation can shift the degree to which behaviors are expressed. Novel urban habitats have been shown to differ significantly in disturbances such as noise, light at night, and human presence, as well as resource availability, compared to rural habitats. Perhaps because of these environmental differences, urban males of several species are consistently more aggressive than rural males, raising the hypothesis that greater territorial aggression is beneficial in urban habitats. Though often ignored, female songbirds of many species also perform aggressive territorial behaviors towards conspecifics during the breeding season. For socially monogamous songbirds, this aggression functions to ensure partner fidelity and secure resources for reproduction. Studies of the effects of urbanization on songbird behavior have yet to determine if urban females also express greater territorial aggression. Importantly, energetically demanding behaviors such as territoriality and parental care should constrain one another, leading to behavioral trade-offs during the breeding season. Though territorial aggression and parental care are inversely related in males of several species of songbird, this relationship is understudied in female songbirds, particularly those facing environmental change such as urbanization. In this study, we compared aggressive signaling and a measure of parental care (maternal nest visitation rates) between female song sparrows (Melospiza melodia), living in urban and rural habitats. We hypothesized that female aggressive signaling would be higher in urban environments compared to rural, and negatively correlated with maternal visitation rates. We found that urban females, like males, expressed increased aggressive signaling compared to rural. However, female aggressive signaling was not related to our measure of maternal care, suggesting females aren't facing a trade-off between these two behaviors. Collectively, our results are consistent with the hypothesis that urban habitats promote territorial aggression in female song sparrows. As urbanization continues to spread, understanding the behavioral changes animals employ in urban environments requires studying individuals of different sexes and age classes, and will help us understand how some species are able to cope with human induced rapid environmental change.
繁殖行为的成本和收益受到环境条件的影响，栖息地的变化会改变行为表现的程度。与农村栖息地相比，新型城市栖息地在噪音、夜间光照和人类存在等干扰以及资源可用性方面存在显著差异。也许是由于这些环境差异，几种物种的城市雄性比农村雄性始终更具攻击性，这就提出了一个假设，即更强的领地攻击性在城市栖息地是有益的。尽管常常被忽视，但许多物种的雌性鸣禽在繁殖季节也会对同种个体表现出攻击性的领地行为。对于实行社会一夫一妻制的鸣禽来说，这种攻击性的作用是确保伴侣忠诚并为繁殖确保资源。关于城市化对鸣禽行为影响的研究尚未确定城市雌性是否也表现出更强的领地攻击性。重要的是，诸如领地行为和育雏等需要消耗能量的行为应该相互制约，从而在繁殖季节导致行为权衡。尽管在几种鸣禽物种的雄性中，领地攻击性和育雏行为呈负相关，但在雌性鸣禽中，尤其是那些面临城市化等环境变化的雌性鸣禽中，这种关系尚未得到充分研究。在本研究中，我们比较了生活在城市和农村栖息地的雌性歌雀（Melospiza melodia）之间的攻击性信号和一种育雏行为指标（母鸟巢穴探视率）。我们假设，与农村环境相比，城市环境中的雌性攻击性信号会更高，并且与母鸟探视率呈负相关。我们发现，与农村雌性相比，城市雌性与雄性一样，表现出更强的攻击性信号。然而，雌性攻击性信号与我们的育雏行为指标无关，这表明雌性在这两种行为之间没有面临权衡。总体而言，我们的结果与城市栖息地促进雌性歌雀领地攻击性的假设一致。随着城市化的持续蔓延，了解动物在城市环境中所采用的行为变化需要研究不同性别和年龄组的个体，这将有助于我们理解一些物种如何能够应对人类引发的快速环境变化。
