This post is the second of two recounting a four-day birding trip my wife and I took to Puerto Rico in May.
I am taking the opportunity to discuss some of the general features of island birds. In the last post, we saw that island species diversity is generally lower in mainland source populations. We also saw that exotic species have an easier time establishing themselves on islands, particularly in disturbed areas.
Today’s column will focus on organisms that are restricted to one or a few islands. These species are called endemics by biogeographers.
It’s easy to see how endemic species can arise. A few individuals of a mainland species make it to an island and, over time, diverge from the mainland species. Sometimes these endemic species are found only on the island where they arose. In other cases, endemic species may disperse to nearby islands.
As an example, the Greater Antillean Grackle is found on the four islands of the Greater Antilles but nowhere else. Similarly, the Lesser Antillean
Bullfinch is found on most of the Lesser Antilles.
Island endemics are restricted to a single island. Puerto Rico has 17 endemic species and those were the main targets of our trip.
Most of the Puerto Rican endemic birds are widespread and common. We had a little time to bird in the afternoon of our arrival on May 9. At Bosque Estatal de Cambalache, our first endemic was a Puerto Rican Lizard-cuckoo, with a lizard in its beak! We found Puerto Rican Bullfinch and Puerto Rican Spindalis (a tanager relative).
Moving to a suburban area in Barcelonata, we hit the jackpot. We saw Puerto Rican Flycatcher, Green Nango (a hummingbird), Puerto Rican Oriole, Adelaide’s Warbler and Puerto Rican Woodpecker.
After a hearty dinner, we stopped at a small tract of forest in Manati where our guide Julio had staked out a Puerto Rican Owl. It responded quickly to a recording, and we got great looks via a headlamp.
It was a great start to our trip. A total of three hours of birding yielded nine of the 17 island endemics.
We started birding early the next day at Bosque Estatal de Rio Abajo. The area quickly yielded three more endemics: Puerto Rican Vireo, Puerto Rico Emerald (a hummingbird) and Puerto Rican Tody. Todies are charming birds. Green above with a red throat and a long, thin bill, these feisty birds are not a whole lot bigger than a hummingbird and fly with the same speed and abandon.
But the primary reason for visiting this site was to find the Puerto Rican Parrot. Only about 100 of these birds exist in the wild with another 450 held in a captive-breeding program. A flock of eight parrots landed near us and I was able to get some nice photos. None of the photographed birds had bands, indicating they had been born in the wild. Good news!
With 13 endemics in the bag, we headed to the southwestern part of the island. A stop at a mountain site produced two target endemics. Elfin Woods Warbler looks like a particularly dark Black-and-white Warbler. The Puerto Rican birds were not recognized as a separate species until 1972.
We also saw my most desired species, the Puerto Rico Tanager. Although it has dull plumage and a weak song, I find it fascinating because of how much it has diverged from its mainland ancestor. DNA evidence supports classifying this bird in its own family, a family of one species.
We got our final two endemic species in the town of Lajas. Yellow-shouldered Blackbird is an Endangered Species with only about 1000 individuals existing. Brood parasitism by Shiny cowbirds is a major threat. We saw about 50 blackbirds in a mangrove thicket.
After dark, we visited the same mangroves and found a Puerto Rican Nightjar to complete a clean sweep of all the Puerto Rican endemics.
You can see a trip report with a list of all the species (some with photos) we saw at: https://ebird.org/tripreport/57209