A case of range expansion through the Birds of Panamá guidebooks

Birding PanamaIt seems that the wanderer likes Bocas del Toro:  A case of range expansion through the Birds of Panamá guides

The geographical areas occupied by bird species are not jails, that confine them through history and they can never leave, in fact, in many cases they change through time. The change in a bird’s range can be signaling an important change in their own habitat and also they might have important consequences in the communities of the habitats that are invaded. Nowadays, with technology and increased public interest in birding we have an extraordinary tool to see the changes in range expansion of bird species at almost real time.

I would like to expose a recent case of range expansion that happened in Bocas del Toro, Panamá, just by checking what they say about a particular bird with the different authors through time, in their bird guides of Panama.

The bird that I am going to write about was once described, by Alexander Wetmore in 1968 in his Volume 2 of his The Birds of the Republic of Panama, as “Small, long-tailed parakeet; green above, with a prominent blue band in the wing.” When he described it, it was only found in the “Tropical Zone of western Bocas del Toro. known only from Almirante, and the Río Changuinola”. At that time, the bird was called Aratinga astec astec, and the common name was Aztec Parakeet. Now we call this bird Olive-throated Parakeet and it´s scientific name is Aratinga nana aztec.

As a curiosity, “ the first specimen of this bird taken in Panamá was collected at Farm 3 on Río Changuinola April 15,1927, by Austin Paul Smith. This bird is in the Havemeyer collection in the Peabody Museum at Yale”. There were other specimens collected, all the same year, two males by Rex Benson at Almirante and a female by Hasso von Wedel at Changuinola. With very few historical records, he wrote: “ It is suggestive to note that the four specimens recorded to date (1968) from Panamá were taken between April and October in the same year. Possibly they were wanderers from further north.”

Some years later, Robert Ridgley, in the second edition (1989) of his A Guide to the Birds in Panama with Costa Rica, Nicaragua and Honduras wrote, in the status and distribution section: ”Rare in lowlands of western Bocas del Toro (Almirante-Rio Changuinola area) where known from only six specimens, all taken within the April-October period (four in 1927; one 1961; one in 1963). Perhaps merely an irregular wanderer from Costa Rica; It´s too difficult to see why this species has not settled and even spread eastward along Panama´s Caribbean slope.”

He was very certain that the habitat conditions eastern to it´s range, were suitable for the establishment of this species and he was right, because the presence of Olive-throated Parakeet has been spreading east, passing Chiriquí Grande and, to the Islands, they are found in Isla Colon, Isla Popa and Isla Bastimentos (I have personally seen them on the last two islands).  We can find these changes in 2010 in George R. Angher´s The Birds of Panamá: A Field Guide where he describes the bird as “Common in lowlands of Bocas del Toro”.

In 42 years, the Olive-throated Parakeet has gone from being considered a wanderer to being completely established along the Bocatoranian coast and to being a common bird. We even had a nest at Tranquilo Bay some years ago.  The couple lived with us for more than a year on the grounds of the lodge. This is but only one little example how dynamic the world we live in is.

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