Today the archipelago spreads out over 50,000 sq km (19,500 sq mi) of the Pacific Ocean some 1000km (620mi) west of Ecuador and is comprised of thirteen main islands and six smaller ones. This archipelago was formed mainly by the lava forced up from out of the sea by successive underwater volcanic eruptions. Over the millenia, animals and birds have made their way 1000 kilometres over the ocean from South America to these barren islands - either by flying, swimming or floating on randomly formed rafts of vegetation.

Plant seeds and insects arrived stuck to birds wings or in animals stomach contents. Only certain species could survive on the bleak islands, and had to adapt to do so. Charles Darwin was the first to observe how each arriving species had to adapt in order to survive, resulting in characteristics unique to the species on individual islands. The most famous example is "Darwin's finches" - the 13 similar species of finch that probably descended from one original ancestor but which have now unique characteristics to suit its particular environment on different Galapagos islands. Darwin developed his new theories in the seminal The Origin of Species.

There is something fascinating and unique to see in the Galapagos every month in the year, as the yearly wildlife calendar shows, and it can be visited all year round. However, the climate can be broadly divided into two seasons - a hot and wet season and a cooler and drier season.

This page will explain in more detail the seasons and how this affects the wildlife of the islands. We also have a calendar so you can more easily see when Albatrosses will be nesting; sea lion pups playing; whales or blue footed boobies courting.
 

• See the complete Galapagos Calendar