Most seaweeds are actually algae. Today's photo shows a local type. This is a species found on damp ground or in shallow water. Its spherical shape and its outside skin make it very different from the spreading, rather formless shapes of some of the other larger algae species.

With the scientific name of Nostoc, this one is sometimes known as Nostoc algae balls. The photo has enlarged the spheres, most of which are a little smaller than rabbit droppings. They are often found in aggregations or colonies. This colony was near Lake Wendouree, on damp open ground, covering perhaps half a square metre.

The soft spheres are at first firm and glossy, but they become wrinkled and shrunken as they age, somewhat like dried fruit. The firm skin encloses a translucent gel.

Growing rapidly, Nostoc algae balls are photosynthetic, making energy from the sun during their short lifespan. They have the ability to fix nitrogen in the soil.

Reproduction is by fragmentation. They can lie dormant, invisibly, for many years, appearing abruptly when enough moisture arrives. They can grow in soil, on moist rocks or in freshwater, and are widespread worldwide, from hot dry deserts to polar regions. Surprisingly, this species is officially classified as a blue-green algae, despite it being completely different in appearance to the nuisance occurrences of blue-green algae in lakes and reservoirs.

A Courier article earlier this month mentioned a reduction in numbers of kookaburras, and expressed the desirability of baseline counts of these iconic birds. This followed a report by Birdlife Australia expressing concern about an apparent decline in kookaburra numbers in eastern Australia.

This matter was mentioned at the latest meeting of Birdlife Ballarat, where none of the 30 or more members present had noticed any decline. One member reported recently seeing 11 kookaburras between Smeaton and Campbelltown.

More research needs to be done to confirm the apparent decline, and to determine why it is occurring. Local population counts now will be a desirable start to any study, so that similar counts can be undertaken in years to come to determine what changes have occurred.

Kookaburras use holes in trees for nesting, and these are always in short supply, being also used by parrots, cockatoos and other birds. Perhaps the lack of hollows is starting to affect the kookaburra population.

White ibises are back at Lake Wendouree and they seem to be nesting on the islands. Is it likely they are actually nesting now, in the middle of winter? The nesting islands do not even have any leaves on them yet.

D.A., Winter Valley.

Yes, the white ibises have returned and they are indeed nesting already. This is their usual behaviour here at Lake Wendouree, despite the current mid-winter conditions. Their nesting season seems very long, starting in July and continuing through until at least early summer.

Two or three eggs are laid, and incubated for three weeks or more, with the chicks remaining in the nest for seven weeks. Eggs are laid from July to about November, so it is likely that these first nests are earlier than most, with many pairs waiting longer before they start.