Tawny Frogmouth

Identificazione

Tawny frogmouths are large, big-headed birds that can measure from 34 to 53 cm (13 to 21 in) long. Weights have been recorded up to 680 g (1.50 lb) in the wild (and perhaps even more in captivity), but these are exceptionally high. In the nominate race, 55 males were found to weigh a mean of 354 g (12.5 oz), while 39 females weighed a mean of 297 g (10.5 oz), with a range between both of 157 to 555 g (5.5 to 19.6 oz). Among the subspecies P. s. brachypterus, 20 unsexed birds were found to average 278 g (9.8 oz) with a range of 185 to 416 g (6.5 to 14.7 oz). In P. s. phalaenoides, a weight range of 205 to 364 g (7.2 to 12.8 oz) was reported. Thus, in terms of average if not maximal body mass, the tawny is a bit smaller than its relative, the Papuan frogmouth. Tawny frogmouths are stocky and compact with rounded wings and short legs. They have wide, heavy, olive-grey to blackish bills that are hooked at the tip and topped with distinctive tufts of bristles. Their eyes are large and yellow, a trait shared by owls. However, they are not forward facing like an owl's.<p>Tawny frogmouths have three distinct colour morphs, grey being the most common in both sexes. Males of this morph have silver-grey upperparts with black streaks and slightly paler underparts with white barring and brown to rufous mottling. Females of this morph are often darker with more rufous mottling. Females of the subspecies P. s. strigoides have a chestnut morph and females of the subspecies P. s. phalaenoides have a rufous morph. Leucistic or albinistic all-white aberrant plumage for this species has been documented.<p>The tawny frogmouth makes use of cryptic plumage and mimicry to camouflage itself. These birds strategically perch themselves on low tree branches during daylight hours, cleverly assimilating with the tree itself. Their silvery-grey plumage, adorned with patterns of white, black, and brown streaks and mottles, enables them to seamlessly blend into the appearance of a fractured tree branch, rendering them nearly invisible in the bright light of day.<p>In a display of adaptation, the tawny frogmouth typically selects a segment of a tree branch that displays signs of breakage, perching upon it with its head elegantly inclined upwards at a distinctive angle. This posturing, coupled with their large and broad beaks, contributes to the resemblance they achieve. Frequently, a pair of tawny frogmouths will position themselves side by side, simultaneously angling their heads upwards. Only when closely approached do they emerge from their concealed positions, either taking flight or issuing warning signals to potential predators.<p>When faced with threats, adult tawny frogmouths employ a distinctive alarm call that serves as a signal to their chicks. This call instructs the young birds to maintain a state of silence and immobility, ensuring that their natural plumage camouflage remains intact and uncompromised. This intricate interplay of behavior and appearance underscores the strategies employed by these birds to ensure their survival within their environment.<p>Tawny frogmouths and owls both have mottled patterns, wide eyes and anisodactyl feet. However, owls possess strong legs, powerful talons, and toes with a unique flexible joint they use to catch prey. Tawny frogmouths prefer to catch their prey with their beaks and have fairly weak feet. They roost out in the open, relying on camouflage for defence, and build their nests in tree forks, whereas owls roost hidden in thick foliage and build their nests in tree hollows. Tawny frogmouths have wide, forward-facing beaks for catching insects, whereas owls have narrow, downwards-facing beaks used to tear prey apart. The eyes of tawny frogmouths are to the side of the face, while the eyes of owls are fully forward on the face. Furthermore, owls have full or partial face discs and large, asymmetrical ears, while tawny frogmouths do not.

Tassonomia

The tawny frogmouth was first described in 1801 by the English naturalist John Latham. Its specific epithet is derived from Latin strix 'owl' and oides 'form'. Tawny frogmouths belong to the frogmouth genus Podargus, which includes the two other species of frogmouths found within Australia, the marbled frogmouth and the Papuan frogmouth. The frogmouths form a well-defined group within the order Caprimulgiformes. Although related to owls, their closest relatives are the oilbirds, potoos, owlet-nightjars and true nightjars. The earliest fossil evidence of frogmouths is from the Eocene and implies that they diverged from their closest relatives during the early Tertiary. Three subspecies of the tawny frogmouth are currently recognised:

Nome scientifico

Podargus strigoides

Autorità

(Latham, 1801)

Ordine

Podargiformi

Famiglia

Podargidi

Genere

Podargus

Areale e habitat

Tawny frogmouths are found throughout most of the Australian mainland except in far western Queensland, the central Northern Territory, and most of the Nullarbor Plain. In Tasmania, they are common throughout the northern and eastern parts of the state.<p>They can be found in almost any habitat type, including forests and woodlands, scrub and heathland vegetation, and savannahs. However, they are rarely seen in heavy rainforests and treeless deserts. They are seen in large numbers in areas populated with many river gums and casuarinas, and can be found along river courses if these areas are timbered. Tawny frogmouths are common in suburbs, having adapted to human presence. They have been reported nesting in parks and gardens with trees.

Migrazione

Specie stanziale

Comportamento

Comportamento migratorio: Specie stanziale.

Conservazione

Tendenza della popolazione: stabile.

Tendenza della popolazione

stabile