Brenowitz E A, Baptista L F, Lent K, Wingfield J C
Department of Psychology, University of Washington, Seattle 98195, USA.
J Neurobiol. 1998 Jan;34(1):69-82. doi: 10.1002/(sici)1097-4695(199801)34:1<69::aid-neu6>3.0.co;2-a.
Seasonal plasticity in the morphology of telencephalic nuclei that control song behavior has been reported for diverse species of songbirds. The only published report of a lack of seasonal changes in the song nuclei of a seasonally breeding bird is that of Baker et al. in the Nuttall's subspecies of white-crowned sparrow (Zonotrichia leucophrys nuttalli). In this study, they brought wild birds into the laboratory and exposed them to either "summer" or "winter" photoperiods. Previous studies have shown that exposing wild-caught white-crowned sparrows to long-day photoperiods in the laboratory may not induce circulating concentrations of testosterone (T) as high as those seen in wild breeding birds. Changes in circulating T are primarily responsible for the seasonal morphological changes in the song nuclei. To determine whether there is seasonal plasticity of the song system in this subspecies, we measured circulating T, morphological attributes of the song nuclei, and song behavior in wild Nuttall's white-crowned sparrows during the spring and fall. Testis size and circulating T concentrations were greater in spring than fall birds. The absolute volumes of the song nuclei HVc, RA, and Area X, and their volumes relative to those of either the total telencephalon or three thalamic nonsong nuclei, were significantly greater in the spring than fall sparrows. Song behavior also changed seasonally; fall birds sang shorter songs than did spring birds. These results show that there is seasonal plasticity of the song system in wild Nuttall's white-crowned sparrows. Seasonal plasticity can now be regarded as a common feature of the seasonally breeding songbirds studied thus far.
已有报道称，多种鸣禽控制鸣叫行为的端脑核形态存在季节性可塑性。关于季节性繁殖鸟类的鸣叫核缺乏季节性变化的唯一已发表报告是贝克等人对白冠雀纳塔尔亚种（Zonotrichia leucophrys nuttalli）的研究。在这项研究中，他们将野生鸟类带入实验室，使其暴露于“夏季”或“冬季”光周期下。此前的研究表明，在实验室中将野生捕获的白冠雀暴露于长日照光周期下，可能不会诱导其循环睾酮（T）浓度达到野生繁殖鸟类的水平。循环T的变化是鸣叫核季节性形态变化的主要原因。为了确定该亚种的鸣叫系统是否存在季节性可塑性，我们在春季和秋季测量了野生纳塔尔白冠雀的循环T、鸣叫核的形态特征以及鸣叫行为。春季鸟类的睾丸大小和循环T浓度高于秋季鸟类。鸣叫核HVC、RA和X区的绝对体积，以及它们相对于整个端脑或三个丘脑非鸣叫核的体积，在春季明显大于秋季麻雀。鸣叫行为也存在季节性变化；秋季鸟类的鸣叫比春季鸟类短。这些结果表明，野生纳塔尔白冠雀的鸣叫系统存在季节性可塑性。季节性可塑性现在可以被视为迄今为止所研究的季节性繁殖鸣禽的一个共同特征。
