“If you can’t indicate to others that you’re part of their group, you might not gain the benefits of being part of that group,” like joining flocks to evade predators and working together to find food, Wright says.
Growing population
The U.S Fish and Wildlife Service established the first flock of captive-born Puerto Rican parrots in 1973, not far from the secluded territory of the wild resident parrots of El Yunque.
With the wild population so depleted, the scientists got creative. They brought closely related Hispaniolan parrots—which were relatively plentiful in their native countries of Haiti and the Dominican Republic—to Puerto Rico and put them to work as surrogate parents raising Puerto Rican parrot chicks.
The program was successful. By 2006, there were four Puerto Rican parrot populations: a captive flock in El Yunque, one captive and one reintroduced flock in Rio Abajo State Forest, and the remaining original wild flock in El Yunque.
After recording all four populations in the field, Martínez converted more than 800 hours of bird recordings to visual displays called spectrograms. She and her supervisor David Logue, now at the University of Lethbridge in Canada, grouped the calls according to their similarity.
They focused on the two most common calls, the caw and the chi that flock members exchange to keep in contact with each other. The research revealed that captive birds make caw and chi calls with at least two different syllables, while the wild El Yunque birds make entirely different calls, essentially a single syllable on repeat.
Being exposed from an early age to the Hispaniolan parrots’ calls while being separated from elders of their own species likely set the stage for the captive-raised birds to develop new vocalisations, Martínez says.
But the vocal changes didn’t end there. The study also found that each subsequent time the conservationists broke the birds off into new groups, tiny innovations crept into their calls. The captive Rio Abajo group began to sound distinct from its captive parent flock in El Yunque—and after the Rio Abajo captive birds were released into the Rio Abajo forest, the calls changed again.
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These parrots developed new dialects in captivity. Can their wild kin understand them? - National Geographic UK
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