Birds migrate at night in loose flocks

Birds migrate at night. Bird tend to flock together.

These two disseparate facts have been recently weaved together to suggest that birds migrate at night in flocks. What I find interesting here is the suggestion that these flock are “loose”–not the tight configurations visible in the preceding video of starlings flying in a flock–birds may be migrating in groups that are as much as 200 meters apart from each other. As the lead researcher, Ronald Larkin, suggests birds flying in the same direction at one point in time is not the same as birds travelling together over long distances:

“Even back in the 1970s it hit me that you can have two birds flying absolutely parallel in the same direction and at the same height, but they can be flying at such a different speed that one of them gains on the other and they’re just, you know, automobiles passing on the expressway,” he said. “They’re simply taking the same route and not keeping together.”

What Larkin has shown through a magic elixer of radar and statistics is that migrating birds tracked were actively travelling together: same speed, same altitude, same direction. Just much further apart then we had ever imagined before.

For me, this finding brings up the obvious question: how? I know I’ve stood outside during spring and fall migration and heard the whisper thin call of migrating passerines, so perhaps they stay in contact via vocalizations. But that’s just conjecture on my part.

And I have to share Larkin’s sense-of-wonder with this phenomenon:

“To me, that’s the marvelous thing – that they’re flying in social groups in the middle of the night in the middle of the air, over territory most of them have never been over before.”

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