Nature Smart: What drives irruptions with bird species?

Nature is fluid and adaptive. Once you wrap your head around that simple truth, answering some of nature’s questions becomes easier.
For example, every few years, several bird species such as the common redpoll, pine siskin, evening grosbeak and others move out of their normal winter ranges and into other areas to seek food. This group of birds is usually referred to as the “winter finches,” and this mass movement of a group of birds is called an “irruption.”