Trogone dalla nuca rossa

Tassonomia

Nome scientifico

Harpactes kasumba

Autorità

(Raffles, 1822)

Ordine

Trogoniformes

Famiglia

Trogonidi

Genere

Harpactes

Areale e habitat

The red-naped trogon is presumed to be a permanent resident or sedentary bird. Sedentary is “commonly used in the special sense of ‘non-migratory,’” and resident is defined as “remaining throughout the year in the area under reference”. At least 4,000 species of bird are regular migrants, which is approximately 40 percentage of the world's population of birds, however the red-napped trogon is not one of these. It does not migrate, but instead remains in the same location all year round.Red-naped trogons are confined to the Sundaic regions lowlands, also known as Sundaland, with a distribution size of 989,000 km2. The Sundaic lowlands is a biogeographical region of South-eastern Asia which encompasses the Sunda shelf, Malay Peninsula of the Asian mainland, and the large islands of Borneo, Java and Sumatra, including their surrounding islands. The eastern boundary of the Sundaic region is the Wallace Line which separates the Indomalaya and Australasia ecotones. <p>The global population size has not been quantified, but the species is described as rare in Thailand, fairly common in Peninsular Malaysia and Sumatra, rather scarce in Sarawak and uncommon in Singapore, Indonesia, Sarawak, Sabah and Brunei. The current population trend shows a decline in the number of red-naped trogons at a moderately rapid rate, owing to habitat loss and degradation throughout its distribution range.

Migrazione

Resident species

Comportamento

Red-naped trogons are generally inactive outside of their regular feeding patterns. Because of this, birdwatchers and biologists have noted that “apart from their general beauty, they are notorious for their lack of other immediately engaging qualities”. Their lack of activity has been considered a defence against predation. As with other Trogonidae species, red-naped trogons have been reported to shift along branches to keep their dull coloured backs turned towards observers, while their heads, which can rotate at 180 degrees like owls, are turned to keep watch on any potential predators. They are preyed upon by hawks and predatory mammals.<p>The red-naped trogon is mainly insectivorous, feasting on arthropods with a preference for stick insects and spiders. This regime is embellished with small lizards, fruits and seeds. The word “Trogon” is Greek for “to gnaw or eat” and refers to the structure and function of their beaks. The cutting edges of the maxilla and mandible are serrated which aids in securing live prey and fruit. These serrations, along with the decurved tip of the bill, are also useful in cutting food items into smaller pieces. Prey is mostly obtained on the wing, with the most commonly used foraging technique known as sally-glean flight. This is where the red-naped trogon flies from an observation perch to a target on another perch or in the foliage. Once in position, the red-naped trogon hovers over its target before snatching up they prey and returning to its original perch to consume the prey.<p>The red-naped trogon's song voice is a slow, sad-sounding five to eight note “pau pau pau pau pau.” Each short note slightly down slurred (1.5-1.2 kHz) and delivered at a rate of c.1 note/s. In addition to the territorial and breeding calls given by males and females during the breeding seasons, red-naped trogons have also been recorded as having aggression and alarm calls.<p>The red-naped trogon is a territorial and monogamous species. The males repel other members of the same species, and even other nesting species, from around their nesting sites to ensure the safety of the nest. The males attract females by singing. Flocks of 3-12 individuals have been observed prior to, and sometimes during the breeding season, calling and chasing each other, however, the function of these flocks is unknown. Little is known about the nesting habits of the red-naped trogon, only that they are assumed to be cavity nesters. The only recorded account of a red-naped trogon nest was that of a brood found in July 1976 in Peninsular Malaysia. The nest was dug in a cavity of a rotten stump a few meters off the ground. They produce a clutch size of between one and three eggs. The incubation period lasts between 16 and 19 days. Upon hatching, the chicks are altricial, blind and naked, however, they do acquire feathers rapidly. The nesting period generally takes between 16 and 23 days to fledge. The red-naped trogon occurs mainly in primary, or lightly logged, lowland evergreen forests. They are most abundant below 600 metres, but have been located occasionally up to 1,200 metres in montane dipterocarp forest in Borneo. Another location that they have been recorded in is peat-swamp forest, as well as some logged areas, thick bamboo groves, coconut and cocoa plantations.

Conservazione

Tendenza della popolazione

declining