Fig. 1. Sketches show the plumage differences of the three Canada jay (Perisoreus canadensis) morphotypes (Boreal, Rocky Mountain, and Pacific) and the key tree species they are associated with (illustrations by Howard Coneybeare).

Boreal morphotypes are strongly associated with white spruce (Picea glauca), Rocky Mountain morphotypes are associated with Engelmann spruce (P. engelmanni), and Pacific morphotypes are not associated with any particular spruce species but are found in coniferous forests of the western subalpine. Map shows the distributions of the three Canada jay morphotypes across the contact in southwestern Canada and northwestern United States: Boreal (red), Rocky Mountain (yellow), and Pacific (green). Inset I) shows populations from further north in northern British Columbia and the Northwest Territories Canada. Pie charts show the nuclear genetic group that individuals were assigned to with STRUCTURE and GENODIVE (as found in Fig. 3): Boreal (red), Rocky Mountain (yellow), Pacific (green), and putative hybrids (purple). For information on the individuals included in each group, please see Table S1. Inset II) Map showing the distribution of white spruce (Picea glauca; light brown), Engelmann spruce (P. engelmanni; white), and western subalpine (dark gray), and the areas of overlap between white and Engelmann spruce (light purple), and western subalpine and Engelmann spruce (light blue) across the contact zone.