Geography/Habitat:

The MacGillivray’s Warbler, (Oporornis tolmiei (or Geothlypis tomiei)), was first described by John Kirk Townsend in 1839 in the Columbia River area of Vancouver. It forms a superspecies with the Mourning Warbler and there is some interbreeding where ranges overlap. There are 5 subspecies currently recognized.

The MacGillivray’s Warbler breeds in the Western US and Canada from California up to extreme South Alaska and as far East as New Mexico. It winters in Mexico and down through Central America.

Its breeds on the edge of forest clearings with a dense understory in both coniferous and deciduous forests. In migration found in varied habitats but it appears to favor dense understory, even here. In Winter, humid areas with dense scrub are preferred often near a water supply.

Breeding season is May to August. A grassy cup made of grass and twigs and lined with fine grass and hair is constructed very close to the ground in dense undergrowth. Three to six brownish eggs are laid and incubated by the female for 11 to 12 days. Once hatched the chicks spend a further 9-10 days being fed by both parents before fledging.

Food supply is primarily insectivorous including bugs, beetles and caterpillars. These are gleaned from dense understory close to the ground.

Identification

The MacGillivray’s Warbler is medium to large sized with olive green upperparts and yellow underparts. The head and upper breast are slate gray with the hood often being almost black on the breast. It has bold thick white eye arcs which are distinctive. The female is similar but typically less distinct and paler often with an almost whitish throat.

The songs are short rhythmic buzzing phrases and they call a repeated dry “chik-chik-chik”. MacGillivray’s are very vocal and often heard before they are seen.

Fun Facts

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• MacGillivray’s were once considered the same species as the Mourning Warbler
• MacGillivray’s Warbler was originally called Tolmies Warbler but was renamed by Audubon for his friend Dr. W. MacGillivray.
• A group of Warblers is known as a bouquet, a confusion, a fall or a wrench.