Aldabra fody

The Aldabra fody was described as Foudia aldabrana by Robert Ridgway in 1893, based on several specimens, both male and female, at the American Museum of Natural History. The specimens had been collected by William Louis Abbott from Aldabra Island the previous year. Ridgway commented on their similarity to Foudia madagascariensis, while noting that F. aldabrana was much larger. The species has since been synonymized with F. eminentissima, the Cormoros fody, by some researchers, and was once treated as such by the International Union for the Conservation of Nature (IUCN). However, following the reaffirmation of F. aldabrana as distinct from F. eminentissima by multiple authors in the 2010s, the IUCN began assessing the Aldabra fody as a separate species on its Red List of Threatened Species. F. aldabrana is nested within a clade that includes F. madagascariensis and F. omissa. The species is monotypic. The Aldabra fody has been known to hybridize with its relative the Madagascar fody, an invasive species on Aldabra. The Madagascar fody is thought to have reached Aldabra by way of Assumption Island, where they were introduced in 1977 for aesthetic purposes. An eradication program reduced the population on Assumption over 99% by 2015, and similar efforts have begun on Aldabra. A 2015 study found no indication of hybridization between the two species prior to human contact, stating that the birds most likely colonized the island before the start of the eradication program on Assumption. Hybridization between the species has occurred in a region known as Takamaka in the eastern part of the atoll, and the results of the study suggested that the invasive birds had not yet reached other areas. The majority of crosses appeared to have been between male Aldabra fodies and female Madagascar fodies, producing offspring intermediate between their parents in size. ==Description==

The Aldabra fody's bill is markedly long and heavy, a distinctive characteristic. Immature birds are similar to the female. All plumages contain yellow tones, and all are more yellow than the related Comoros and Madagascar fodies, especially on the underparts. Voice There were no published recordings of the Aldabra fody's vocalizations as of 2013, but they have been well-described. There are a great variety, with many based on high-pitched and metallic two-eet, twee, or tee calls. They produce a trilling song sequence consisting of a variety of notes, described by one study as tsee-oo tsee-oo tsee-oo fsssssss looklooklooklooklook. Males generate a nasal "fizzing" noise associated with territorial defense, suggested by one ornithological encyclopedia to correspond to the fsssssss noise reported in the study. Birds advertise their territory with clear and loud tweet tweet two-eet, or simply tweet or two-eet notes. They may also produce three rapid, lower notes followed by two or three higher notes with more deliberation: teetiti twee twee. Males and females have different alarm sounds, with males trilling excitedly while females scold loudly and continuously (tic-tic tzip tic tzip tzip tic-tic). Females give a zeep zeep when soliciting copulation, with a psep pseep after mating. ==Distribution and habitat==

to Aldabra (coast pictured), an atoll in Seychelles. The Aldabra fody is endemic to Aldabra, an atoll located about northwest of Madagascar, belonging to Seychelles. The species is widespread on Aldabra, found on all main islands, as well as smaller islets of the lagoon. The atoll, which makes up one third of the total land of Seychelles, is protected by the government as a nature reserve. "Cardinals" reported on Astove and possibly Cosmoledo in the 19th century may have been the Aldabra fody, but there is no proof of this. The Aldabra fody can be found in scrub, Cocos nucifera groves, or Casuarina woodland. Their territories may be as little as in groves of large trees, which could indicate a possible forest ancestry, although there are no forests on Aldabra. ==Behavior and ecology==

Reproduction Adult males spend most of the year defending and maintaining nesting territories. They are strongly territorial, with a characteristic threat display consisting of drooping the wings and tail while puffing out the feathers of the head, breast, and rump. The eggs, which are laid in clutches variously reported as containing 2–4 eggs, are pale glaucous green (approaching blue), unspotted, and elongate ovate in shape, with thin, glossy shells. Due to the strength of their bills, this may be due to unfamiliarity. The large bill may be a product of adaptive radiation, designed to compete with other land-dwelling birds of the atoll by exploiting all available sources of food. ==Conservation==

The Aldabra fody's nesting success may be very low due to the rate at which nestlings and eggs are taken by predators such as the pied crow and black rat. Increasing drought conditions on the atoll are impacting the birds' habitat. Hybridization with the Madagascar fody has been cited as a threat to the Aldabra fody's genetic integrity, although the IUCN has stated that successful effort to eradicate hybrid fodies means that hybridization is not currently causing a decline in the overall Aldabra fody population. The organization has designated the species as endangered. ==References==