Habitat and Distribution
The species was once commonly found in the coastal forests of the archipelago of Puerto Rico but during the early 20th century these forests were destroyed to allow for the development of sugarcane plantations. After the decline of the sugar industry after the 1930s the coastal areas were developed for housing. As a result, the species is now limited to three areas: the islands of Mona and Monito, where a subspecies developed (A. g. xmonensis); the Roosevelt Roads Naval Station area in eastern Puerto Rico; and the southern Puerto Rican dry forests and mangroves. Although all three locations are considered coastal subtropical dry forests, the species has been observed as far inland as the mountain town of Lares and in subtropical wet forests during the non-breeding season. The species has also been observed at the Cabo Rojo National Wildlife Refuge. The destruction of habitat and brood parasitism by the Shiny Cowbird (Molothrus bonariensis) led to a drastic population decline during the mid-70s to early 80s. In 1976, the population of the nominate form was estimated at 2000 individuals but in 1982 the population estimate dropped to 300 individuals. Conservation efforts have increased the population to 1250 pairs.
In 1976 Post and Wiley estimated the Mona subspecies population at 200 individuals. Subsequent roost counts and studies from 1981 to 1995 estimated the population at anywhere between 220 to 400 individuals. Studies performed in the island of Monito, located 5 km (3.1 mi) northwest of Mona, revealed an average of 25 individuals with breeding also being observed. The studies also revealed that birds traveled from the west coast of Mona to Monito.
Yellow-shouldered Blackbirds are non-migratory birds, but a portion of the population of the nominate form moves from coastal areas to inland areas during the non-breeding season to feed.
Read more about this topic: Yellow-shouldered Blackbird
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