The Purple-bibbed Whitetip (Selasphorus heloisae) is a recently discovered species of hummingbird found in the tropical mountains of Costa Rica and Panama. This striking bird has vibrant plumage with a purple bib on the throat and white tips on the tail feathers, giving rise to its common name.
Introduction
The Purple-bibbed Whitetip is a mid-sized hummingbird measuring about 10-12 cm in length and weighing 5-7 grams. Like all hummingbirds, the species displays sexual dimorphism with the male having the most vibrant plumage. The male has an iridescent purple throat bib, a metallic green crown and back, a rufous belly, and conspicuous white tips on the outer tail feathers. The female has a lighter belly and lacks the bold purple bib and white tail tips. Both sexes have a slender curved bill adapted for accessing nectar from flowers.
The species was first documented in 1996 in the Talamanca Mountains of Costa Rica but went undescribed as a unique species until 2004. Ornithologists gave it the scientific name of Selasphorus heloisae. The Purple-bibbed Whitetip is closely related to other Selasphorus hummingbirds found farther north such as the Rufous and Allen’s Hummingbird. There are estimated to be only around 1000-2500 individuals remaining in the wild, confined to a small geographic range. Habitat loss is the main threat facing this endangered species.
Physical Description
As mentioned above, the male Purple-bibbed Whitetip has unmistakable plumage. The throat bib shimmers a bright amethyst purple in the sunlight. This bib along with the metallic emerald crown serve to attract females during courtship displays. When the tail feathers spread, the white tips are visible on the outer three pairs, a unique trait among Selasphorus hummingbirds. The belly is a rufous-cinnamon shade. The bill of both sexes is needle thin, slightly downcurved, and around 2 cm in length.
Females lack the bib and white tips, having a pale throat and belly and rufous washed tail feathers. Immature birds resemble adult females until obtaining their mature plumage in the second year. In general, the species exhibits a slender, streamlined body shape adapted for specialized nectar feeding. Their petite size allows maneuverability while hovering at flowers. Iridescent plumage colors are produced by the physical structure of the feathers, with pigments playing a lesser role.
Range and Habitat
The Purple-bibbed Whitetip occupies a restricted range in the mountainous Talamanca region straddling the border between Costa Rica and western Panama. The species seems to be confined to elevations between 2400-3300 meters above sea level. Few intact forests remain at this altitude, leading to the fragmented distribution.
This hummingbird inhabits cloud forests and elfin forests characterized by trees and vegetation stunted by humidity and cooler temperatures at higher elevations. It also occurs in secondary forest habitats with plenty of flowering plants. Key plants in these mountain ecosystems include oaks, magnolias, and epiphytic plants such as orchids and bromeliads. The flowers of these plants provide nectar sources for the hummingbird.
Feeding Habits
Like all hummingbirds, the Purple-bibbed Whitetip feeds on floral nectar and tiny insects and spiders. The primary food source is nectar, which provides carbohydrates. The long bill allows the birds to insert their tongues into flowers to drink the nectar. Preferred flowers are those with an elongated shape and abundant nectar content. These include flowering plants in the Rubiaceae, Ericaceae, and Gesneriaceae families.
Small arthropods including insects and spiders constitute the other portion of the diet. These provide essential proteins. The hummingbird gleans the tiny insects from foliage or catches them in flight. Common prey includes mosquitoes, fruit flies, gnats, moth larvae, spiders, and aphids.
Foraging takes places primarily within forest understory and edges along with adjacent open meadows. The species appears to have a specialized role as a trapliner, regularly visiting localized nectar sources along established routes. This may minimize energy expenditure. Peak foraging occurs in the morning and afternoon, with rest periods in between.
Unique Adaptations
Hummingbirds have evolved remarkable physiological and morphological adaptations to facilitate a nectar-feeding lifestyle. The Purple-bibbed Whitetip shares these traits. A rapid heartbeat and breathing rate allow high metabolism needed to power hovering flight. The wings beat around 50 times per second, allowing precise maneuverability.
Digestive enzymes and a grooved tongue tip allow hummingbirds to drink nectar efficiently. Excess water is excreted as dilute urine to prevent overload. The bill length matches closely with preferred flower shapes. Body feathers trap air for insulation against heat loss in cool mountain conditions.
Like other hummingbirds, the species can enter torpor, a short-term hibernation to conserve energy such as overnight or when food is scarce. The Purple-bibbed Whitetip appears specifically adapted to take advantage of the cooler, drier conditions found at higher elevations in its range.
Reproduction and Life Cycle
The breeding season for the Purple-bibbed Whitetip extends from February to June corresponding to the dry season in its tropical range. Courtship displays feature males flying in loops and dives to show off plumage for potential mates. If receptive, the female will allow the male to approach closely.
The female constructs a small cup-shaped nest out of plant down and spider webs on a low branch or fern frond. She incubates the two tiny white eggs for about 16 days. The eggs hatch asynchronously so one chick might be larger than the other. The chicks fledge in around 20-25 days, after which the female continues to feed them for a couple weeks.
Predators of eggs and young include tree rats and snakes. Adults may fall prey to Accipiter hawks. Lifespan in the wild is likely 3-5 years. The species exhibits site loyalty, returning to the same breeding and foraging grounds year after year.
Conservation Status and Threats
The restricted range and population size has led the IUCN to classify the Purple-bibbed Whitetip as endangered. Habitat loss poses the greatest threat. An estimated 90% of original habitat has been logged or converted to agriculture. This leaves only fragmented pockets of suitable forest. Climate change could impact cloud forest ecosystems.
Introduced honeybees may compete for nectar sources and spreads of diseases. Nest predation and collisions with windows or cars also contribute to mortality. However, ecotourism focused on birdwatching provides an incentive for habitat protection which could benefit the species. Further research into population trends and ecology are needed to guide management efforts.
Fun Facts
– The Purple-bibbed Whitetip is one of over 325 species of hummingbirds found exclusively in the Western Hemisphere. It is most closely related to its northern relatives such as the Rufous Hummingbird.
– Hummingbirds are the only birds that can fly backwards and upside down. Their wings rotate in a figure eight pattern allowing precision hover-feeding.
– The vibrant plumage colors do not result from pigments but rather the structure of the feathers. The iridescence varies based on viewing angle.
– A hummingbird’s heart rate can reach up to 1260 beats per minute while in flight. Their breathing rate is 250 breaths per minute even while resting.
– To conserve energy, hummingbirds go into torpor at night, lowering their metabolic rate by 50-95%. This is similar to short-term hibernation.
– The Purple-bibbed Whitetip consumes up to half its body weight in nectar each day and feeds on up to 1000 flowers daily. The excess water is eliminated as dilute urine.
– This species undertakes seasonal altitudinal migrations, moving to lower elevations in the non-breeding season. This allows it to follow the bloom of preferred nectar plants.
– The long bill length of each hummingbird species matches the preferred flower shape from which they feed. This bill-flower coadaptation facilitates specialized feeding.
– Costa Rica’s Talamanca Mountains are a biodiversity hotspot with dozens of endemic birds found nowhere else including several threatened hummingbirds.
Conclusion
The newly discovered Purple-bibbed Whitetip Hummingbird highlights the continued surprises found in Neotropical cloud forests. While striking in appearance, it remains critically endangered and in need of habitat protection to ensure its survival. As scientists learn more about this species, it provides insight into unique adaptations and the importance of maintaining connectivity along elevational gradients so species can track their preferred climate zones in the face of global change. Conserving fragile but biodiverse ecosystems will allow elegant birds like the Purple-bibbed Whitetip to continue to dazzle future generations.