INNOVATION AT THE HOE

This morning at Samphire Hoe the house martins that normally collect mud for nest building from the puddles in the car parks were seen collecting mud and sea weed from the exposed rocks as the tide dropped.
They build their nests under the many overhangs on the cliff face,no doubt before man provided houses this was the norm,perhaps in previous times collecting materials this way was also normal who knows whether this is a new action born out of necessity or a long forgotten art hiddden in the memory banks. Has anyone  seen this behaviour elsewhere?