“An irruption is the sudden change in the population density of an organism. In North American birds, irruptions often refer to the movement of northern-wintering species to the south in years of low food availability. You can recognize irruptive movement patterns at your feeders: some winters you may see a species at your feeders in great numbers, but in other winters they don’t show up at all.”
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GR: Here’s a volunteer citizen naturalist opportunity for everyone, but especially for those who love birds.