The male Black-throated Blue Warbler is one of the most elegant and easily identified warblers in the eastern woods — deep midnight-blue above, with a black face, throat, and sides sharply divided from a clean white belly. The female could hardly look more different: a plain olive-brown bird with a subtle face pattern. What ties them together is a small but reliable white square at the base of the wing, a "handkerchief" mark present in both sexes and unique among Michigan warblers.
This warbler nests low in the dense shrub layer of mature deciduous and mixed forest, and in Michigan it breeds mainly in the northern part of the state where such understory-rich woods persist. Elsewhere it is a prized migrant in spring and fall. The male's husky, rising song — a lazy "zur-zur-zur-zree" — drifts up from the understory, and unusually among warblers, this species shows strong fidelity to specific mature forest tracts across years.
Gleans caterpillars, insects, and spiders from the undersides of leaves in the forest understory and midstory, often hovering briefly to pick prey. It adds berries and small fruit in late summer and on its Caribbean wintering grounds, where males and females tend to occupy different habitats.
Both sexes share a small white square at the base of the wing, the "handkerchief" or "pocket handkerchief" mark. It is the reliable clue that a plain olive-brown female is a Black-throated Blue Warbler.
Low in the dense shrub understory of mature deciduous and mixed forest, mainly in northern Michigan. It needs woods with a thick shrub layer, so it is absent from forests lacking that understory.
A husky, buzzy, rising series often written "zur-zur-zur-zree," with a lazy, upward-slurred ending. It is delivered from the understory and is fairly easy to learn.
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