The Hawaiian Islands, situated over 3,200 kilometers from the nearest continent, represent the most isolated archipelago globally. This extreme geographical isolation, combined with diverse climatic conditions, has fostered an extraordinary array of unique life forms. Hawaii is home to over 25,000 unique species, with a significant percentage found nowhere else on Earth. This biodiversity is particularly evident in its avian inhabitants.
Hawaii’s Unique Native Birds
Hawaii’s isolation allowed species to evolve in unique ways, leading to a high degree of endemism among its native birds. Adaptive radiation, where a single ancestral species diversifies into many new forms, each adapted to a specific niche, is a prime example. The Hawaiian honeycreepers, believed to have evolved from an ancestral finch, showcase this phenomenon with over 50 distinct forms.
The Nēnē (Hawaiian Goose, Branta sandvicensis), Hawaii’s state bird, is an endemic species with distinctive adaptations for terrestrial life. Unlike most geese, the Nēnē has longer legs and reduced webbing on its feet, allowing it to navigate volcanic terrain. Though capable of flight, Nēnē are primarily land-dwelling. They exhibit unique social structures, with family units forming dominance hierarchies within flocks.
Another iconic native bird is the ‘I’iwi (Drepanis coccinea), a scarlet-colored Hawaiian honeycreeper with a long, decurved bill. This specialized bill is an adaptation for feeding on nectar from tubular Hawaiian lobelioid flowers, demonstrating coevolution with native plants. ‘I’iwi are known for their varied vocalizations, including whistles, gurgles, and a distinctive “rusty-hinge” call. The ‘Apapane (Himatione sanguinea) is another widespread nectarivorous honeycreeper, characterized by its deep crimson plumage and dark wings. It plays an important role as a pollinator of the native ‘ōhi’a tree.
Birds Introduced to the Islands
Human activity has led to the introduction of numerous non-native bird species to Hawaii, altering the avian landscape. These introductions occurred through various means, including intentional releases for pest control, agriculture, as game birds, or as escaped pets. Unintentional arrivals also occurred, with some species stowing away on ships.
The Common Myna (Acridotheres tristis) was introduced from India. These birds are now common across the islands, recognizable by their dark heads, brown bodies, and yellow eye patches. Another ubiquitous introduced species is the Zebra Dove (Geopelia striata). These smaller doves are frequently seen foraging on the ground in urban and open areas, characterized by their grayish-brown plumage and black and white barring on the neck.
The Red-crested Cardinal (Paroaria coronata), native to South America, was introduced to Hawaii. This species is distinguished by its bright red head, crest, and breast, contrasting with a gray back and white underparts. Various pheasant and francolin species, such as the Erckel’s Francolin and Gray Francolin, were also introduced. These populations have established self-sustaining breeding populations across the islands.
Migratory Birds of Passage
Hawaii’s mid-Pacific location makes it a significant stopover, wintering ground, or breeding site for numerous migratory bird species. These visitors arrive seasonally, connecting the islands to global avian migration patterns.
The Pacific Golden-Plover (Pluvialis fulva), known as Kōlea in Hawaiian, is a well-known migratory visitor. These plovers breed in the Arctic tundra and undertake non-stop flights to wintering grounds, including Hawaii, Australia, and New Zealand. They typically arrive in Hawaii between August and September, often returning to the same territories each year. The Wandering Tattler (Tringa incana) also utilizes Hawaii during its migratory movements.
Seabirds also feature among Hawaii’s migratory visitors. The Laysan Albatross (Phoebastria immutabilis) is a common seabird that breeds primarily in the Northwestern Hawaiian Islands. These birds spend much of their lives at sea, returning to land only to nest and raise their young. Shearwaters also pass through Hawaiian waters during their migratory routes.