Tawny frogmouth

Source: Wikipedia, the free encyclopedia.

Tawny frogmouth

Least Concern  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Clade: Strisores
Order: Podargiformes
Family: Podargidae
Genus: Podargus
Species:
P. strigoides
Binomial name
Podargus strigoides
(Latham, 1801)

The tawny frogmouth (Podargus strigoides) is a species of

nocturnal habits and similar colouring.[2]

Names

In the past, it was sometimes mistakenly called a mopoke or mopawk,[3] a name used for the Australian boobook, the call of which is often confused with that of the tawny frogmouth.

Taxonomy

The tawny frogmouth was first described in 1801 by the English naturalist

Caprimulgiformes.[6] Although related to owls, their closest relatives are the oilbirds, potoos, owlet-nightjars and true nightjars.[5] The earliest fossil evidence of frogmouths is from the Eocene and implies that they diverged from their closest relatives during the early Tertiary.[6] Three subspecies
of the tawny frogmouth are currently recognised:

Description

Rufous morph

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.[6][8][9] 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).[9] In P. s. phalaenoides, a weight range of 205 to 364 g (7.2 to 12.8 oz) was reported.[10] Thus, in terms of average if not maximal body mass, the tawny is a bit smaller than its relative, the Papuan frogmouth.[9] 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.[11] Their eyes are large and yellow, a trait shared by owls.[5] However, they are not forward facing like an owl's.[4]

Tawny frogmouths have three distinct colour

albinistic all-white aberrant plumage for this species has been documented.[12]

Camouflage

Camouflaged tawny frogmouths blend in with colour and texture of tree bark in Sydney.
Camouflaged tawny frogmouth couple in afternoon sun, Melbourne

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.[13] Their silvery-grey plumage, adorned with patterns of white, black, and brown streaks and mottles,[14] enables them to seamlessly blend into the appearance of a fractured tree branch, rendering them nearly invisible in the bright light of day.[15][16]

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.[13] 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.[16]

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.[14] This intricate interplay of behavior and appearance underscores the strategies employed by these birds to ensure their survival within their environment.

Family of four in alarm position, emulating broken branches

Differences from owls

Tawny frogmouths and owls both have mottled patterns, wide eyes and

asymmetrical ears, while tawny frogmouths do not.[4]

Distribution and habitat

Tawny frogmouths are found throughout most of the Australian mainland[16] except in far western Queensland, the central Northern Territory, and most of the Nullarbor Plain.[5] In Tasmania, they are common throughout the northern and eastern parts of the state.[11]

They can be found in almost any habitat type, including forests and

savannahs.[17] However, they are rarely seen in heavy rainforests and treeless deserts.[18] 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.[5] Tawny frogmouths are common in suburbs, having adapted to human presence. They have been reported nesting in parks and gardens with trees.[5]

Behaviour and ecology

Diet and feeding

Tawny frogmouth skull

Tawny frogmouths are

nocturnal insects, such as moths, as well as spiders, worms, slugs and snails,[11] but also includes a variety of bugs, beetles, wasps, ants, centipedes, millipedes and scorpions.[5] Large numbers of invertebrates are consumed to make up sufficient biomass.[5] Small mammals, reptiles, frogs and birds are also eaten.[17]

During daylight hours, healthy tawny frogmouths generally do not actively look for food, though they may sit with their mouths open, snapping them shut when an insect enters.[14] As dusk approaches, they begin actively searching for food. Tawny frogmouths feed mainly by pouncing from a tree or other elevated perch to take large insects or small vertebrates from the ground[6] using their beaks with great precision. Some smaller prey, such as moths, can be caught in flight.[17] Foraging flights consist of short, snatching flights to foliage, branches, or into the air.[5]

Tawny frogmouths do not consume prey collected on the ground or in flight on the spot unless it is very small.

mice are generally killed before consumption by being bashed against a branch with great force.[5]

Bonding and breeding

Tawny frogmouths form partnerships for life, and once established, pairs usually stay in the same territory for a decade or more.

