The Puerto Rican Emerald (Chlorostilbon maugaeus) is a hummingbird species endemic to the island of Puerto Rico. With a total body length of about 9-10 cm (3.5-4 in) and a weight of 2-3 grams (0.07-0.1 oz), it is one of the smallest birds in the world. This tiny hummingbird gets its name from its vibrant emerald green plumage on the head, back, and parts of the wings and tail. The belly is white with green spots on the sides. The long needle-like bill is black, adapted for feeding on nectar from flowers.
The Puerto Rican Emerald is one of two hummingbird species found only in Puerto Rico, the other being the Antillean Mango. It is most closely related to the Green-throated Carib, which is found on nearby Caribbean islands. The Puerto Rican Emerald inhabits a wide range of habitats on the island, including forests, woodlands, plantations, gardens, and mangroves. However, it prefers edges and openings in forests with flowering plants and tropical flowers.
Some key plants the emerald hummingbird feeds on include flowers from banana, Heliconia, ginger, coral bean, and epiphyte plants like bromeliads. To feed, the hummingbird hovers in front of a flower, extending its long tongue into the flower to lap up nectar. It also catches small insects like gnats, fruit flies, and spiders to obtain protein. The slender curved bill allows it to reach nectar at the base of long tubular flowers.
The breeding season for Puerto Rican emeralds runs from March to June. The tiny cup-shaped nest is constructed using plant down, spider webs, lichens, and moss. It is well camouflaged, located on a tree branch, fern, or cactus, and blends in with the surroundings. The female emerald lays two pea-sized white eggs and incubates them for 14-23 days. Both parents feed the hatchlings with regurgitated food. The young birds fledge in about 20-26 days.
Puerto Rican emeralds are continuously active during the day as they feed on small amounts of nectar every 10-15 minutes. They aggressively defend their feeding territories from intruders, even chasing away much larger birds. Their wings beat up to 75 times per second, producing the characteristic humming sound. At night they enter a state of torpor to conserve energy. Their slender bodies have very high metabolisms, so they must feed frequently to raise their body temperature and power their rapid wing beats.
This species faces a number of threats across its limited habitat. Development, urbanization, logging, agriculture, invasive species, and climate change all pressure the emerald hummingbird’s survival. It has lost significant forest habitat over the last century. Herbicides also reduce available flowers and nectar food sources. Hurricane damage degrades and fragments its niche. Additional threats come from competition with honeybees for nectar sources and nesting predation.
Conservation efforts are needed to preserve remaining forests and flowering plants that provide food and shelter. Ecotourism can potentially support habitat protection. Captive breeding programs may help bolster emerald hummingbird populations. Safeguarding critical corridors between isolated habitat zones can allow for better dispersal and gene flow. Further studies of range, diet, breeding, and ecological needs are required for effective management strategies. The Puerto Rican Emerald serves as an important pollinator and seed disperser, helping maintain healthy rainforest ecosystems. Protecting this unique Caribbean island hummingbird is critical for biodiversity conservation far beyond Puerto Rico.