Photos the authority posted online showed the birds tied up and packed into crates.

In an accompanying statement, customs said they found the flamingos "loaded on a truck bearing a Tunisian registration plate" in Jendouba, northwestern Tunisia.

Officials "returned the birds to their natural habitat as part of preserving the species", the statement said.

The greater flamingo, Phoenicopterus roseus, is listed as a threatened species by the International Union for Conservation of Nature.

It is protected under Tunisian law, according to Hichem Azafzaf, an environmentalist and coordinator at BirdLife Tunisia.

Alongside climate-driven threats, the species faces "illegal hunting and smuggling", Azafzaf told AFP.

The bird's migratory route spans West Africa, Europe and parts of Asia via the Mediterranean Sea.

Drought and rising temperatures have dried up lakes and wetlands where it nests, including Tunisia's heavily polluted Sebkhet Sejoumi near the capital.

In eastern Algeria last year, volunteers rescued about 300 flamingo chicks after a salt lake where they hatched dried up.