College of Life Science, Hebei University, Baoding 071000, China.
College of Life Science, Hebei University, Baoding 071000, China; College of Biology and Food Science, Hebei Normal University for Nationalities, Chengde 067000, China.
Behav Processes. 2022 Aug;200:104706. doi: 10.1016/j.beproc.2022.104706. Epub 2022 Jul 14.
Territorial animals show less aggression during intrusion by neighbours than by strangers, a phenomenon known as the "dear enemy effect". Recent studies have shown that the dear enemy effect is variable in some birds throughout the breeding season. However, there is limited research on changes in dear enemy effects in songbirds during the breeding season. In this study, we monitored dusky warblers (Phylloscopus fuscatus) throughout their breeding stages, conducting playback experiments simulating incursions by neighbours and strangers during their egg-laying and incubation/nestling periods, and recording physical responses and song responses from territory owners. The results showed that male dusky warblers responded similarly to neighbours and strangers during the female egg-laying period, but there was a significantly stronger response to strangers than to neighbours during the incubation/nestling period. This suggests that male dusky warblers adjust the intensity of their defences against neighbours according to the reproductive status of their own mate. This may be because neighbouring males threaten the paternity of territorial males during the egg-laying period, so territorial males demote the 'dear enemy' friendly relationships with their neighbours to defend their mate and paternity. In contrast, during the non-reproductive period of females, when neighbours are less of a threat to the paternity of territorial males, lowering defences against neighbouring males allow them to devote more time and energy to activities that improve their fitness, such as foraging and seeking extra-pair mating.
领域动物在受到邻居入侵时比受到陌生人入侵时表现出更少的攻击性，这种现象被称为“亲爱的敌人效应”。最近的研究表明，在繁殖季节，一些鸟类的亲爱的敌人效应是可变的。然而，关于繁殖季节鸣禽亲爱的敌人效应变化的研究有限。在这项研究中，我们在整个繁殖阶段监测了暗绿柳莺（Phylloscopus fuscatus），在产卵和孵卵/育雏期间通过播放实验模拟邻居和陌生人的入侵，并记录领地所有者的身体反应和歌声反应。结果表明，雄性暗绿柳莺在雌性产卵期间对邻居和陌生人的反应相似，但在孵卵/育雏期间对陌生人的反应明显强于对邻居的反应。这表明，雄性暗绿柳莺根据配偶的繁殖状态调整对邻居的防御强度。这可能是因为在产卵期间，邻域雄性会威胁到领地雄性的亲权，因此领地雄性会将与邻居的“亲爱的敌人”友好关系降级，以保护其配偶和亲权。相比之下，在雌性的非繁殖期，当邻居对领地雄性的亲权威胁较小时，降低对邻域雄性的防御可以让它们有更多的时间和精力投入到提高适应度的活动中，例如觅食和寻找额外的交配机会。
