By Tanisha Heiberg

JOHANNESBURG (Reuters) - The United Nations has banned global trade in wild African Grey Parrots, prized for their ability to imitate human speech, to help counter a decline in numbers caused by trafficking and the loss of forests.

The highly coveted species was placed on the convention's "Appendix I", which prohibits any cross-border movement in the birds or their body parts for commercial purposes.

The decision, made when members of the U.N.'s Convention on International Trade in Endangered Species (CITES) held a secret ballot for the first time ever, came at a two week-long convention in Johannesburg.

"Inclusion in Appendix I is in the best interests of the conservation of the species as it faces both habitat loss and rampant illegal and unsustainable trade for the international pet trade," said vice president and head of the Wildlife Conservation Society delegation Susan Lieberman.

The African Grey Parrot, usually bred in captivity and sold as a pet, was listed on "Appendix II" in 1981, which includes species whose trade must be limited, after concerns over the impact on its numbers.

High levels or deforestation, poor regulation of trade and increased trafficking for the pet industry have led to the decline of the African Grey Parrot, which was once widespread across its natural habitat in central and western Africa.

"During the past 25 years, more than 1.5 million wild African Greys have been taken from their native habitats, making them one of the most traded of all CITES-listed parrots," said U.S. Fish and Wildlife Service Director and head of the U.S. delegation, Dan Ashe.

The African Grey Parrot joins the highly endangered pangolin, a scaly animal with the dubious distinction of being the world's most poached mammal, on the Appendix I list after global trade in it was banned last week.

The CITES conference, which runs until Oct. 5, will also consider competing proposals to loosen or tighten the ivory trade, a bid by Swaziland to sell rhino horn to international buyers, and moves to increase protection for lions, sharks and rays.

(Reporting by Tanisha Heiberg; Editing by Andrew Bolton)