Perhaps mis-named since these evil devices are used during autumn at the peak migration time of passerines through southern Europe.
Whenever I see the locals digging with their "enchadas" out in the countryside it means only one thing - they are looking for the adults and larvae of flying ants which are just emerging from their underground nests. These are used to bait the spring traps (tiny versions of pole or gin traps) which are either laid on the ground under bushes or hung in the bushes themselves. The bird goes for the bait and triggers the trap and has its neck broken. These traps are available in bundles of 50 or 100 at local markets and at government-funded "Co-operativas". It is not illegal to manufacturer these (most are made by the gypsies), to own them or to sell them but it is illegal to use them (how is that for sensible Portuguese bureaucracy?).
(Photo taken by a German resident near Lagos)
One man with a hundred traps can catch several hundred birds a day and, since they are not mutilated like shot birds, they are currently worth €2 per head on the open market as the ingredient of "Empadas de Passarinhos" (Songbird Pie) or simple plucked and grilled and eaten whole (innards and all) - a local delicacy.