Diet mostly insects and other small arthropods; also seeds, fruit, buds, and sometimes flower nectar. This includes cracking hard Opuntia seeds, extracting seeds from Opuntia fruit and eating the arils… The Ground Finches eat ticks which they remove with their crushing beaks from Tortoises , Land Iguanas and Marine Iguanas and they kick eggs into rocks to feed upon their contents. [3] Geospiza is a genus of bird in the family Thraupidae.All species in the genus are endemic to … Wiki User January 11, 2013 6:24AM. Darwin’s Finches vary by what they eat, some eat seeds and others eat insects. If you know the answer to this question, please register to join our limited beta program and start the conversation right now! Why does geospiza fortis eat seed? it mostly eats seeds. What do geospiza fortis eat? Finches with the larger beaks to open seeds (such as the Geospiza magnirostris), and smaller ones to eat insects (as Geospiza parvula, above), evolved to fill the environmental niches afforded on the islands. The medium ground finch feeds primarily on seeds, although it is also known to eat flowers, buds, and young leaves, and the occasional insect. During the dry season when competition for food is most intense, it exercises different skills to obtain four main food items. Asked in Taxonomy What is the taxonomic classification of a … They generally feed on seeds, arthropods and, various parts of the prickly pear cactus. Related Questions. Answer. We need you to answer this question! Feeds on prickly-pear cactus pulp, flowers, fruits and insects. It forages either on the ground or in low vegetation. Those species without needed variations died out.