英語(yǔ)時(shí)差：北美燕八哥2

Before a group of young cowbirds had time to socialize much, West had them stay the winter with a group of canaries. In the spring they were turned loose in an aviary with a mixed group of birds. What happened was weird: the cowbirds sang like canaries, and tried to court canaries. They ignored the other cowbirds! And the canaries ignored their advances. After the mating season–which these birds were really unsuccessful in, by the way–the cowbirds spent the next winter with a group of their own kind. The following spring they were again turned loose with a mixed group of birds, and this time they behaved like cowbirds. They sang cowbird songs, made cowbird moves, and did those things that would increase the cowbird population. What this means is that the cowbirds have to learn how to behave like cowbirds–it doesn’t just come naturally.