Small birds, plain olive or gray above, white to yellow below, vireos are often confused with warblers but are actually more closely related to shrikes. Feeding high up in deciduous trees, vireos are best recognized in breeding season by their distinctive songs. They are distinguished from warblers by their relatively stouter bills and slower movements as they forage in trees for berries, insects and larvae. This family of approximately fifty species of songbirds is limited to the Western Hemisphere. Of the fifteen species found in North America, five extend their range to Saskatchewan. Red-eyed (Vireo olivaceus) and warbling vireos (V. gilvus) are widely distributed. Blue-headed (V. solitarius) and Philadelphia vireos (V. philadelphicus) are largely restricted to the boreal forest except during migration; the yellow-throated vireo (V. flavifrons) breeds only in the extreme southeast corner, in Moose Mountain and the lower Souris Valley.
The red-eyed vireo occurs in wooded areas throughout the province; it is scarce and local in the grasslands. More clearly marked than most vireos, it is distinguished by a black-bordered white eyebrow line and a gray cap. Its oft-repeated song, a series of separate phrases, is a frequently heard woodland sound, even at the height of summer. The warbling vireo, one of the plainest of vireos, olive-backed with a pale white eyebrow line, can be found in treed areas in the southern half of the province. Its song is a continuous warble, unlike the broken phrases of other vireos. The Philadelphia vireo is an uncommon summer resident of the boreal forest, occasionally noted in the parklands. Its song is similar to that of the red-eyed vireo, but higher and slightly slower. Philadelphias show more yellow below than other vireos except the yellow-throated vireo. The blue-headed vireo, fairly common in the northern mixed forests, can be identified by distinctive white eye rings, a gray head, white throat, and barred wings. The rarest of our vireos, the yellow-throated, has a bright yellow throat, yellow eye rings, and barred wings. It is most likely to be seen in Moose Mountain Provincial Park.
J. Frank Roy