Birds of the Night

Podargus strigoides

A Tawny Frogmouth concealed in a manna gum

On May 19 three Ballarat Field Nats attended a talk hosted by Wombat Forestcare, at Trentham. This was one of a series of talks under the banner of You, Me and Biodiversity. These talks are gaining in popularity so it was nearly standing room only. The next talk is on frogs, check out their website

This talk was presented by Marion Weaving, a PhD candidate from the School of Life and Environmental Sciences at Deakin University, and focused on her research mainly into Tawny Frogmouths. She also discussed the Southern Boobook Owl and the Australian Owlet-Nightjar.

As more and more people live in the urban fringe of cities Marion was interested during her studies to look at 3 nocturnal species that live in the gradient between the forest and suburban fringe, and to determine what landscape and site factors affect their distribution.

Birds are often used in surveys due to their relative abundance and because they are vocal. Many researchers study birds during daylight hours but Marion chose to study birds at the night. She put in an amazing amount of time into this, going out 6 nights a week between dusk and 2am for many months.

Dead Tawny Frogmouth

Close up of a dead tawny frogmouth that had been hit by a car

Initially a lot of work went into determining how to catch the tawny frogmouths, but after about twelve different methods were assessed Marion settled on some small raptor nets from Poland. Small trackers weighing about 19g were attached to the birds via a light harness. The battery gives up after eleven months so the device and harness are removed before this happens. These birds are creatures of habit so they can be easily located as they usually have the same roosting sites.

Call back is the technique used to find if a bird is in the area and this involves playing the call specific to the bird you are looking for by using an MP3 player with speakers. This is a useful especially for owlet-nightjars which are the smallest nocturnal night bird and often goes unseen. It nests in small hollows and in stumps.

Its call is a sound that people are often aware of hearing but rarely realise what makes the it. On one occasion when Marion played the sound of a southern boobook owl the owlet-nightjar almost attacked her in defense of its territory.

Some of the results of the research are that we now know that the tawny frogmouth has a relatively small home range of about 500 metres. They move out of a bush remnant and can be found roosting in interesting places such as satellite dishes and on the edge of swimming pools, in palms, pines, poplars, cotoneasters and Eucalyptus nicholii.

During the breeding season it is the male that sits on the nest during the day. Breeding starts in August. The birds are attracted to lights and compost heaps. They eat moths, small mammals, frogs and are found often near sports grounds where the grass is short and green.

If you ever see a tawny frogmouth staggering around in the middle of the day it is probably about to die. They are susceptible to the toxins in slug and snail baits which is stored and accumulates in their body fat until they succumb and die.

Hollow trees are of high conservation value for a number of species particularly owls like the Southern Boobook, so it is important to retain them whenever possible especially on the urban fringe. Some birds and animals that use hollows for breeding will also use specially designed nest boxes. Australian owlet- nightjars will use boxes but the hole has to be about 7cm and they need to be attached up out of the reach of foxes. Tawnys don’t need hollows as they build a nest made of a few sticks in the fork of a branch about 5-6metres from the ground.

Aegotheles cristatus

Owlet-nightjar peering out of a nestbox

As the tawny feed on or near the ground they are often hit by cars. They have a habit of landing on the ground and forming a hood over their prey with their wings and thus become ready prey for cats and foxes. Ravens and magpies also cause the death the chicks and have been sighted harassing the adult birds so they leave the chicks or get off the nest and leave the eggs.

Tawny Frogmouth

A tawny frogmouth well disguised on some logs

If you have a tawny frogmouth in your area they are hard to find as they blend in with their surroundings but you will probably hear them.


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