Description and Ecology
Indigo Buntings (Passerina cyanea) are medium-sized (~14 cm) migratory songbirds in the Cardinal Family (Cardinalidae). Ontario has three native Bunting species, the Indigo Bunting, Blue Grosbeak (Passerina caerulea) and Painted Bunting (Passerina ciris). Of these, only the Indigo Bunting breeds regularly in Ontario. The other two species are usually observed for short time periods as vagrants / spring overshoots at the migratory bird hotspots along Lake Erie, such as Long Point, Rondeau, and Pelee (they subsequently reverse migrate south to find their proper breeding grounds in the eastern United States). Indigo Buntings prefer meadows and savannas throughout the Great Lakes Region.
Male Indigo Buntings are cyan (turquoise-blue) in the breeding season, which lasts from April to July. After nesting is finished, they moult into a patchy mix of blue and brown. Female Indigo Buntings are entirely brown in colour. The birdsong is described as a series of clear, high-pitched notes, each a few seconds in length (as typical for bird world, the loud and impressive melodies are vocalized almost exclusively by males, though females do sing some more subtle notes). They are the loudest at dawn, though they sing throughout the day. Indigo Bunting birdsong diminishes when August comes around, with vocalizations being calls than songs. By September, expect the dawn chorus to be gone on most days (you might hear the song of an vireo or flycatcher, such as the Eastern Wood Pewee, Contopus virens, if you are lucky). In late summer, Indigo Buntings begin congregating at migratory staging areas, where they forage in preparation for autumn migration. They usually arrive at their wintering grounds – the humid forests of Mesoamerica, from mid-October through November.
While Indigo Bunting are highly adaptable birds, they usually prefer meadows, oak savannas, or upland forests, usually arranged in a mosaic of open and forested habitats. This type of ecosystem is found in abundance throughout southern Ontario, and north into Manitoulin and the Algoma Region. It prefers more varied agricultural landscapes rather than intensively-managed monocultures – the Long Point Basin is almost perfect habitat for the species. Female Indigo Buntings usually place their nests within a metre from the ground. She builds and incubates the nest herself (usually within 3 days), while the male monitors the breeding territory for any nuisances or potential predators. The nest is an open cut of grass blades, leaves and other vegetation, with spider web used as structural support. Incubation, done entirely by the female, takes around 12 days, while the raising of hatched offspring to fledge takes another 11 days. The eggs are white, with a few subtle brownish spots.
Indigo Buntings are omnivorous (like other members of the Cardinal Family), feeding on both insects and fruit, though they mostly consume insects. They are described as foliage-gleaners, rummaging for insects on trees, shrubs, and other plants. Insects commonly consumed include butterflies and moths (Lepidoptera), beetles (Coleoptera), flies (Diptera), ants & bees (Hymenoptera), true bugs, such as aphids and cicadas (Hemiptera). They also consume spiders (Araneae).
These songbirds are common throughout most of their breeding range. Populations decline with the spread of intensive agriculture (which typically involves the removal of pastures and hedgerows – prime foraging habitat for Indigo Buntings), or contrastingly, reforestation, where trees outcompete the more preferred shrubland ecosystems used by Buntings for breeding. Throughout much of Eastern North America (including Central Ontario), there has been a reforestation trend where marginal shrublands, pastures, and open ecosystems have naturally reverted to closed-canopy forests. Areas left in agriculture (i.e., including much of southwestern Ontario) have intensified production, usually characterized by cash crops such as maize (corn) and soyabean. While this trend has accounted for a slight decline in Indigo Bunting populations within the previous few decades, the species is not of conservation concern.
Fun facts:
- Indigo Buntings do not have any blue pigment in their feathers. Like nitrogen gas in the sky, their feathers contain structures that scatter and refract blue light. This is why they appear blue.
- These birds are long-distance nocturnal migrants, using the stars of the night sky as navigation. Their annual journey covers thousands of miles.
- The global population of Indigo Buntings is estimated at over 70 million (as of the 2020s)
- Similarly to many other songbirds, Indigo Buntings can be victims of brood parasitism by Brown-headed Cowbirds (Molothrus ater), which thrives in similar habitats as Buntings.
Written by Matthew Palarchio, HBSc in Environmental Sciences, Western University
All photos are Stock photos retrieved from Canva
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