The Magpie-lark (Grallina cyanoleuca) is a conspicuous Australian bird of small to medium size, also known as the Mudlark in Victoria and Western Australia, the Murray Magpie in South Australia, and as the Peewee in New South Wales and Queensland. It is currently thought to be related to fantails in the family Dicruridae.
It is a common and very widespread bird both in urban and rural areas, occupying the entire continent except for Tasmania and some of the inland desert in the far north-west of Western Australia, and appears to have adapted well to the presence of humans.
Birds generally pair for life (though divorce is not unknown) and defend a territory together. The nest is round, about 150 mm in diameter, usually placed on a flat branch somewhere near water, made of grass and plant material thickly plastered together with mud, and generously lined with grass, feathers and fur. Breeding is opportunistic, usually from August to February in the fertile south, anytime after rain in drier areas, and multiple broods are common when conditions allow. Both parents incubate a clutch of between three and five eggs.
Group gatherings of magpie larks have been observed with loose "flocks" comprising dozens of individulas being observed perched on vantage points. Such behavious is common paricularly in productive agricultural areas. This behaviour may be pairing or breeding related or simply indicate a boutiful feeding area. The Magpie-lark is aggressively territorial, and will fearlessly defend its territory against larger species such as the Australian Magpie, Crow, Laughing Kookaburra, and even the Wedge-tailed Eagle. They are not known to attack people.
Traditionally, it has been thought that the function of duet singing (not just in Magpie-larks but birds more generally and indeed in mammals, insects and frogs) was to defend a territory or to maintain the pair-bond. More recently it has been proposed that it serves to guard against infidelity—that the male sings to attract a mate, and the female joins in to let her rivals know that this particular male is already taken. Duet singing remains fairly poorly understood as a great deal of the existing research on birdsong has been carried out in the Northern Hemisphere, where a fairly small number of female birds sing.
In the case of the Magpie-lark, the duet singing is now known to be cooperative: pairs sing together to defend their territory. Magpie-larks sing more vigorously in response to duet calls from other birds than they do to the call of a single rival, and more vigorously still if the callers are strangers rather than established and familiar birds from a neighboring territory. A pair of neighbors calling from the 'wrong' place, however, (as when calls are recorded and played back by an experimenter) bring forth a powerful reaction: clearly, they know exactly who their neighbors are.