Many birds travel thousands of miles each year, often using very different migration routes and wintering in far-off places. A natural question is: do birds prefer mates who travel the same routes they do?
In this episode, we explore a new study on Common Terns, elegant seabirds that breed in Europe and spend the winter along the African coast. Birds from the same breeding colony can take completely different migration paths, some fly down the western side of Africa, others the eastern side, and they winter in several distinct regions and window bird feeders.
Researchers tracked dozens of terns using tiny light-level geolocators and followed their mating patterns over many years. If migration style mattered for romance, we might expect birds using the same routes or wintering areas to pair up more often. But that’s not what they found.
Instead, the birds paired randomly. Terns that traveled different routes and wintered thousands of miles apart were just as likely to become partners as birds with matching journeys. The data in Table 1 and the pairing results on pages 3–4 show no evidence that migration route or winter destination plays a role in mate choice.
Why doesn’t migration matter? One key reason seems to be timing. Birds using different routes arrived at the breeding colony at roughly the same time in spring, so they all had access to the same pool of potential mates. Without differences in arrival time, there’s no opportunity for migration-based sorting.
The findings suggest something even more interesting: migration routes in Common Terns may not be strongly hard-wired by genetics. Instead, young birds may learn where to go by following their parents—especially their fathers—or by joining migratory flocks. Migration, in other words, may be passed on socially rather than inherited like eye color.
This study reshapes how we think about bird migration, mate choice, and learning—and shows that even epic journeys don’t always shape who birds fall in love with.
