Hawaiian gallinule

The Hawaiian gallinule (Gallinula galeata sandvicensis) is an endangered subspecies of the common gallinule that is endemic to the tropical Hawaiian Islands. It is also variously known as the Hawaiian common gallinule, Hawaiian moorhen, Hawaiian common moorhen, mudhen, or ʻalae ʻula ('burnt forehead' - for its prominent red frontal shield) in Hawaiian, and sometimes misleadingly as the Hawaiian red coot. It is a

It is dependent on freshwater wetland habitats with dense emergent vegetation for nesting. Once found on most of the main islands of the Hawaiian archipelago, it has undergone a major population and range decline and is now a resident breeder only on Kauaʻi and Oʻahu. Causes of the decline were mainly loss of habitat, hunting and predation by introduced animals, with numbers subsequently stabilised at a low level through legal protection and conservation management. Despite being hunted for food, it was mythologised as the keeper of fire in Hawaiian religion.

It is likely that the Hawaiian gallinule is descended from stray migrant common gallinules from North America. It was formerly treated as a subspecies of the common moorhen, and subsequently as a subspecies of the common gallinule when that species was split from the common moorhen in 2011. It is distinguished from other subspecies by a larger frontal shield and a red blush on the front and sides of the tibiotarsus.

The Hawaiian gallinule has dark grey-brown upperparts, black head and neck, dark slate-blue underparts, with mostly white undertail coverts and white flank stripes. It has a large red frontal shield over a red, yellow-tipped, bill. The long, sturdy legs and long-toed feet are mainly yellowish-green. Sexes are similar. The body length of the gallinule is about 33 cm. The average body mass of adult birds is 350 g. Immature birds are olive- to greyish-brown, with duller pale yellow to brown bills.

The gallinule is easily distinguished from the only similar bird in its range, the Hawaiian coot, by the latter's white frontal shield. Its vocalisations have been described as “chicken-like cackling calls and croaks which are louder and higher pitched than the coot's”.

The gallinules are secretive birds, spending much time in dense wetland vegetation. While feeding in the open they will quickly seek cover when disturbed. At some locations, however, individuals are quite tame and will even approach humans. Despite the lack of webbing or lobes on their toes, the birds are good swimmers. They moult over a period of about 25 days each year, normally between June and September, when they are unable to fly and so more vulnerable to predation.

Breeding may occur throughout the year, peaking from March to August; it is affected by water levels and vegetation growth. Nesting pairs are territorial, with territory size measured at 850–2400 m². Nests are generally sited inconspicuously within dense vegetation above shallow, standing, fresh water not more than 60 cm deep. The nests are constructed on platforms of flattened or folded vegetation close to the water surface, with flooding being a major cause of nesting failure. Nests are about 26 cm across, with an inside diameter of 16 cm and a depth of 5 cm. Average egg size is 44.1 mm x 31.5 mm. Clutch size is usually five or six, with an incubation period of 19–22 days. When the chicks hatch, the adults eat or remove the eggshells from the vicinity of the nest site. The chicks are precocial, and are able to walk and swim soon after hatching, but depend on their parents for protection and feeding for some 21–25 days, after which they begin to feed independently.

The birds forage in and near dense wetland vegetation. They are opportunistic feeders, consuming a variety of plant material (such as algae, grass and seeds) and invertebrates (including molluscs and aquatic insects).