Tuesday, May 21, 2013 3:24:50 PM
@chalket: It's caused by the Vitali organ in a birds ear. The bird get discomforted by the low air pressure as they go up further in the air, so they tend to hunker down to ride out a storm. The power line is just a comfortable spot to land on. One or two on the line is normal, but when you start seeing seven and up, especially if they are different species, it means the birds are trying to stay low. Admittedly, there are some occasions when it happens just because it is a flock that moves together, like starlings. Or they all just recently arrived from a migration and are tired, but as I said it is "usually a sign," not "proof." Just as dark clouds, thunder, and lightning is also usually a sign, but not proof, there are instances where it does not always rain, as in a dry thunderstorm. But I`m sure most would not plan a trip to the pool that day.