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The Pacific Black Duck (Anas superciliosa), in the Family Anatidae, is one of the most common native dabbling Ducks. It can be found all across Australia, typically in association with water sources, i.e. ponds, lakes, rivers, wetlands, and is frequently seen in urban waterways.
The Mallard (Anas platyrhynchos) was introduced to Australia in the 1860s and has been spreading slowly across the south east and other populated areas.
These closely related species have similar habits and occupy the same environments. Where they are both present, the Mallards will breed with the local Pacific Black Ducks. With several broods each year of 7 to 12 ducklings, and 20% reaching adulthood, the Mallard genes quickly make their way into the local Pacific Black Duck population.
The New Zealand population of Pacific Black Ducks, locally known as Grey Ducks, is generally considered to be so extensively hybridized with Mallards, that the pure Grey Duck is considered exceptionally rare, bordering on extinct.
So when you spot what appears to be a Pacific Black Duck, how can you tell if it is actually a hybrid with Mallard genes? Being able to identify which are hybrids is a great skill to have. In urban areas you’ll quickly discover just how far ranging this issue already is, and you can help to spread awareness.
First up are the hybrids that have very distinct and obvious traits. Even to the untrained eye, the first impression will be that something ain’t right.
The easiest hybrid trait to recognise is the colour of the legs and feet. Mallards have bright orange legs, whereas PBDs have typically grey/green, dusky brown or tan. Hybrids can have legs bright orange like the Mallards. Some will have a duller orange. In photographs, lighting conditions can affect how orange the legs look. In dim light they can look darker. In early or evening warm sunlight, they can look more orange than usual.
A patchy bill is also quite easy to recognise, assuming you can get close enough to see. A pure PBD will have an evenly coloured grey/green bill. A hybrid may have an orange, yellow, or green bill often with patches.
Hybrids may also show lighter feathers and/or feathers with broad buff fringes. A pure PBD will have narrow buff fringes. This trait is a little more difficult to identify, in that it requires some observation experience of both PBDs and hybrids. This can be difficult in urban areas where many are hybrids showing varying degrees of this trait. (Also note below the ducklings show hybrid traits with varying facial markings).
There are several features on the head that may indicate a hybrid. A pure PBD will have a dark stripe from the gape to below the eye. (This stripe is not quite as dark/solid as the stripe through the eye). Hybrids may have this stripe entirely missing, a faint or wider stripe, or partial stripe that doesn’t extend the full distance. Additionally the crown of a PBD is typically quite dark. A streaked or paler crown may suggest a hybrid, however this may also be present on juveniles.
The final few visible traits that may be present in hybrids are a little more difficult to spot. In part because they are a matter of ‘degree’ where observation experience is necessary, or they are only visible in certain circumstances.
The coloured patch (speculum) on the wing of a pure PBD is iridescent green, bordered fore and aft by black. A hybrid may have an iridescent blue patch, however seeing this will depend on lighting angle. A hybrid may also show a white fore and aft trim, reminiscent of the Mallard which has a wide white trim.
Finally, the hybrids may show streaking / mottling extending up into the cream face patches and the tail feathers may be curled, as is typical of the Mallard.
Additionally, there are a sometimes atypical combinations of traits that indicate hybridisation, possibly with one of the domestic varieties of Mallard.
Further to the above, there is no guarantee that a hybrid will show any obvious visible traits. In urban areas where Mallards have been present for some time, it’s possible that all the local Pacific Black Ducks now have some Mallard ancestry.
There are a couple of other feral ducks that you may spot, particularly in urban areas. There are a few varieties of domestic Mallards that come in a range of colours. In fewer numbers, feral domestic Muscovy ducks (Cairina moschata) may be seen. These are quite easy to identify with their red warty faces.
To give some idea of the scale of the hybrid issue, almost all the above images have been recorded in the metropolitan areas in South Australia.
Considering all the above, let’s revisit the first photo in this post. Now how many pure Pacific Black Ducks can you see? Knowledge is the key to seeing the issue that’s been right in front of us the whole time.
If you’d like to help slow the spread of hybridisation, you can start by spreading the knowledge. Photograph any potential hybrids or feral Mallards you see and upload the images to iNaturalist. These records are synced with the Atlas of Living Australia and become records that can be utilised by scientists for research.
Below are a few links to further images, records and information on the issue of Pacific Black Duck x Mallard hybrids.
All iNaturalist records across South Australia for PBD x Mallard hybrids. Review the records and see if you can spot the hybrid traits. Some of the records have explanations in the comments.
All iNaturalist records across South Australia for pure Pacific Black Ducks. It’s worth noting that many of these records may yet be shown to be hybrids. See if you can spot any that might need correcting.
Mallards & hybrids in Australia iNaturalist Project, pooling over 3,000 records of feral Mallards and hybrids across Australia.
Mallard and Hybrid Ducks in Tasmania Facebook group. A wealth of information on hybrids.