Branching out (above): the tawny frogmouth’s ‘eyebrows’ seem to add to its resemblance to a dead snag © Shutterstock.com/Wright Out There
Supreme in the art of camouflage, the tawny frogmouth is a favourite bird-park subject with a character to match its zany appearance. BILL NAYLOR reports on a true avian oddity
WHILE there are many birds that wait for food to come their way, the large nightjar relatives known as frogmouths (family: Podargidae) are among the only bird species whose camouflage enables them to be in full view yet remain virtually undetected. Not only do they resemble the colour of the branch or stump on which they are perched, but they can transform their appearance by contorting their body shape, reducing their eyes to slits and tightening their feathers. The result is that they resemble a broken tree limb covered with grey mottled bark.
Although frogmouths are nocturnal, they are also active during dusk and dawn and semi-active during the day, sometimes sunbathing, wings extended, on open ground or roadsides, which makes them vulnerable. At Australia’s Taronga Zoo, wild frogmouths would sunbathe near the frogmouth aviary, prompting excited zoo visitors to inform me and other birdkeepers: “The frogmouths have escaped!” A tawny frogmouth’s camouflage matches the dead trees that abound in the Outback, but they are also found in suburban areas such as parks and gardens. After dark their deep bass-level, slightly irritating, monotonous om-om-om-om call can often be heard.
They sometimes perch near paths in plain sight for hours, as humans walk past oblivious. If anybody inspects this suspicious “tree stump”, the frogmouth doesn’t immediately fly away. Instead, it launches into an impressive threat display. The sudden appearance of the large yellow owl-like eyes is startling enough. Then it displays its wide bright yellow gape and pink throat, before clicking its beak loudly as it raises the feathers around its face and fluffing out its contour feathers to appear bigger.
This is usually enough to stop any animal or human in its tracks, as the frogmouth escapes calmly on silent wings. Its strange looks and marvellous camouflage ability have made it a popular exhibit in zoos and bird parks.
Frogmouths and their relatives
The 16 species of frogmouths, occupying three genera, occur in Asia and Australasia. They are closely related to the nightjars and potoos and, more distantly, to swifts. The tawny frogmouth (Podargus strigoides) is the commonest of three frogmouth species that occurs in the Australasian region and at 40cm (16in) long it is one of the larger species. Frogmouths were originally thought to feed like nightjars and swifts, catching their food in their large shovel-shaped gapes while flying. Although it has a wingspan of 90cm (30in), its wings are broad, its tail is short and it lacks manoeuvrability in the air. Insects are either caught in mid-air, a short distance from their perch, or on the ground. Like all its close relatives the tawny frogmouth’s feet are small and ineffective for restraining larger prey. When seized, prey that tries to escape is grabbed securely and usually killed with the large hooked beak. But it often does this clumsily and stomach content analysis has revealed that soil and other ground debris is often swallowed too.
Adults are sometimes reluctant to pick up dead food and are usually hand-fed a combination of mice, strips of meat and day-old chicks. However, if food is placed in a dish fixed to a perch, they will learn to feed themselves. Roughage is essential as frogmouths regurgitate pellets following a meal. They strongly dislike food that sticks to their beak.
The plumage varies depending on where they are, and from individual to individual. If housed indoors, the plumage turns brown, but when returned to an outside aviary they assume their normal grey. Pairs may have different coloured plumage, but it’s not a reliable indicator of sex. However, the male is said to have an orange-brown ring round the iris, which is absent in the female. The frogmouths in the genus Batrachostomus have small oil glands, but the tawny, like other Podargus frogmouths, lacks an oil gland. This species does have powder-down areas of plumage on either side of the rump. These small feathers break up into a fine powder and are used when preening to coat the plumage dark grey.
Pairs of frogmouths are affectionate, like owl partners. Ideally, pairs should be housed alone, since during the breeding season a group will fight and peck each other till one can grab another’s mouth and hold on with their hooked bill. This is not always observed as it occurs at dusk or during the night, when they are most active and aggressive.
It is often stated that frogmouths don’t drink, but in hot weather they can be observed do so, and often drink when bathing in a pond, which they enjoy. An aviary should offer shade and vertical stumps. Some zoos install dimmed nightlights, which attract insect prey.
The first recorded breeding of this species was in 1956 and it has been bred a number of times since. The nest of sticks is a flimsy see-through affair high in the fork of a tree. In captivity, they will make use of a tray or mesh basket. Placing a thin layer of twigs and straw will hasten breeding, as frogmouths are slowcoaches when it comes to nest-building. Where there is deep litter on the aviary floor, they will sometimes nest with no additional nesting material. The female often sits on the nest for a week or so before laying two white round eggs. These appear three days apart and are incubated by both parents for 28-30 days.
Young tawnies have white down and are very noisy when the parents arrive with food. Initially this is insects, but other food is introduced as they grow. Their droppings are particularly watery and foul smelling, which is normal and not a sign of disease. When they fledge at 36-42 days, they often clamber around the nesting tree. They do not feed independently until they are about 80 days old. Fledgling tawny frogmouths, which are the same size as the adults, are often handed into zoos and wildlife hospitals, probably because they leave the nest before they can fly and are assumed to be orphaned. They are easy to hand-rear and become very tame but are still clumsy when hand-feeding and can accidentally grab your fingers, which is when you appreciate the force of their beak which is as strong as an owl’s.
A group of fledgling frogmouths can be housed in an aviary without them fighting. When young, frogmouths often have a whitish film over the eyes, which clears as they get older.
Bill Naylor worked at zoos and bird parks all over the world, during a career spanning more than 40 years.
A replaceable tongue
Frogs, scorpions and similar-sized prey items are bashed on a branch to kill them, and in doing so not infrequently the potoo injures its white paper thin tongues. When this happens the end of the tongue will usually dry and drop off, and a new replacement part of the tongue will eventually grow.
Happy at Paulton’s
With few predators other than birds of prey, tawny frogmouths have survived for as long as 14 years in the wild and can live twice as long in captivity. In 2013 at Paulton’s Park, Hampshire, a male frogmouth aged 33 and a female aged 29 successfully reared a youngster. The male had previously reared eight youngsters.
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