More than sixty per cent of Peru is Amazonian, and almost no tourist itinerary includes it. That is a shame, because a short flight is enough to change countries completely.
Three ways in
Puerto Maldonado, in Madre de Dios, is the most practical option if you are coming from Cusco: forty minutes by air and about the same again by boat up the Tambopata or Madre de Dios river to the lodge. The Tambopata National Reserve holds extraordinary biodiversity, and its clay licks — walls of clay where hundreds of macaws and parrots gather at dawn to eat minerals — are among the most reliable natural spectacles on the continent. Three nights covers a good deal: a night walk, Lake Sandoval with its giant otters, and a canopy observation tower.
Iquitos is another matter entirely: the largest city on earth with no road connection, with rubber-boom mansions faced in Portuguese tiles and the floating district of Belén. From there you reach the Pacaya Samiria Reserve, the country's largest flooded forest, usually on cruises of three to seven days. Pink river dolphins are more likely here.
Manu National Park is the hardest and the most complete, because it descends from three thousand metres of cloud forest to the lowland plain, crossing every ecological tier on the way. It needs at least a week and much of the journey is overland. It is the best choice for anyone travelling specifically to watch birds.
What to bring, and when to go
DEET repellent, light long-sleeved clothing, a head torch, a light waterproof and binoculars. Rubber boots are usually lent by the lodge. Yellow fever vaccination is recommended in advance, and in some areas malaria precautions are worth discussing with a doctor.
The rainy season, December to March, raises the rivers and allows you to navigate between flooded trees; the dry season, May to September, concentrates wildlife along the banks and makes walking more comfortable. Both work — there is no bad one.
One warning
Ayahuasca ceremonies are offered around Iquitos and Puerto Maldonado with no oversight whatsoever, and there have been serious incidents. If it interests you, research the centre and whoever runs the session very carefully, and do not decide on the street on the day.