The Function(s) of Bird Song

Male bird song may attract and stimulate females and may repelmales, but the evidence that song is essential for accomplishingthese "main functions" is not abundant. Correlations betweenmale song traits (such as repertoire size or singing rate) andcomponents of fitness reveal that important information, perhapsabout overall male quality, is available for listeners. To determinewhether birds use that information, however, will require researchersto manipulate song traits independently of male quality. Havingthen determined more rigorously the "current utility" of song,we will more clearly be able to infer how selection has shapedparticular song traits. We envision progress in understandingthe function(s) of bird song if investigators 1) thoroughlydescribe natural events, 2) use lucidly stated, multiple workinghypotheses, 3) realize the potential differences in song functionamong divergent taxonomic units, 4) transcend correlationalstudies by doing ingenious manipulative experiments, and 5)reason carefully when developing scenarios of evolutionary origin.     

猛禽中的捕蛇者

古今中外,雕在人类的以上中往往与天界和神祗的权利联系起来,象征着力量、骄傲和权力。人们认为雕是神的信使,因为它强壮有力,飞的很高,古希腊人相信,神祗是不是会伤害自己的信使的,于是雕被捆在庙宇的屋顶上,以防止闪电击毁建筑人。希腊人和罗马人认为雕有治愈创