breeding season, pairs roost closely together on the same branch, often with their bodies touching. The male carries out grooming by gently stroking through the plumage of the female with his beak in sessions that can last for 10 minutes or more.[5]

The breeding season of tawny frogmouths is from August to December, but individuals in arid areas are known to breed in response to heavy rains.

leaf litter and grass stems are placed to soften the centre. The nests are very fragile and can disintegrate easily.[5]

The clutch size of the tawny frogmouth is one to three eggs.[6] Both sexes share incubation of the eggs during the night, whilst during the day, males incubate the eggs.[19] For the duration of the incubation period, the nest is rarely left unattended. One partner roosts on a nearby branch and provides food for the brooding partner.[5] Once hatched, both parents cooperate in the supply of food to the young.[16] The fledging period of the tawny frogmouth is 25 to 35 days, during which they develop half their adult mass.[19]

  • Chicks five days after hatching, Melbourne
    Chicks five days after hatching, Melbourne
  • Tawny frogmouth with two 32-day-old chicks, Melbourne
    Tawny frogmouth with two 32-day-old chicks, Melbourne
  • Family of four tawny frogmouths.
    Tawny frogmouth pair with two mature chicks, end of December, Melbourne

Vocalisations

Tawny frogmouths have a wide range of

Nestlings make a number of unique calls expressing distress, hunger and fear. Juveniles retain this range while developing a loud call for begging. Nestlings, juveniles and adults all use a low-amplitude annoyance call meant for family members.[5] When disturbed during rest, they can emit a soft warning buzz that sounds similar to a bee, and when threatened, they can make a loud hissing noise and produce clacking sounds with their beaks.[20]

At night, tawny frogmouths emit a deep and continuous "oom-oom-oom" grunting[20] at a frequency of about eight calls in 5 seconds.[21] The steady grunts are often repeated a number of times throughout the night. They also make a soft, breathy "whoo-whoo-whoo" call at night of lower intensity, but at the same frequency.[5] Before and during breeding season, males and females perform duets consisting of call sequences that either alternate between partners or are performed simultaneously.[5] Tawny frogmouths also make distinctive drumming noises during breeding season.[21]

Thermoregulation

Pair of tawny frogmouths in Brisbane Botanical Gardens

The wide distribution range of the tawny frogmouth includes areas of the Australian continent where winter night temperatures regularly approach or grow colder than 0 °C and warm summers can have extremes above 40 °C.

thermoregulatory
challenge for tawny frogmouths that roost all day out in the open.

Significant differences in the orientation of tawny frogmouths on branches has been observed during winter and summer.

Physiological testing has shown that they are able to triple their breathing rate without the need to open their beaks.[5] However, when their body temperature rises by as much as 4–5°, they begin to pant.[23] Faced with further heat stress, tawny frogmouths engorge the blood vessels in the mouth to increase the flow of blood to the buccal area and produce a mucus that helps to cool air as it is inhaled, and hence cool the body.[24]

During winter, tawny frogmouths choose northerly oriented positions on branches that are more exposed to sunlight to increase body heat.[5] Pair roosting and huddling to share body warmth is also common during winter.[22] During daylight, tawny frogmouths sometimes perch on the ground to sunbathe, remaining motionless up to 5 minutes. During this time, the birds open their beaks wide, close their eyes, and move their heads to the side to allow sunrays to penetrate beneath the thick layer of feathers.[5]

Torpor

During winter, the food supply shrinks drastically and prewinter body fat stores can only provide a limited supply of energy.[25] Tawny frogmouths are unable to survive the winter months without spending much of their days and nights in torpor.[26] Torpor results in energy conservation by significantly slowing down heart rate and metabolism, which lowers body temperature.[25] Torpor is different from hibernation in that it only lasts for relatively short periods of time, usually a few hours. Shallow torpor lasts for several hours and is a regular, daily occurrence in the winter. Dawn torpor bouts are shorter and temperature reduction may be as small as 0.5 to 1.5 °C, while night torpor bouts last several hours and can reduce body temperature by up to 10 °C.[5]

