While visiting the city of Goya, Argentina, I was surprised to find a monument commemorating the Capistrano-Goya bond made by the swallows that travel each year from one city to the other. Food, reproduction, etc, partially explain the facts, but investigating the issue I can’t find anything meaningful about how or why they develop this behavior.
Any ideas?
It’s not any particular behavior. The swallows return because the missions because they are good nesting places for them (they like the rock walls).
They don’t arrive on any one day – they start arriving days before and keep on arriving days after. People just mark the day, say “Gee, I see a lot of sparrows” and figure they all showed up at once.
I’m having a lot of trouble verifying that it is actually the same swallows that nest in Capistrano that also spend the winter in Goya. A lot of websites state this, but provide no documentation or references. As far as I can tell so far, it’s possible that it is just an unverified legend.
However, many individual birds do return to the exact same site on the wintering grounds in the south year after year, then go back to the same general area to breed in the north where they themselves were hatched. They most likely do this because, having survived the season in one location, they have confirmed that it has adequate resources. There is no point looking for an alternative site if they know where a good one is, so they return there.
Hence even if there is a specific link between Capistrano and Goya, it is not at all remarkable. There are no doubt similar links between many other breeding areas in North America and wintering areas in South America.
In fact, tomorrow is the day the buzzards (supposedly) return to Hinckley, Ohio . . . but just as reliable and predictable as the swallows.