28 March, 2024
By Alexander Trifunovic
An adult Woodpecker Finch (Camarhynchus pallidus) with a fledgling. Photo by Julien Renoult, CC BY 4.0, via Wikimedia Commons.
Islands act as drivers for adaptive radiation and the evolution of new species, and this phenomenon can be observed on the world-renowned Galapagos Islands off the western coast of South America. Most famous of the volcanic archipelago’s birds are Darwin’s finches (subfamily Geospizinae), comprising five genera within the megadiverse family of Neotropical Tanagers (Thraupidae). Each species evolved their own adaptations for a particular niche in the island chain’s dynamic and harsh climate. The Woodpecker Finch (Camarhynchus pallidus) is visually plain and unassuming but makes up for it with its adaptable lifestyle and unique use of tools. These birds use their long, sharp bills to peck open branches to access wood-boring insect larvae, and they also utilize twigs or cactus spines to skewer and extract their prey. Woodpecker Finches are found across most of the major Galapagos Islands and occur in a variety of arid and lush habitats. Their unique tool-using behavior is not seen in all individuals of this species, nor in all habitats. Birds occurring in the humid Scalesia forest forage mainly by gleaning arthropods from epiphytes and leaves and do not use tools.
Humid Scalesia cloud forest in the Cerro Pajas Crater on Floreana Island. With some of the only trees in the sunflower family Asteraceae, this plant genus as unique as the island chain’s birds with its own adaptive radiation. Photo by Ackatis, CC BY 4.0, via Wikimedia Commons.
Woodpecker Finches in the arid zone regularly use tools for prey extraction, and during the dry season, this foraging strategy makes up 50% of foraging time. Some prey that was particularly valuable, such as spiders and orthopterans, could only be accessed using tools. This suggests that tool use in Woodpecker Finches evolved as a way of accessing valuable prey in an arid environment where arthropods are less abundant and often concealed. Research shows that tool use in Woodpecker Finches may not be associated with high cognition, at least not as we currently understand it. Instead, their tool use is a combination of genetic predisposition, specific stimuli during juvenile development, and individual learning. Unlike corvids or primates, Woodpecker Finches are primarily solitary, so it makes sense that their ability to wield tools would be ingrained rather than socially learned.
Prickly pear cactus and brush in the Galapagos arid zone. In this habitat, Woodpecker Finches utilize tools to acquire prey. Photo by Harvey Barrison from Massapequa, NY, USA, CC BY-SA 2.0, via Wikimedia Commons.