Description and ecology

Eastern Bluebirds (Sialia sialis) are medium-sized (~18 cm) songbirds in the True Thrush Family (Turdidae). It is one of 3 species in North America – the other two species, the Western Bluebird (Sialia mexicana), and Mountain Bluebird (Sialia currucoides) occur in the Rocky Mountain Region of Western North America. Eastern Bluebirds are found in open habitats, such meadows, tallgrass prairies, savannas, and shrublands – across Eastern North America. The breeding range of Eastern Bluebirds extend from northern Ontario to central Florida, with a secondary range in the cordilleras in Mesoamerica. They are a year-round resident species throughout most of their range, including the Long Point Basin, but are short-distance migrants in northern regions, such as Algoma, Manitoulin Island, Algonquin Park, and Michigan’s Upper Peninsula. Throughout Ontario, they are most common in the spring and summer months. Male Eastern Bluebirds have a deep blue head, throat, and wings, with a deep orange belly. Females have similar colouration to males, but are paler overall, sometimes appearing grey rather than blue. They are the smallest of the true thrushes, substantially smaller than the American Robin (Turdus migratorius), Wood Thrush (Hylocichla mustelina), and the Catharus thrushes. Eastern Bluebird songs consist of a melodic warble, up to 3 notes per phrase. This song is almost exclusively sang by males, typically from a high perch in an attempt to attract a mate.

In the Great Lakes Region, the Eastern Bluebird breeding season begins in late March, when males become more territorial. Males will display potential nest cavities, and bring nesting material, while singing loudly to the females. After a breeding pair is established, the female builds the nest, consisting of a cup-shaped nest comprised of vegetation within a tree cavity or nest box. Of all Long Point’s native thrushes, Bluebirds are only species that are cavity nesters – despite being primarily a meadow bird. Female Eastern Bluebirds lay 3-6 eggs per clutch. For each brood, the incubation period is around 13 days, and the nestling raising period is around 17-21 days. Per summer, Eastern Bluebirds typically raise 2-3 broods per year from May through July. In open habitats, Eastern Bluebirds will often compete with Tree Swallows for nesting habitat In August, Eastern Bluebirds move towards their foraging habitats.

Eastern Bluebird are both insectivorous and frugivorous, with exact proportion varying seasonally. In the summer months, Eastern Bluebirds eat insects such as crickets, grasshoppers (both belonging to the order Orthoptera), beetles (Coleoptera) and caterpillars (Lepidoptera). When autumn arrives, insect numbers plummet, and Bluebirds shift their diet to sumac (Rhus sp., especially Rhus typhina, the Staghorn Sumac), blueberries (Vaccinium sp.), cherries (Prunus sp.), hawthorns (Crataegus sp.), Black Tupelo (Nyssa sylvatica), currants (Ribes sp.), holly (such as winterberry, Ilex verticillata), dogwood (Cornus sp.), hackberries (Celtis sp.), honeysuckle (Lonicera sp., Diervilla sp.), bayberry (Myrica pensylvanica sp.), pokeweed (Phytolacca americana), and juniper (Juniperus sp.). They continue consuming fruit until spring replenishes insect populations, restarting the yearly cycle.

In the Long Point Basin of Norfolk and Elgin Counties, large swathes of prairie and meadow habitats have been restored by conservation organizations in recent decades, either as the early-stage of an eventual reforestation project, or long-term grassland restoration project intended to support wildlife species specifically adapted to open habitats. These restoration projects, combined with the installation of nest boxes for breeding habitat, have benefited populations of Eastern Bluebird. Wildlife has flourished here – in contrast with many other areas of southwestern Ontario, which have faced severe declines in many species, primarily due to habitat loss and agricultural intensification. As more conservation lands are added – Eastern Bluebirds and many other species may have a bright future ahead in Norfolk.

Fun facts

• Eastern Bluebirds have excellent eyesight – with the ability to spot insects over 20m away!
• In June, during the peak of breeding season, Eastern Bluebirds can eat hundreds of insects daily, helping control pest populations
• In the mid-20th century, Bluebird populations were sharply declining due to habitat loss and competition from introduced species (like House Sparrows and European Starlings). However, nest box programs implemented across the continent by dedicated volunteers have been incredibly successful, reversing this decline!
• Eastern Bluebirds have high nest-site fidelity. They often return to the same breeding location year after year. Bluebirds will often use the same nest box or tree cavity multiple times per season, especially if the first brood is successful.

 

Written by Matthew Palarchio, HBSc in Environmental Sciences, Western University

All photos are Stock photos retrieved from Canva

 

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