Avifaunal sexual dimorphism

… or, the difference between girl birds and boy birds.

Golden Whistler (dimorphic)

The visual difference between male and female birds is very obvious in some species. The sombre grey tones of the female Golden Whistler are so completely different from the visually striking gold, black and white of the male.

Chestnut Teal (dimorphic - and the female has two legs😊)

The female Chestnut Teal has mottled brown feathers with a grey edge, a pale white throat patch, and lacks the iridescent green head of the male.

When the sexes are visually different in the bird world, it is mostly the male that is more colourful or at least visually brighter than the female (but not always – see later). Sexual dimorphism is the condition where different sexes of the same species exhibit differences in form, size, colour or structure. Sometimes the differences can be very minimal or subtle, and easily missed.

Crested Pigeon (monomorphic but some males might have a longer crest)

About half the world’s birds exhibit sexual dimorphism. The other half are monomorphic – the sexes are similar. Field guides will often describe monomorphic species as “sexes are similar” or sometimes, “sexes are similar, females duller”. In some field guides, no attempt is made to distinguish between male and female monomorphic species, just ‘adult’ and ‘juvenile’ differences might be explained.

Large-billed Corella (monomorphic)

A very few species of birds exhibit reverse sexual dimorphism (RSD) that is, the female is visually more colourful/brighter than the male.

Eclectus Parrot - Moonlit Sanctuary (reverse sexually dimorphic)

The Eclectus Parrot from Cape York Peninsula is a reverse sexually dimorphic species. The male is uniform emerald green with scarlet underwings. The female is a striking scarlet and blue bird.                                                                                                       

 

 

 

Sweet Chestnut

The Hundred-horse Chestnut (Wikipedia) is a Sweet Chestnut tree in Sicily that estimated to be between 2,000 and 4,000 years old. Almost at the beginning of the walking track in Golden Whistler Reserve there is a much younger version. At the moment – autumn – this tree is full of fruit.

The Sweet Chestnut, Castanea sativa, is native to Europe, Asia and Africa. Its true origin is thought to be Türkiye and/or the Caucuses but is now naturalised in many countries around the world.

The spiny fruit contains the nuts that are a favourite food raw, roasted or processed into a flour. Sweet Chestnuts are high in fibre and low in fat. They are gluten free and are rich in vitamins and antioxidants. The wood is valuable too – it is durable and resistant to rot.

There are hundreds of chestnut growers in Australia. About 75% of Australia’s chestnuts come from orchards in north-east Victoria. The tree was probably introduced to this country with the arrival of migrants for the 1850s gold rush.

Please note:

Sweet Chestnuts are edible, but Horse Chestnuts are poisonous (Plantura Magazine UK). The sweet chestnut fruit is brown when ripe and has numerous long bristly spines. It contains two to three nuts at a time, which are fairly small, flattened and triangular.

The Horse Chestnut fruit is thick and green, with small, short, more widely spaced spikes, and generally contain only one larger, rounded nut.

 

 

Australian Gypsywort

Australian Gypsywort, Lycopus australis, or Bugleweed, or Water Horehound, is an erect perennial herb that grows in moist to wet places around swamps, bogs and wetlands. It is a useful plant for binding the soil and providing food and habitat for a range of insects, frogs, etc.

Lycopus australis is native to Australia, quite common around wetlands in Victoria.  In Tasmania, Australian Gypsywort is a listed as ‘endangered’ in the Threatened Species Protection Act 1995. Good native nurseries often have Australian Gypsywort available for home gardeners to use in wet areas, frog ponds, etc.

There were several healthy populations of Australian Gypsywort at Thomas Maddock Reserve during a recent bird survey.