by itself , the egg disappears .
p. downsi kills huge numbers of baby birds among darwin ’s finches and other land birds .
now , research suggests that at least some of darwin ’s famous finches might soon be driven to extinction by parasitic flies introduced to them by humans in the 1960s .
while adult p. downsi flies are not themselves parasitic , they lay their eggs in bird nests .
the flies can be found on every island in the galápagos .
some researchers have even speculated that the striking color helps mother birds to find their own eggs .
for now , however , the case of the mysteriously blue robin ’s egg has yet to be cracked .
during charles darwin ’s journey to the galápagos in the 1830s , he noted the existence of “ a curious group of finches ” found only on the islands .
a paper published this week in the journal of applied ecology blames the parasitic nest fly philornis downsi for the threat to geospitza fortis , also known as the medium ground finch .