Wild Barcelona: Bountiful butterflies

As grass goes to seed, the slopes below Sant Pere Màrtir are turning pale gold, the colour of summer. The vivid yellow flowers of Spanish broom that illuminate Collserola in May are nearly extinguished, and now it’s time for scabious. Its frothy purple-pink blooms are everywhere, on waist-high stems, leaves hardly to be seen, and usually with a butterfly attached.

The most abundant butterflies in Collserola are among the most beautiful, such as the Iberian Marbled White, delicately shaded in charcoal. And the diminutive Common Blue, whose males spread their wings with a violet shimmer.

Down in the valley bottom, rabbits rustle among this year’s crop of fennel, which is already two metres high. A whistle resonates. It’s mysterious how a bird as large and scorchingly yellow as the Golden oriole somehow manages to remain invisible. Without its characteristic calls, which starlings love to mimic, we might never notice that this species comes to breed here every year. Another summer visitor is the Woodchat shrike, a butcher bird with a chestnut crown that impales its prey on spines. The dried twigs of broom are sharp enough to serve as a larder or to help crack open a stolen egg.

Near the top of the ridge, spectacular Illyrian thistles have shot up like spiny candelabra. Hummingbird hawk moths zip among their electric purple flower heads. Sometimes people armed with gloves and knives come to cut the stems and strip them of thorns. If the Devil grows Illyrian thistles in his garden—in Castilian they’re called Cardo del Demonio—it’s because both stems and flower heads are edible, apparently similar to artichokes.

As evening falls, the searing sound of wings fills the air, as common and alpine swifts swoop for insects. At twilight they drop down to the city below, to the traffic-filled canyons where they nest.