How Might Dialects Developed In Captivity Affect Reintroduction Success For Parrots?
By: 𝐆𝐫𝐫𝐥𝐒𝐜𝐢𝐞𝐧𝐭𝐢𝐬𝐭, Scientist
Tags: Captive Breeding, Conservation, Ornithology, Science, Language Learning

The spectrograms were then grouped based on their similarities to determine whether they could be accurately assigned to their source populations based on their acoustic structure. As Ms Martínez suspected, each of the four populations had its own discrete dialect. Further, she found that contact calls produced by the relict flock at El Yunque were radically different from contact calls produced by all the other populations, and was described as a single repeated syllable, confirming anecdotal reports. It was almost as if the last truly wild flock was speaking a different language entirely.

This contrasts with the contact calls produced by the other flocks of parrots, which are comprised of least two different syllables. Careful analysis revealed that the El Yunque captive, the Río Abajo captive and the Río Abajo free-flying populations all shared at least two call variants, but even still, each population’s contact calls were nevertheless distinctive.

How did these dialects arise?

“The reasons why this happened vary between populations”, Ms Martínez said in email. “To start, the first captive population (the one in El Yunque) was founded by vocally naive parrots.”

“[T]he founders of the first captive population were brought into captivity as eggs and chicks and had not yet learned the wild dialect of their parents. These captive birds had few opportunities to interact with their wild counterparts because there were very few wild Puerto Rican Parrots left at this time and because the captive facility was not located very close to the few remaining wild parrot roosting and foraging sites”, Ms Martínez said in email.

“Since they lacked vocal tutors of their own species, we believe that the first captive parrots may have modeled their vocalizations on Hispaniolan amazons.”

Hispaniolan amazon parrots, Amazona ventralis, are a closely-related species (more here) that is comparatively plentiful on their native Caribbean island of Hispaniola, which is split between the nations of Haiti and the Dominican Republic. These parrots were regularly used as foster parents for iguaca chicks in the early days of the conservation program to help boost the population numbers of iguaca and thus, large numbers of them were kept at the captive breeding facility for this purpose.

A pair of Hispaniolan parrots (Amazona ventralis) in a cage. (Credit: TJ Lin / CC BY-SA 2.0)

“Vocal divergence occurred a second time when the second captive breeding facility was founded in Río Abajo”, Ms Martínez went on in email.

Unlike the facility in El Yunque, this population was founded by adult birds so birds in the Río Abajo flock had the opportunity to learn their calls from members of their own species.

“However, when populations are separated, cultural traits can undergo a process of cultural drift”, Ms Martínez said in email.

Vocal learning, like any learning or copying process, is imperfect so innovations and tiny changes — “errors” — can emerge as one bird learns its calls from another.

“This is one way in which dialects emerge in nature and we believe this is what happened in Río Abajo”, Ms Martínez explained in email. “A similar process likely explains the vocal divergence that occurred when parrots were released into the wild in Río Abajo. Cultural drift again causes the vocalizations to change. For the wild birds in Río Abajo, we believe that the vocal divergence was reinforced by the social interactions that occur outside of captivity. Wild birds model their vocalizations on other wild birds because these birds need to be able to communicate with each other to find food and mates.”

Parrots identify flock members on the basis of their vocalizations, and being a member of a flock comes with a number of other advantages besides finding mates, like evading predators, and working together to find ephemeral food sources.

Tragically, the original dialect spoken by the last 50 or so remaining wild iguaca was forever lost when Hurricane Maria roared across Puerto Rico, destroying the last remnants of the precious relict population living in El Yunque.

Hurricane Maria was a huge setback for the Puerto Rican Parrot Recovery Program

“Losing an entire wild population is an incredible blow to the recovery of any endangered species”, Ms Martínez explained in email. “But that wasn’t even the worst of it.”

Not only did Hurricane Maria completely destroy the wild relict population in El Yunque, but it also caused a 40% decline in the free-flying iguaca population in Río Abajo. Hurricane Maria also caused significant damage to both breeding facilities in Río Abajo and El Yunque and damaged another facility in the Maricao Commonwealth Forest where a third captive population was being prepared for reintroduction by the Recovery Program.

“We’ve been able to make a comeback in recent years though”, Ms Martínez added in email. “Today, the wild population in Río Abajo surpasses that of its pre-Maria numbers. A group of wild parrots was released in El Yunque at the beginning of 2020. The captive breeding facilities are being remodeled and there are plans to re-initiate the release efforts in Maricao Forest as early as next year.”

Are there any plans to teach the captive-bred iguaca their original calls?

“Preserving the original calls at this point seems very unlikely”, Ms Martínez replied in email. “The relict dialect went extinct when hurricane Maria destroyed the relict population in El Yunque and there are no members of that population left that produce this dialect.”

The original contact calls made by the relict flock of iguaca can only be heard in audio and video recordings.

“However, the surviving dialects are still functional to the wild birds as evidenced by how well the wild flock in Río Abajo is doing”, Ms Martínez elaborated in email. “The calls are functional as long as all members of a given population respond to them within the appropriate contexts. That’s why it’s important to give captive birds every opportunity to listen and learn the wild calls of the population that they will be released into.”