Brain size is a key factor determining the performance and fitness of an organism; birds with relatively larger brains might have advantages in the utilization of resources and dispersal. Bite force is another important indicator of fitness, and plays an essential role in intra- and inter-specific competition. In this study, a comparative analysis was conducted on the head size and bite force of the two sister species, the white-rumped munia (Lonchura striata) and scaly-breasted munia (L. punctulata) that differ in distribution range. The results showed that the scaly-breasted munia, which has a wider distribution range, had a significantly larger head size than that of the white-rumped munia. In addition, scaly-breasted munias had a greater bite force; however, the difference was not significant. One possible explanation could be that the smaller head to body ratio in scaly-breasted munias reduced their bite-force slightly. Further, this finding could be attributed to the fact that similar food resources and foraging habitats of the two species lead to a similar bite force. Our study supported the argument that head size, rather than bite force, plays a more important role in the dispersal and evolutionary adaptation of birds.

大脑大小是决定生物体性能和适应性的关键因素；大脑相对较大的鸟类可能在资源利用和传播方面具有优势。咬合力是健康的另一个重要指标，在种内和种间竞争中起着至关重要的作用。在这项研究中，对两个姐妹物种白臀鲣（Lonchura striata）和鳞胸鲢（L. punctulata）的头部大小和咬合力进行了比较分析。) 分布范围不同。结果表明，分布范围更广的鳞胸鸫的头部尺寸明显大于白臀鲟。此外，鳞胸鲟的咬合力更大；然而，差异并不显着。一种可能的解释可能是，鳞胸鲟中较小的头身比略微降低了它们的咬合力。此外，这一发现可能归因于两个物种相似的食物资源和觅食栖息地导致相似的咬合力。我们的研究支持这样的论点，即头部大小，而不是咬合力，在鸟类的传播和进化适应中起着更重要的作用。