Such irruptions have not been seen since 1952. Larger groups may form during irruptions, migration or around a particularly large fruiting tree. It was extremely abundant during the 1880s and irruptions occurred in a number of locations. The resulting violence lasted, with irruptions of tranquility, into the fourteenth century. Black-backed woodpeckers are generally non-migratory but historically have undertaken intermittent irruptions.