They are carrying out research to establish exactly why so many species of songbird are disappearing.他们正在进行研究以确定那么大量种类的鸣禽灭绝的原因。Pesticides destroy insects that are an important part of the food chain for several species of songbird.农药把对于一些种类的鸣禽来说是食物链中重要一环的昆虫消灭了。Despite their large size, crows are members of the songbird family.乌鸦个头虽大，但还是属于鸣禽科。