Caribbean Parrots Are Remnants Of A Millennial Scale Extinction

A new study combines fossil and archaeological records with DNA samples to trace the history of Amazona parrots in the Caribbean from the Pleistocene through the Holocene

© Copyright by GrrlScientist | hosted by Forbes | LinkTr.ee

When Christopher Columbus arrived on the shores of Puerto Rico in 1492, he wrote, almost poetically, in his Diario about the clouds of parrots whose bright wings obscured the sun. Tragically, those clouds of parrots are long gone. In fact, more than half of all known parrot species in the Caribbean are extinct. What happened? How did the wild parrots of the Caribbean go from “obscuring the sun” to almost nonexistent today?

Humans happened.

Before we do a deeper dive into this study, I think it is important to show you a map of the region because, if you are like me, you’re gonna get confused by all the geographic chaos.

Several islands that you should make a mental note of on this map are Cuba, Hispaniola, and Puerto Rico. Also note that the Bahamas, which are actually in the north Atlantic Ocean, are not part of the Caribbean, but they figure in this story, too. This map describes the geographic home of roughly 24 known species of parrots, although a significant number of them are now extinct. Currently, there are 9 described species of Amazona parrots endemic to the region.

Similar to detectives who arrive at a crime scene after the events happened — sometimes long afterwards — an American team of researchers are working to better understand how people impacted the diversity and geographic distributions of parrot species throughout the Caribbean. Because humans arrived on most islands relatively recently, islands (in general) can serve as case studies for anthropogenic impacts on ecosystems and on species. Consequently, this study is part of a larger ongoing effort to better understand why parrots, especially those living on islands, are amongst the most endangered groups of birds alive today, with 28% of all species under threat with extinction.

This study reports detailed examinations of fossil bones and archaeological specimens and integrates those findings with comparisons of DNA sequences from ancient and modern parrot species endemic to the Caribbean. The goal of this study was to identify historical geographic distributions and diversity of the Cuban parrot, Amazona leucocephala, and the Hispaniolan parrot, A. ventralis, and place this information into the larger context of extant parrot diversity.

Let’s start with earlier times. We know that the two study parrot species diversified during the most recent Ice Age, which lasted from roughly 2.58 million to 11,700 years ago. We also know that both parrots originally had a larger geographic range and a more diverse gene pool than today. This research documented the complex history of local extirpations and translocations for these two parrots that began with Indigenous (Amerindian) occupation of the islands and continued with European colonization. Such dynamics are probably typical for the parrots of the region. Understanding the effects of these long-term human-parrot dynamics is critical for Caribbean ecosystem restoration today.

“People have always been obsessed with parrots,” lead author of the study, forensic ornithologist Jessica Oswald, a senior biologist with the U.S. Fish and Wildlife Service Forensics Lab, said in a press release. Dr Oswald’s expertise is identifying how changes in diversity and species distributions across temporal and spatial scales are tied to the extinction of birds and to the phylogenetic relationships amongst lost and living species.

“Indigenous peoples have moved parrots across continents and between islands for thousands of years,” Dr Oswalt explained. “Later, European colonists continued that practice, and we’re still moving them around today.”

Thanks to centuries of trade, it is difficult to know how Caribbean parrots got to where they are today. For example, we know that half of the 24 parrot species living in the Caribbean were introduced from other areas, but currently, we don’t know if the native parrots evolved on the islands where they are found or if they were moved there by people. But their popularity amongst early humans means that parrot bones are sometimes found in archaeological sites. Their bones have been recovered from refuse piles—called middens—alongside shells, fish bones and other scraps from ancient meals.

“There are records of parrots being kept in homes, where they were valued for their feathers and, in some cases, potentially, as a source of food,” said senior author archaeologist Michelle LeFebvre, assistant curator of South Florida archaeology and ethnography at the Florida Museum of Natural History. Most of Dr LeFebvre’s research is cross-disciplinary in nature, focused upon the synergy of culture and biology, and investigates long-term trends in human procurement, consumption, and use of natural resources as a way to better understand and model relationships between humans and their environment through time.

Fossil hunters may be surprised to learn that, despite their fragile bones, parrots have a surprisingly good fossil record in the Caribbean, compared with other tropical regions. But fossil specimens are rarely found intact. It’s often the case that these bones are broken or isolated, strewn across the landscape, thereby making it impossible to identify species.

Thus, ancient DNA data can be critically important for identifying species from these fragmented bones.

