Looking very much like swallows, they will soon move north for winter and, despite occasional sightings over the cooler months, most of the population moves at least north of the Great Dividing Range with many going further, to far northern Australia and the New Guinea and Indonesia region.

While most of our local tree martins will depart from the Ballarat district, not all our welcome swallows will go. Admittedly, most will depart, but some will remain at Lake Wendouree and other places where they eke out a wintry existence on the much-reduced population of small flying insects.

Welcome swallows are slightly larger than tree martins, and they have prominent rusty-red foreheads and throats. The tree martin differs in having just a small pale rusty forehead spot, as well as a white rump.

Also sighted alongside the tree martins in the middle of Lake Wendouree last month were two wood sandpipers. These will soon travel internationally - to central northern Asia, where they will nest in coniferous forests. Their nesting habitat is very different from the non-breeding habitat they use in an Australian summer.

Magpie geese seem to now be permanent residents at the lake. Fifteen of them - probably a record - were counted on the islands in the centre at the end of March.

Most of our migratory summer birds have gone and some of the winter birds like the golden whistler, robins and currawongs are moving in. The welcome whistle of the Bassian thrush - expected from damp days in April - has been heard this week in local pine plantations.

Birds departing from the Ballarat district in the past few weeks include the rufous whistler, rainbow bee-eater, sacred kingfisher, satin flycatcher and reed warbler.

The white-winged triller, olive-backed oriole and most cuckoos and songlarks departed earlier in the year.

Migrant dusky woodswallows and black-faced cuckoo-shrikes have not yet left.

A small brown and orange butterfly, often seen resting with front wings raised and rear wings flat, is the green grass dart.

Its unusual stance is distinctive.

This is a native butterfly that has introduced itself to Victoria and the Ballarat district relatively recently.

Green grass - eaten by its caterpillars - attracts it to suburban gardens. The attraction for grass is probably the reason for its name as well, because the butterfly itself is not green at all.

It is a member of the skipper group of small butterflies.