Nature Notes | ‘Lakeweed’ role key in aquatic environment

Lake Wendouree’s ‘lakeweed’ (water-milfoil) is often considered a problem, but it is actually an important part of the lake’s ecosystem, contributing significantly to the good water quality.

RESPITE: Hardheads and black ducks on a carpet of lakeweed at Lake Wendouree. A range of birds use the mats for a variety of purposes.

RESPITE: Hardheads and black ducks on a carpet of lakeweed at Lake Wendouree. A range of birds use the mats for a variety of purposes.

Often overlooked are the effects it has on reducing the erosion of the sediment at the bottom of the lake, its positive effects on oxygenating the water, the shelter it provides for fish and numerous smaller aquatic creatures, and the food and shelter it provides for waterbirds.

While species of birds feeding directly on water-milfoil are relatively few, they include important species such as the black swan, blue-billed duck, coot and musk duck. These waterbirds may not actually favour it, but they use it regularly.

Water-milfoil is a native perennial plant, anchoring itself in the mud and growing to the surface where its insignificant flowers appear in summer. Like lawn grasses, its aim is to grow to flowering and seeding, and so – again like lawn grasses – cutting is required if it is to be prevented from reaching that stage.

When the lake’s water-milfoil reaches the surface, it forms ‘carpets’ that are much-used by waterbirds. Ducks, coots and grebes are often seen feeding within these carpets of lakeweed, and other species use the anchored lakeweed as calmer resting places away from waves. 

Some of the scarcer ducks such as shovelers, teal and pink-ears are attracted to these resting sites, and visiting ducks find security there while shooting occurs elsewhere in the district.

Cutting of the water-milfoil has increased substantially since the lake refilled. This reduces areas of surface-level lakeweed and other plants available for waterbirds to use for feeding and resting. A few species (grebes, for example) also make their nests on these mats of living surface vegetation.

A lakeweed-cutting program has been formulated and birds have been considered in this. However, bird-observers – and surely the birds themselves – would prefer more surface lakeweed to remain, especially in the main nesting months of October to February. This is most important on the western third of the lake.

It should not be necessary to have the lake look ‘tidy’.

To assist making our lakeweed less-maligned, perhaps we should stop using the term ‘lakeweed’ and use its official common name of lake water-milfoil. To botanists it is Myriophyllum salsugineum.

Magpie Mooning

People with magpies living nearby may notice them warbling at night. Nocturnal warbling in August is a common magpie habit, accentuated when there is moonlight.