We used to do it as kids because we thought it was hilarious to see them hanging there...till Dad caught us and beat the shit out of us, lol. Now I believe it relates to sales points of narcotics. You just missed out!
Whatever the reason, It's such a cool pic against the blue. Nice one.

Superb capture!

Admired in:
www.ipernity.com/group/tolerance

Meanwhile, swallows disappear from our sky !

To demarcate territories apparently but I have not necessarily the ultimate truth.