By Susana Madera Galapagos, Ecuador, Jan 22 (EFE).- An inconspicuous and invasive parasitic fly threatens 21 bird species endemic to the Galapagos Islands, including 12 of the 17 finch breeds native to the archipelago’s delicately balanced ecosystem. Philornis downsi, also known as the avian vampire fly, was first detected in the Galapagos in the 1960s …