Swainson's thrush
Bird activity at the yard is slowing down with the cold, wet weather.
The numbers of species and individuals is down significantly from a few days ago.
Territorial disputes between males often take the form of singing duels, with song volume and frequency escalating until the combatants’ physical exertions are clearly evident. During these contests, rivals very occasionally invert their customary melody so that it spirals downward in pitch. A sing-off can lead to a chase and even occasionally to physical attack.
source- allaboutbirds-org
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