Wood Thrushes are a species of migratory songbird that breed in eastern North America and winter in Central America. During their spring and fall migrations between breeding and wintering grounds, Wood Thrushes are primarily nocturnal migrants, meaning they migrate at night.
When Do Wood Thrushes Migrate?
Wood Thrushes migrate north to their breeding grounds between March and May and migrate south to their wintering grounds between September and November. The exact timing of migration varies by location and weather conditions each year.
Spring Migration
In spring, Wood Thrushes generally begin migrating north in March in the southern U.S. Migration peaks in April and early May as they reach northern portions of their breeding range in the U.S. and Canada.
Fall Migration
Fall migration to wintering grounds begins earlier, usually in late August and September. Migration peaks in September and October with most individuals arriving on wintering grounds by early November.
Nocturnal Migration Patterns
Wood Thrushes maximize use of nocturnal flights during migration. They typically depart stopover sites around dusk and fly most actively during the first few hours of night.
Evening Take-offs
Wood Thrushes generally initiate migratory flights each night within 1-2 hours after sunset. After sunset, they become restless and exhibit migratory restlessness behaviors like pointing in their departure direction. This indicates they are ready to migrate and depart shortly after nightfall.
Nocturnal Flight Period
Once in flight, Wood Thrushes migrate most actively for 3-6 hours after sunset. They fly highest and most directed early in the night. Activity and altitude then gradually decrease overnight.
Morning Landings
Wood Thrushes end nocturnal flights and descend to stopover sites in the few hours before sunrise. They are seldom observed migrating after sunrise and instead forage and rest during the day.
Weather Influences on Migration Timing
Local weather conditions each night influence exactly when Wood Thrushes depart stopover sites and how long they remain in flight.
Ideal Migration Conditions
Wood Thrushes select nights for migration based on favorable wind and weather. Nights with tailwinds blowing in the direction of travel, clear skies, and cool temperatures are ideal. These conditions allow for efficient long-distance flights.
Poor Migration Conditions
On nights when conditions deteriorate due to storms, high winds, fog, precipitation, or heat, Wood Thrushes are less likely to migrate. They may descend early or choose not to depart stopover sites on very poor nights.
Stopover Patterns During Migration
Wood Thrushes migrate using a pattern of multi-day flights interspersed with stopovers to rest and refuel. The need for stopovers influences how many hours they can spend flying each night.
Duration of Nocturnal Flights
Wood Thrushes generally cannot sustain migration flights for more than 6-10 hours at a time due to energy reserves. Flights longer than 4-6 hours require a subsequent stopover to recover before migrating again.
Stopover Length
The duration of stopovers depends on how far a bird flew the previous night and conditions at the stopover site. Short fights of 2-4 hours may only require a short stopover of 1-2 days. Long flights need longer stopovers of up to 2 weeks to fully refuel fat stores before migrating again.
Conclusion
In summary, Wood Thrushes are nocturnal migrants that generally fly for several hours after sunset each night of migration. Their migratory behavior is influenced by weather conditions and the need for periodic stopovers to rest and feed. Understanding their nocturnal flight patterns provides insight into the remarkable migrations of these songbirds.
