Common Redpoll
The term "irruption" refers to the movement of a species (or several
species) from an area where they typically occur into a region where they
are not normally present. The most common irruptions in North America are
of winter finches. These birds, which include Common Redpolls and
White-winged and Red Crossbills, normally winter in Canada but sometimes
irrupt into the United States during the winter.
When many species irrupt during the same year, it is called a
"superflight." To learn more about superflights, visit the 1997-98 North American Winter Finch and Red-breasted Nuthatch Survey site.
The map above shows the distribution of Common Redpoll in February during a
non-irruptive year, 1996-97. Based on reports from Project FeederWatch,
this interpolated surface shows higher abundance in darker shades of green.
The map below shows the distribution of Common Redpoll in February during
an irruptive year, 1997-98. Note the expansion of birds into the
northeastern U.S. and southern Canada. 1997-8.
The regularity of Common Redpoll irruptions can be seen in the
animated map below.
Learn more about winter finch irruptions by visiting the
Irruptive Bird Survey site