The connection between testosterone and territoriality in free-living songbirds has been well studied in a reproductive context, but less so outside the breeding season. To assess the effects of seasonal androgenic action on territorial behavior, we analyzed vocal and non-vocal territorial behavior in response to simulated territorial intrusions (STIs) during three life-cycle stages in free-living male black redstarts: breeding, molt and nonbreeding. Concurrently, we measured changes in circulating testosterone levels, as well as the mRNA expression of androgen and estrogen receptors and aromatase in the preoptic, hypothalamic and song control brain areas that are associated with social and vocal behaviors. Territorial behavior and estrogen receptor expression in hypothalamic areas did not differ between stages. But plasma testosterone was higher during breeding than during the other stages, similar to androgen receptor and aromatase expression in the preoptic area. The expression of androgen receptors in the song control nucleus HVC was lower during molt when birds do not sing or sing rarely, but similar between the breeding and the nonbreeding stage. Nevertheless, some song spectral features and the song repertoire differed between breeding and nonbreeding. Territorial behavior and song rate correlated with the expression of steroid receptors in hypothalamic areas, and in the song control nucleus lMAN. Our results demonstrate seasonal modulation of song, circulating testosterone levels, and brain sensitivity to androgens, but a year-round persistency of territorial behavior and estrogen receptor expression in all life-cycle stages. This suggests that seasonal variations in circulating testosterone concentrations and brain sensitivity to androgens is widely uncoupled from territorial behavior and song activity but might still affect song pattern. Our study contributes to the understanding of the complex comparative neuroendocrinology of song birds in the wild.

中文翻译：

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男性黑red的季节性歌曲和全年领土性的神经内分泌模式

自由繁殖的鸣禽中睾丸激素和地域性之间的联系已经在生殖方面得到了很好的研究，但是在繁殖季节以外则很少。为了评估季节性雄激素作用对领土行为的影响，我们分析了在自由生活的男性黑black的三个生命周期阶段，对模拟的领土入侵（STIs）的响应，声音和非声音的领土行为：繁殖，蜕皮和非繁殖。同时，我们测量了与社交和声音行为相关的视前，下丘脑和歌曲控制大脑区域中循环睾丸激素水平的变化，以及雄激素和雌激素受体和芳香化酶的mRNA表达。下丘脑区域的区域行为和雌激素受体表达在两个阶段之间没有差异。但是，在繁殖过程中血浆睾丸激素水平高于其他阶段，类似于视前区雄激素受体和芳香化酶的表达。当鸟类不唱歌或很少唱歌时，在蜕皮过程中，歌曲控制核HVC中的雄激素受体的表达较低，但在繁殖和非繁殖阶段相似。但是，在繁殖和非繁殖之间，某些歌曲的频谱特征和歌曲曲目会有所不同。领土行为和歌曲速率与下丘脑区域和歌曲控制核lMAN中类固醇受体的表达相关。我们的研究结果表明歌曲的季节性调节，循环的睾丸激素水平以及大脑对雄激素的敏感性，但在所有生命周期中，其行为和雌激素受体的表达全年都保持不变。这表明循环睾丸激素浓度和大脑对雄激素的敏感性的季节性变化与地域行为和歌曲活动没有很大关系，但仍可能影响歌曲模式。我们的研究有助于了解野生鸟类中复杂的比较性神经内分泌学。