Hawaii Amakihi

The Hawaii ‘Amakihi (Chlorodrepanis virens), commonly referred to as the common ‘Amakihi, is one of the most widespread and adaptable of the Hawaiian honeycreepers. This small, vibrant bird has successfully thrived in a variety of habitats across the Hawaiian Islands, showcasing remarkable resilience in the face of environmental changes and emerging diseases.

The Hawaii ‘Amakihi is a small bird, measuring approximately 10 centimeters (3.9 inches) in length. It is predominantly yellow-green, with a slightly curved black bill measuring about 1.3 centimeters (0.51 inches). The bird’s eyes are brown with black pupils, adding to its sharp and alert appearance. Males are typically brighter in color than females, with the vibrant yellow-green plumage serving as a key distinguishing feature.

Physical Characteristics at a Glance

Taxonomy

The Hawaii ‘Amakihi was originally classified in the genus Hemignathus but was reassigned to the genus Chlorodrepanis following a phylogenetic analysis of mitochondrial and nuclear DNA sequences. This reclassification reflects a more accurate understanding of the bird’s evolutionary relationships within the honeycreeper family, Drepanididae.

Subspecies

There are two recognized subspecies of the Hawai’i ‘Amakihi:

1. C. v. wilsoni: Found on the islands of Maui, Moloka’i, and historically on Lāna’i.
2. C. v. virens: Native to the Big Island of Hawai’i.

These subspecies exhibit slight variations in size and coloration, with C. v. wilsoni generally found at higher elevations compared to C. v. virens.

Distribution and Range

The Hawai’i ‘Amakihi is one of the most widely distributed honeycreepers, found on the Big Island, Maui, and Moloka’i. It was last seen on Lāna’i in 1976, where it is now considered extirpated. The bird inhabits a wide range of environments, from dry māmane forests to mesic and wet forests, at elevations ranging from sea level to 2,400 meters (8,000 feet). Remarkably, on Maui, the Hawai’i ‘Amakihi has also adapted to forests dominated by introduced species like pines, cypresses, and firs.

Population Estimates and Distribution

The population of Hawai’i ‘Amakihi is stable and robust across its range. Below is a table summarizing the estimated population sizes on different islands:

The Hawai’i ‘Amakihi is currently listed as “Least Concern” by the International Union for Conservation of Nature (IUCN), largely due to its stable population and adaptability.

Habitat

The Hawai’i ‘Amakihi is highly adaptable, occupying a variety of habitats across the Hawaiian Islands. These include:

• Dry Māmane Forests: Found primarily at higher elevations on the Big Island, these forests are characterized by the presence of the māmane tree (Sophora chrysophylla), an important food source for the ‘Amakihi.
• Mesic Forests: These forests receive moderate rainfall and provide a mix of native and introduced plant species.
• Wet Forests: These areas are typically found at higher elevations and are dominated by native species like ‘ōhi’a lehua (Metrosideros polymorpha).
• Introduced Forests: On Maui, the ‘Amakihi has successfully colonized forests composed of non-native species, demonstrating its adaptability.

Behavior

The Hawai’i ‘Amakihi is known for its energetic and curious nature. It is often observed flitting through the forest canopy, foraging for food, and defending its territory. Unlike some other Hawaiian honeycreepers, the ‘Amakihi is less affected by habitat disturbance, allowing it to thrive in altered environments.

Vocalization

The primary song of the Hawai’i ‘Amakihi is a rapid trill, which varies slightly between individuals. This trill is used both for communication between mates and to establish territory. In addition to their song, ‘Amakihi produce a variety of calls, including soft chirps and whistles.

Feeding

The Hawai’i ‘Amakihi has a diverse diet, which has enabled it to adapt to a wide range of habitats. Its primary food sources include nectar, fruits, insects, and spiders.

Diet Composition

The ‘Amakihi has a specialized tubular tongue that allows it to extract nectar from flowers such as those of the ‘ōhi’a lehua and māmane. When nectar is scarce, the bird will turn to fruit and even juice from overripe fruits. Insects and spiders are a crucial part of the diet, especially during the breeding season, providing the necessary protein for raising chicks.

Breeding

The Hawai’i ‘Amakihi has a long breeding season, lasting up to nine months. This extended period allows for the possibility of raising two broods within a single season, a strategy that contributes to the species’ population stability.

Breeding Characteristics

• Nesting: The ‘Amakihi typically builds its nest high in the canopy, using twigs, leaves, and moss. The nest is well-hidden, providing protection from predators.
• Clutch Size: The female usually lays 2 to 3 eggs, which are incubated for about 14 days.
• Fledging: Chicks remain in the nest for 15 to 21 days before fledging. After fledging, they are fed by the parents for an additional 2 to 3 months until they become fully independent.

Threats

Despite its adaptability, the Hawai’i ‘Amakihi faces several threats:

• Habitat Loss: Urbanization and agricultural expansion have led to the loss of native forests, particularly at lower elevations.
• Invasive Species: Predators such as rats and mongooses pose a significant threat to nests and young chicks. Additionally, invasive plant species can alter the composition of the forests, reducing the availability of native food sources.
• Disease: Avian malaria and avian pox are significant threats to Hawaiian honeycreepers. However, the Hawai’i ‘Amakihi shows signs of developing resistance to these diseases, which has contributed to its survival in lower elevation areas where these diseases are more prevalent.

Migration and Movements

The Hawai’i ‘Amakihi is generally a resident bird, with no long-distance migration observed. However, seasonal movements are common, particularly in response to the availability of food resources. During periods of nectar abundance, ‘Amakihi may move to higher elevations or wetter forests. Conversely, when food is scarce, they may descend to lower elevations or explore new habitats, including non-native forests.

Conservation Status

The Hawai’i ‘Amakihi is currently listed as “Least Concern” by the IUCN due to its stable population and adaptability to different habitats. Nevertheless, ongoing conservation efforts are crucial to ensuring the long-term survival of this species, particularly in the face of habitat loss and disease.

Conservation Strategies

Conservation efforts for the Hawai’i ‘Amakihi include:

• Habitat Protection: Preserving native forests and restoring degraded habitats are essential for maintaining healthy ‘Amakihi populations.
• Invasive Species Control: Managing populations of invasive predators and plants is crucial for protecting nests and ensuring the availability of native food sources.
• Disease Management: Research into disease resistance and vaccination programs for avian malaria and pox is ongoing, with the aim of protecting not just the ‘Amakihi but other vulnerable honeycreeper species as well.

Conclusion

The Hawai’i ‘Amakihi is a testament to the resilience and adaptability of Hawaiian honeycreepers. Its ability to thrive in a variety of habitats, coupled with its potential resistance to diseases that have devastated other native birds, makes it a unique and important species in Hawaii’s ecosystems. Conservation efforts aimed at protecting and restoring its habitat, controlling invasive species, and managing disease threats will be key to ensuring that the Hawai’i ‘Amakihi continues to thrive for generations to come.