Species Information: Manu-o-Kū or White Tern
The Manu-o-Kū, also known as the white tern, is a small and striking seabird belonging to the Laridae family. It can be found across various tropical regions around the globe, making it a truly pantropical species. This tern stands out with its pristine white feathers, dark eyes, and a distinctive black bill that tapers to a sharply pointed end, accentuated by an electric blue base.
One of the noteworthy features of the Manu-o-Kū is that adult males and females bear an identical appearance, with no notable variations in plumage throughout the year. This lack of sexual dimorphism sets them apart from many other bird species, adding to their allure.
In flight, the Manu-o-Kū displays a buoyant and free-spirited behavior, often accompanied by erratic changes in both speed and direction. This graceful aerial display adds to their charm, captivating observers fortunate enough to witness their flight.
As for their feeding habits, the Manu-o-Kū employs two primary techniques: surface dipping and surface diving. These birds have a propensity for joining hunting parties formed by several other species, leveraging the advantage of collective hunting. Being piscivorous, they primarily target fish that are driven towards the water's surface by larger predatory species.
In the beloved islands of Hawai‘i, the Manu-o-Kū's diet predominantly consists of juvenile goatfish and flying fish—a testament to the rich marine diversity found in the waters surrounding the archipelago. The ability of the white terns to adapt their feeding preferences to the local offerings underscores their adaptability and resourcefulness as a species.
With its elegant appearance, mesmerizing flight patterns, and skillful foraging abilities, the Manu-o-Kū or white tern stands as both a visual delight and a testament to the wonders of the natural world. Its presence in tropical regions serves as a reminder of the interconnectedness and delicate balance of ecosystems that foster such unique and beautiful creatures. The Manu-o-Kū, also known as the white tern, is a fascinating bird that exhibits unique behaviors compared to most other terns. These breeding adults prefer to remain close to their nest sites and commonly forage in inshore areas such as shoals and banks, occasionally venturing into offshore waters. Unlike many tern species that gather in large colonies, the Manu-o-Kū opts for nesting in loosely associated groups or even on their own.
What sets the Manu-o-Kū apart from other terns is their strong pair bonding. These beautiful birds often stay paired for several seasons and display remarkable fidelity to their nest sites, frequently returning to the same spot year after year. Interestingly, the Manu-o-Kū does not construct nests like many birds do. Instead, the female lays a single egg wherever she finds a suitable depression. These nests can be found on various surfaces, including tree branches, buildings, man-made structures, rock ledges, or even on the ground.
In the Hawaiian archipelago, the Manu-o-Kū breeds throughout the year, although the majority of eggs are laid between the months of February and June. If an initial nest fails, pairs will replace the egg and continue their breeding efforts. In fact, it is not uncommon for some pairs to successfully raise two or even three sets of offspring in a single year.
Both parents play an active role in the incubation of the egg, as well as in brooding and feeding the chicks. This shared responsibility highlights the strong partnership between the male and female. After hatching, the newly-flying young birds remain dependent on their parents for up to two months, relying on them for guidance and sustenance as they learn to navigate the world around them.
Interestingly, the Manu-o-Kū reaches sexual maturity at the age of five years. It is during this time that they embark on their own breeding journey, marking the beginning of a new generation. The oldest known individual of this species lived an impressive 42 years, emphasizing their remarkable longevity.
The Manu-o-Kū, with its unique nesting habits, strong pair bonding, and year-round breeding, is a remarkable bird. Their ability to adapt to various nesting surfaces and their dedication to raising offspring sets them apart from other tern species. As these graceful birds continue to thrive in the Hawaiian islands, they serve as a symbol of the innate beauty and resilience of nature.

Distribution:
The Manu-o-Kū, also known as the white tern, is a seabird that demonstrates a varied distribution across different geographic regions. These graceful birds breed in the Northwestern Hawaiian Islands (NWHI) as well as on the island of O‘ahu in Hawaii. However, their breeding range extends beyond the Hawaiian Islands. White terns can be found breeding on islands throughout subtropical and tropical oceans around the world, although their breeding in the southern Atlantic Ocean is limited.
Outside of their breeding range, the non-breeding distribution of the white tern remains unknown. While it is unclear where they specifically migrate to during the non-breeding season, it is believed that these birds typically stay close to their breeding colonies year-round and seldom venture far from shore. This behavior indicates that white terns may not undertake long-distance migrations like some other bird species.
Habitat:
The Manu-o-Kū primarily breeds on oceanic islands, encompassing a range of habitats. They can be found nesting on both low-lying coralline sand islands and high volcanic islands. Rather than building nests, white terns lay their eggs in suitable depressions or surfaces they can find. This includes a variety of nesting sites such as volcanic pinnacles, cliffs, rocky slopes, large bushes or trees, and even man-made structures.
In marine habitats, the white terns are closely associated with nearshore waters. They rely on the ocean for sustenance and engage in behaviors such as diving to catch fish or other small marine creatures to feed themselves and their young. The proximity to the coast allows them easy access to their food sources and ensures their survival despite their preference for staying near their breeding colonies.
Overall, the distribution of the Manu-o-Kū is not only limited to the Hawaiian Islands but extends throughout subtropical and tropical oceans, emphasizing their adaptability to different habitats and their ability to thrive in a diverse range of environments.

Threats to Manu-o-Kū (White Tern) Population in Hawaiian Islands
The beautiful and delicate manu-o-Kū, also known as the white tern, faces several threats to its population in the Hawaiian Islands. These threats range from the invasion of introduced predators to the consequences of overfishing.
One of the primary threats that the manu-o-Kū faces is from introduced predators, namely rats and feral cats. Seabirds, including the manu-o-Kū, are vulnerable to predation by these invasive species, which can have devastating effects on their adult birds and nests. Fortunately, all sites in the Northwestern Hawaiian Islands (NWHI) have successfully eliminated rats and cats, creating a safe breeding environment for the manu-o-Kū. However, historically, Midway Island experienced predation from rats, which likely preyed on their eggs, young, and adult birds.
Another threat facing the manu-o-Kū is the introduction of insects to their nesting habitats. On Midway Island, big-headed ants have been observed attacking pipped eggs and incubating adults, posing a significant risk to the survival of the manu-o-Kū population. Additionally, on Kure Island, scale insects, which are foreign to the ecosystem, are killing native vegetation. While the exact impact of these insects on the manu-o-Kū remains unknown, it is crucial to monitor their effects to ensure the long-term health of the white terns' habitat.
The third threat that has the potential to affect the Hawaiian populations of the manu-o-Kū is overfishing. Being dependent on predatory fish to drive prey to the surface, the white tern relies on a healthy and balanced marine ecosystem. If overfishing continues unabated, it may disrupt the population of predatory fish, ultimately disrupting the natural food chain and threatening the manu-o-Kū's ability to find sufficient food resources.
In conclusion, the manu-o-Kū population in the Hawaiian Islands faces several threats that could significantly impact their survival. While the removal of rats and cats from nesting sites in NWHI is commendable, it is vital to remain vigilant in monitoring and preventing the introduction of predatory insects. Additionally, sustainable fishing practices and efforts to maintain a balanced marine ecosystem are crucial to ensure the continued success of the manu-o-Kū population in Hawaii. Protecting these beautiful seabirds is not only a conservation imperative but also an acknowledgment of their ecological significance in maintaining the delicate balance of the Hawaiian ecosystem.