Synopsis and videos of episode 4 of the David Tennant narrated Earthflight

Episode four of the David Tennant narrated Earthflight premieres on both BBC One and BBC HD tonight at 8pm.

The synopsis of the episode is:

"The documentary series gives a bird's-eye view of South America, as condors soar along the Andes, scarlet macaws explore the heart of the Amazon and hummingbirds and vultures see the continent's greatest sights. It is a journey that includes Machu Picchu, the Nasca Lines and the cities of Rio de Janeiro and Santiago.

In Patagonia, giant petrels shadow killer whales as they hunt seals by stranding their huge bodies on the beach. At Iguassu Falls, dusky swifts dive through the cascades to huddle in communal roosts while hummingbirds bathe below. In a secret Andean location, condors soar in flocks over 40-strong and scavenge on casualties from herds of fighting guanacos.

Elsewhere, a mother condor gently pushes her youngster to the edge of a 200-metre cliff, as flight school begins. Deep in the Amazon, macaws seek medicinal clay. They are joined by a host of secretive jungle animals, including spider monkeys and tapirs, all after the same remedy.

In Peru, condors soar over fighting sealions waiting for casualities and on a mass exodus north, birds converge on the Panama Canal. In Costa Rica, black vultures descend on turtles as they lay their eggs in the sand and pick off the eggs that ping-pong through the air."

John Downer productions have added three preview clips for this episode of Earthflight about South America. The clips are titled Condor's Birds Eye View of the Andes, Condor Flight School and Scarlet Macaws Feed on Clay Licks. All of them feature David Tennant's narration.

Please see the Earthflight section of DavidTennantOnTwitter.com for more info about this programme.