“For me, the single most satisfying thing about this project is we can use fossils in ways that weren’t even imaginable when they came out of the ground,” said paleontologist and ornithologist David Steadman, who now is a retired curator of ornithology at the Florida Museum, and who is an expert on the biogeography and extinctions of birds throughout the tropical Pacific Ocean.

Dr Oswald appears to be one of the vanguard in this ancient DNA effort. As a graduate student and postdoctoral associate at the Florida Museum, she successfully sequenced DNA from an extinct Caribbean bird of prey whose bones had been preserved for 2,500 years in a “blue hole” — a deep oxygen-free water-filled sinkhole (ref). Later, using the same methodologies to study a different set of b0nes, Dr Oswald made the surprising discovery that the closest relatives to an extinct flightless Caribbean cave-rail were ground-dwelling birds in Africa and New Zealand (ref). This cave-rail’s extinction reminds us that being plump and flightless is a bad survival strategy for birds after human settlers arrive on your island.

For this study, Dr Oswald and collaborators focused on two Amazona species from which they were able to obtain usable ancient DNA samples.

Of the two study birds, the Cuban parrot, also known as the rose-throated parrot, are the most widespread in the Caribbean Archipelago at this time, with a few isolated populations on Cuba and several more populations living on other islands in the Bahamas and in the Turks and Caicos. Cuban parrots one of the only native parrots in this region that are not in imminent danger of extinction.

The other study parrot, the Hispaniolan parrot, is limited to Hispaniola, which is comprised of the Dominican Republic and Haiti. This parrot’s population is declining, so it is listed as vulnerable to extinction by the International Union for Conservation of Nature’s Red List.

The data analysis suggested that Amazona parrots were more diverse and abundant during the Pleistocene epoch than at present. Between 6,000 and 1,000 years ago, the data show a significant loss of parrot diversity and geographic ranges occurred, including local extirpation of a population of Cuban parrots on the Turks and Caicos Islands.

Most of the fossil fragments examined in this study that were unearthed outside of Hispaniola and Puerto Rico were originally thought to be from Cuban parrots. But the ancient DNA data revealed a surprise: fossils from paleontological sites throughout the Bahamas were actually from Hispaniolan parrots, indicating this species had a much larger range throughout the Bahamas before humans arrived. Later, the range of the Hispaniolan parrot dramatically contracted to the island of Hispaniola, where the species is now endemic. Additionally, the study found that the Hispaniolan parrot may have been introduced to a number of other islands by people, including Grand Turk and Montserrat, but has since been extinguished from those islands.

“One of the striking things about this study is the discovery of what could be considered ‘dark extinctions’,” Dr LeFebvre pointed out.

Dark extinction, or anonymous extinction, refers to the extinction of a species before it is discovered and named. This phenomenon is widely construed as a significant part of species loss in the ‘pre-taxonomic period’ (approximately 1500–1800 CE) and, to some extent, in the ‘taxonomic period’ (approximately 1800–present).

“We’re learning about diversity we didn’t even know existed until we took a closer look at museum specimens,” Dr LeFebvre said.

Taking this study’s findings into account, what should conservationists consider to be the legitimate distribution of parrots throughout the Caribbean?

“We have to think about what we consider to be natural,” Dr Oswalt replied. “People have been altering the natural world for thousands of years, and species that we think are endemic to certain areas might be the product of recent range loss due to humans.”

According to the authors, insights into past diversity gathered from a variety of disciplines may help guide future conservation efforts, starting with understanding where particular species once thrived. Additionally, studies of island-dwelling parrots in other parts of the world — particularly Oceania — could also provide useful comparisons and insights.

“It takes paleontologists, archaeologists, evolutionary biologists and museum scientists all working together to really understand the long-term role of humans on diversity change.”

Source:

Jessica A. Oswald, Brian Tilston Smith, Julie M. Allen, Robert P. Guralnick, David W. Steadman and Michelle J. LeFebvre (2023). Changes in parrot diversity after human arrival to the Caribbean, Proceedings of the National Academy of Sciences 120(41):e2301128120 | doi:10.1073/pnas.2301128120

---

SHA-256: 9ab94921e06b203a216cb219d873f92ea4083642075e2e0be632939cd42949aa

Socials: Bluesky | CounterSocial | LinkedIn | Mastodon | MeWe | Post.News | Spoutible | SubStack | Tribel | Tumblr | Twitter

Denial of responsibility! TechCodex is an automatic aggregator of the all world’s media. In each content, the hyperlink to the primary source is specified. All trademarks belong to their rightful owners, and all materials to their authors. For any complaint, please reach us at – [email protected]. We will take necessary action within 24 hours.