Wednesday, 30 September 2015

Frogmouths incubating

A pair of Tawny Frogmouths Podargus strigoides at their nest site - can you spot them
September is the month when most tawny frogmouths in the Canberra area lay their eggs and begin their four-week incubation. This year, the earliest birds laid on the 26th August and the last ones have yet to lay, which is typical of the spread that I have found in the past several years. I monitor about fifty pairs in my studies of these birds, and they are rather difficult to find as they are well concealed. Yet every time I do find a pair at their nest site I cannot help but admire their adaptation to their habitat.

The male sitting on the nest set in the fork of a tree - tricky to see in the typical dappled light
The male incubates the eggs during the day while the female sits quietly in a nearby tree. Neither will move when approached apart from shifting their posture, usually to an erect stretched pose by which they blend into the shape of a branch. As their colouring also resembles that of a dead branch, they simply disappear into the wood.

The female sits on a dead branch high in an adjacent tree
The dead branch posture is the one most people are familiar with if they come across a bird, but most of the time they sit fluffed up and bask in the sunshine. Some of the birds I study are familiar with me as I have visited them several times a year over the years, they probably recognize me. And it is probably because the birds have seen me so often that they do not go into their branch pose. I have been right next to birds as they have cocked their head right back and opened their feathers to catch the sun. I always prefer to study undisturbed birds so it is especially pleasing to be accepted as not a threat by a wild animal.

A female basking in sunshine, with loose feathers and head tilted to catch the sun

A female adopts the stick-pose, where she resembles a dead branch in colour and shape
As a little footnote, not all the birds build their nests in a branch fork, some use old nests of other birds. And a favourite old nest is that of the white-winged chough. These are mud nests, set half-way along a lateral branch and the frogmouths add just a few sprigs of leaves and twigs to the cup of the mud nest. This might give the birds a more secure nest site than the usual flimsy loose platform balanced in a fork, but they are more obvious to predators. Over the years, I'll gather information on whether the birds that use old chough nests are more or less successful at rearing young than those that use conventional nests.

A Tawny Frogmouth sitting on his nest in an old White-winged chough Corcorax melanorhamphos nest

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