Biology: The Study of Life - McGraw-Hill Education
But do crows “welcome” cuckoos, as Bechstein suggested? It’s probably a little more complicated than this. Crows nest communally—their bushy nests are often visible by the score in the bare branches of trees—and a previous study at this same field site showed that larger groups of crows' nests are less likely to be parasitized by cuckoos. If raising a cuckoo is so beneficial to the survival of crow chicks, we’d expect the opposite. Perhaps having other crows to help raise chicks also helps to deter predators, and the benefit of the cuckoo excretions no longer outweighs their cost.
SI unit that you might encounter in the study of biology
Many of the other cuckoo species that do not evict their nest-mates also emit similar foul fluids. So this study shows that it might be time to revisit our thoughts about why their hosts have not evolved defenses. In areas where there are many predators, even the smallest advantage conferred by a cuckoo chick may be sufficient to offset the evolution of defenses in the host species.
demonstrationfor "What Is Life?"to introduce some levity intothe classroom and to provide an opportunity to discuss the importanceof careful observations. One teacher from the suggested using whiteor golden raisens to makethem harder for students to recognize.