Andes

In the fourth programme, the viewer is taken on a journey along the Andes, the spine of the continent. In the northern tropics, spectacled bears feed on bromeliads in the cloud forests and on the puya flower spikes in the alpine grasslands of the Páramo. At these altitudes hummingbirds find it difficult to hover, so those such as the Andean hillstar perch on flowers as they drink the nectar. The Andes are a young range in geological terms, and volcanic activity is still present. The mountain-building forces have thrust up the altiplano, a high, dry desert with geyser fields, caustic lakes and little vegetation. Vicuñas and vizcachas have adapted to the thin air and large daily temperature variation. Despite the treeless environment, even woodpeckers are found here; the Andean flicker nests underground. The geysers and hot springs never freeze so flamingos here can stay year-round, but those on the salt lakes must migrate to lower altitudes to escape the winter. Late-hatching chicks can be trapped by the ice before they can fly. The final part of the programme features Patagonia, where the mountains are lower but closer to Antarctica. The ice fields are so vast they generate their own glaciers and weather systems, blasting the remnants of ancient volcanoes with cold winds. Guanacos, gray foxes and pumas are filmed in both winter and summer. Birds featured include spring migrants buff-necked ibises and great grebes, while the resident Andean condors are big enough to see foxes off a carcass.