|"Tufted Titmouse (Parus bicolor) has expanded steadily
northwards in the 20th Century, aided by the regular supplies of food provided by man in the late winter and spring."-Harrup and Quinn in Chickadees, Tits, Nuthatches and Treecreepers
Christmas Bird Count data do indeed confirm
this statement by Harrup and Quinn. As seen on the animated map below, BirdSource
technology uses Christmas Bird Count data to depict the Tufted Titmouse's gradual
expansion into the upper mid-Atlantic states, New England, and Canada between 1901 and
1997. Note the relative stability of the boundary in the upper Midwest (in other words,
Minnesota), compared to the dramatic spread northward in the Northeast. Presumably, this
difference reflects the much harsher winters in the center of this continent-winters that
occasionally push Tufted Titmice populations south.
The animated map includes all sightings of
Tufted Titmice during Christmas Bird Counts in 10-year intervals, starting from 1901 to
The red dots on the map indicate where Tufted Titmice were observed, whereas the gray dots
indicate Christmas Bird Count Circles where these birds were not observed.