An Amazing Bird Journey

A marathon is an athletic endeavour that most people never achieve. However, millions and millions of birds make a migratory trek over hundreds, sometimes thousands, of kilometres twice each year, dwarfing a marathon by far!

The Swainson’s Thrush (Catharus ustulatus) is a true long-distance migrant that can be found breeding in the northern Boreal regions of Canada and Alaska and overwintering as far south as tropical forests in Argentina. The Swainson’s Thrush is segregated into two distinct geographic populations: the “russet-backed” group of the Pacific coastline, and the “olive-backed” group of the interior and east. Although similar in appearance, these two groups diverge in their amazing migratory journeys. The russet-backed group takes a direct route along the west coast and overwinters primarily in Central America and Mexico. The olive-backed group takes a more easterly route for migration. This means that some of these birds must travel east prior to beginning their southward fall migration, making the journey even longer – especially since they overwinter farther south than their russet-backed Pacific counterparts. These divergent migratory paths are thought to be related to colonization patterns of the species post-glaciation in North America.

Figure 1. Researchers deployed geolocators on Swainson’s Thrush at a number of sites across their western range, including Point Reyes National Seashore in California, coastal and inland sites in British Columbia, Rocky Mountain National Park in Colorado, and most recently, Denali National Park. The resulting location data confirmed the direct and cross-continent migration paths of the coastal and inland populations and also helped define wintering areas for the various populations (Delmore et al. 2012, Cormier et al. 2013, Delmore & Irwin 2014). The russet-backed population is illustrated by the orange and yellow lines; the olive-backed population is illustrated by blue and purple lines; and, a hybrid population is denoted by the green line.  Figure and caption adapted from Philips 2018 (

The MOTUS Wildlife Tracking System is also uncovering some interesting migratory patterns for the Swainson’s Thrush and the closely related Gray-cheeked Thrush (Catharus minimus). For example, one Swainson’s Thrush was tracked travelling at least 175 km per day for a month, for a total of nearly 6,000 km in 34 days! This bird also spent some of the winter at a shade-grown coffee plantation.

To survive these arduous long-distance journeys, safe havens that provide food, water, and shelter are crucial for the Swainson’s Thrush and many other species. The Swainson’s Thrush breeds primarily in coniferous forests in the Boreal region but can be found in a wider variety of habitats during migration. Try to incorporate native shrubs and tall trees in your garden to provide shelter for these birds. They prefer to feast on insects during the breeding season, and they incorporate fruit into their diet in fall and winter. Planting a diversity of native food-bearing and insect-attracting plants in your garden can help these birds to fuel up while visiting your garden.

Listen for the upward-spiralling, flutelike song of the Swainson’s Thrush as they pass through your garden during their annual spring migration or in their breeding range. Their ethereal song will add a sense of wonder to your outdoor space. By gardening for birds, you can help many species thrive, including the Swainson’s Thrush.