Country diary: Here, at least, martins and swallows are abundant | Mark Cocker

Castro Verde, Portugal: In contrast to my Derbyshire home town, the numbers are vast and their blue-and-white flight lines gloriousJust off the main square in this southern Alentejo town is a post office of semicircular shape. It's an attractive structure somewhat resembling a tiered wedding cake, and at the point where its curved front meets the first flat, tiled roof is a series of protruding brick supports. Into the 10 alcoves framed by these and spanning no more than six metres of the whole facade, house martins have inserted roughly 200 of their little mud-brick houses.Scores of the chattering labourers fly in and out of their works to present to any passing observer a glorious, ever-changing weave of blue-and-white flight lines. We were far from the only people to stop and admire this beautiful, kinetic sculpture, yet it's also the most densely packed subcolony of this species I've seen in my life. Continue reading...