Conservation and threats

Perching on a balcony in Sydney, Australia

The conservation status of tawny frogmouths is "

neurological disease has occurred in tawny frogmouths in the Sydney area, caused by the parasite Angiostrongylus cantonensis, a rat lungworm.[28]

Human impact

Tawny frogmouths face a number of threats from human activities and pets. They are often killed or injured on

land clearing of eucalypt trees and intense bushfires are serious threats to their populations, as they tend not to move to other areas if their homes are destroyed.[29] House cats are the most significant introduced predator of the tawny frogmouth, but dogs and foxes are known to also occasionally kill the birds.[5] When tawny frogmouths pounce to catch prey on the ground, they are slow to return to flight and vulnerable to attack from these predators.[27]

As they have adapted to live in close proximity to human populations, tawny frogmouths are at high risk of exposure to pesticides.[29] Continued widespread use of insecticides and rodent poisons are hazardous as they remain in the system of the target animal and can be fatal to a tawny frogmouth that eats them.[27] The effect of these toxins is often indirect, as they can be absorbed into fatty tissue with the bird experiencing no overt signs of ill health until the winter, when the fat deposits are drawn on and the poison enters the bloodstream.[5]

References

  1. doi:10.2305/IUCN.UK.2016-3.RLTS.T22689580A93237832.en
    . Retrieved 19 November 2021.
  2. ^ a b c d "Myth of the Tawny Frogmouth "Owl"". The Owl Pages. Retrieved 2 June 2014.
  3. ^ Lumholtz, Carl (1889). Among cannibals; an account of four years' travels in Australia and of camp life with the aborigines of Queensland. New York: C. Scribner's sons. p. 33.
  4. ^ a b c d e "Husbandry Guidelines for Tawny Frogmouth" (PDF). NSW Fauna & Marine Parks Association Inc. Retrieved 2 June 2014.
  5. ^
    ISBN 978-0643095090
    .
  6. ^
    ISBN 9780787653620
    .
  7. ^ a b c "Tawny Frogmouth (Podargus strigoides)". Internet Bird Collection. Retrieved 2 June 2014.
  8. ISBN 978-0-19-854987-1
    .
  9. ^
    ISBN 978-1-4200-6444-5
    .
  10. ^ Del Hoyo, J., Elliot, A., & Sargatal, J. (1992). Handbook of the Birds of the World. Barcelona: Lynx Editions.
  11. ^ a b c "Tawny Frogmouth, Podargus Strigoides". Parks & Wildlife Service. Retrieved 2 May 2014.
  12. ^
    S2CID 86375502
    .
  13. ^
    doi:10.1071/mu922307
    .
  14. ^
    ISBN 978-0643103443
    .
  15. ^ "Tawny Frogmouth Fact Sheet, Lincoln Park Zoo"
  16. ^ a b c d e "Tawny Frogmouth – Podargus Strigoides". Australian Reptile Park. Retrieved 2 May 2014.
  17. ^ a b c d "Tawny Frogmouth". Australian Museum. Retrieved 2 May 2014.
  18. ^ a b "Tawny Frogmouth". Perth Zoo. Retrieved 2 May 2014.
  19. ^
    doi:10.1071/mu99024
    .
  20. ^
    ISBN 978-0195532449
    .
  21. ^
    ISBN 978-8487334252
    .
  22. ^
    doi:10.1017/s0952836999008092
    .
  23. doi:10.1071/zo98058
    .
  24. JSTOR 1365559
    .
  25. ^
    S2CID 14302926
    .
  26. ^ a b "Tawny Frogmouths". Backyard Buddies. Retrieved 20 May 2014.
  27. ^ a b c "Tawny Frogmouth". Billabong Sanctuary. Retrieved 20 May 2014.
  28. PMID 23218219
    .
  29. ^ a b "Tawny Frogmouth". SeaWorld Parks & Entertainment. Retrieved 20 May 2014.

Further reading

External links

Wikimedia Commons has media related to Tawny frogmouth.
Wikispecies has information related to Podargus strigoides.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Tawny_frogmouth&oldid=1182669123"