Two and half million years ago a few small birds landed on an island somewhere in the region of the Galapagos hotspot. Santa Cruz was perhaps not even born at that time but San Cristobal might have already developed plant life capable of supporting the feet of a perching bird and, moreover, providing a bite to eat. How a finch would survive the 1,000 km or more journey from continental America is not easy to know, yet behind these birds, as they were carried westward by wings or weather, was an event so unique that it was capable of changing the world’s climate. It was the closing of the Central American Seaway as the agents of geographic change, the plates of tectonic theory, tugged, pushed, and jostled with each other on massive scales. It is possible that the atmospheric turbulence of those times pushed the finches west. Yet great events were not to end. As the Seaway closed the Quaternary ice age set in, pulsing alternate waves of warmth and ice across the planet in cycles which at first lasted 41,000 and later 100,000 years.
We live in an interglacial period of that ice age. As each glacial period deepened and more water was locked up in the ice sheets, the sea levels dropped worldwide. The tiny remote islands of the then unnamed Galapagos lengthened their low lands toward each other, sometimes coalescing to offer pathways across the seas. A pathway a small bird could pass along, without knowledge that, in time, as the sea level rose during the next interglacial, its future generations would be living on a different island from which it set out. By then new islands were growing over the hotspot, magma chambers pumping up fluid lava to flood over the sea bed and finally to burst above the surface, settling and hardening to form new land. The birds continued to move to and fro between islands. By chance the small birds might find themselves on arid land and simply die. At other times they face the possibilities of new adaptations amongst the trees, the coastal life, and in symbiotic relations with other vertebrates. Ever adventurous in a new habitat, they developed into at least 14 separate species, the most remarkable extant example of adaptive radiation on earth.
A million years ago, to the north of the Galapagos hotspot in an area known as the Galapagos Spreading Center (the most active seismic area in the Galapagos region), great faults developed, resulting in an outpouring of lava which gave rise to Wolf Island. This island, along with the neighboring island of Darwin some 145 km away, is the most remote and northerly of the Archipelago. Existing in a more tropical climate, they serve as a rendezvous for whale sharks and another elasmobranch, the hammerhead shark, which circumnavigates its vertical shoreline.
The rocky, crumbling landscape of this eroding volcano is unique for a particular species of finch. In the cold season the vegetation is bereft of fruits and flowers but the sea is abundantly productive with high protein fish. There is only one way in which the small, sharp-billed finches can get at this essential food source…come back next week to read how they do it…
Written by Godfrey Merlen