Whistler cork oak, Cork oak tree in Águas de Moura, Palmela, Portugal

The Sobreiro Monumental, or Whistler Tree, stands near Águas de Moura at about 16.2 m tall with a trunk circumference of 4.15 m at breast height. Its thick, gnarled trunk supports a broad crown of heavy limbs, and the bark shows the scars of more than 20 cork harvests since 1820.

The tree was planted in 1783 and received protected status as a Tree of Public Interest in 1988. These designations mark a long history of recognition for this special specimen.

The tree's name comes from the whistling of birds that land on its branches. Since 1820 it has been harvested more than 20 times; in 1991 alone it yielded over 1,200 kg of cork, enough for more than 100,000 stoppers.

The tree stands in the Herdade do Chaparral cork oak estate near Águas de Moura, in the municipality of Palmela, and is reached by local roads through the estate. It is a single isolated specimen in open cork oak woodland, so there is no marked trail or visitor structure; visitors approach it on foot from the access road. The surrounding groves were the object of an illegal urban expansion around 2000, which led to the 2001 legal reform protecting cork oaks.

The tree earned its name from the birds that nest in its branches and fill the air with their calls. This natural bird diversity makes every visit an acoustic experience.