Some Swainson’s thrushes migrate to Argentina

Robyn Perkins
For the Lakeside Leader

The Lesser Slave Lake Bird Observatory (LSLBO) has been busy. We monitor bird activity daily rain or shine, but can only open the nets (we use to capture birds) when the weather is calm and warm. This latest glimpse of summer made this possible.

With good netting coverage, we have banded 511 birds this week, bringing our fall season total up to 2,160 birds banded from 44 species. Among these bands there has been a high number of two species that are commonly heard, but rarely seen: Swainson’s thrush and ovenbird.

Swainson’s thrush are our third most commonly banded species. They nest right on the ground and most of their time is spent on the forest’s floor where little light reaches. They have evolved large eyes to see in the dim light and subtle colours to blend in. Swainson’s thrush winter in regions as ‘close’ as Mexico, but can be found as far away as Argentina.

Similar to Swainson’s thrush, ovenbirds spend much of their time on the forest floor and have large eyes and dull colours. Although they may look like a thrush, they are actually a member of the warbler family. They are named after their nests placed on the ground with a woven roof resembling an oven onto which the female drops leaves and twigs to disguise it in the leaf litter. This species does not go quite as far as Swainson’s thrush and will winter in Central America, Florida, and Cuba.

Unlike many other songbird species that are commonly seen darting overhead on their way south, neither Swainson’s thrush nor ovenbirds are obvious in their migrations choosing instead to weave their way discreetly through the understory (plants under the main forest canopy). This means that we rely heavily on our nets to give us estimates of their population trends. Since they move through the forest, where our nets are placed, we are more likely to capture these species than we are to observe them through our binoculars.

Although we humans may take a long time to move any distance through the understory, these birds are quick. In 2012, we banded an ovenbird on August 12 that was sadly found dead 46 days later in Minnesota. Assuming this bird flew directly from the LSLBO to Minnesota (which it certainly did not), it traveled a distance of approximately 2,000 km. That’s an average speed of over 40 km per day! Even though this is an impressive feat for a bird weighing only 15 to 20 grams, it pales in comparison to Swainson’s thrush migration.

In a 2015 study, researchers tracked Swainson’s thrush on their northward journey and found one thrush went an astounding 6,000 km in just 34 days, flying at least 175 km per day.

Although the forest has grown silent with the conclusion of the breeding season, it is still a great time to go birding and experience the mysteries of migration!

Ovenbird
Swainson’s thrush

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