I find Mallard ducks very confusing - they can be patterned, darker or lighter, all white or all black, and even larger than normal or much smaller. What I find even more confusing is that they hybridize readily with the Pacific Black Duck (PBD), making it difficult to know if a PBD is a pure native or a Mallard hybrid.
These are notes to keep track of main identifying features of confusing ducks. Please comment if you have any extra hot-tips. I focus on Mallard x PBD because these are the main hybrids I see in Tasmania.
Pacific Black Duck
Identifying features of PBDs include grey bill, dark legs and feet, black lines through face (widest through eye) and a dark brown body with buff feather margins:
Image by fritzu from observation https://www.inaturalist.org/observations/25345332
Mallard hybrids
There are a number of physical variants that can be expressed in Mallard x PBD hybrids. These can be subtle to very obvious. These include:
Orange legs
Bright orange legs is a Mallard trait and is a very commonly expressed trait in hybrids. While PBD can have an orange hue, bright orange is distinctive of Mallard genes:
Image by Roy Lowry from observation https://www.inaturalist.org/observations/45056622
Discolouration of bill
Discolouration to bill is also indicative of Mallard genes. Bill discolouration can be any colour (i.e. not necessarily orange):
Left image by Graeme Rigg from observation https://www.inaturalist.org/observations/45241779
Right image by Athas from observation https://www.inaturalist.org/observations/72357925
Light feather colouration
Light colouring (lighter than normal for a PBD) is indicative of a Mallard x PBD hybrid. Some examples:
Light variant:
Left image by Catalina Tong from observation https://www.inaturalist.org/observations/39354902
Right image by Anna Lanigan from observation https://www.inaturalist.org/observations/25652293
Very light variant:
Left image by naturego1 from observation https://www.inaturalist.org/observations/61539055
Right image by Tamika Lunn (me) from observation https://www.inaturalist.org/observations/75140373#activity_comment_faaf79bc-df3c-4f6a-bd84-f0d3f53264b5
Light neck and breast:
Image by Geoffrey Cox from observation https://www.inaturalist.org/observations/13660337
Curly tail
Curly tails are another Mallard trait, and is a very commonly expressed trait in hybrids:
Image by Antoni Camozzato from observation https://www.inaturalist.org/observations/30089284
Non-uniform ducklings
Another sign of hybrids is that the ducklings have different markings. See above photo by Catalina Tong. Another example:
Image by Catalina Tong from observation https://www.inaturalist.org/observations/39354911
Pure Mallard
Physical features of mallards are enormously variable, so I won't include many photos of these. Northern Mallard males have a green head, white neck-ring, brown body and bright bills/legs. Females look similar to a PBD but very pale and without strong face markings. As mentioned, Domestic Mallards could range from anything between entirely black to entirely white. I tend to err that, if they don't look like anything else (including other domestic breeds) they're probably a Domestic Mallard. When looking at the many variations, watch for bright bill/legs and little curled feathers above the tail. The curled tailed in particular is diagnostic of a male Mallard.
Male:
Image by Allan Lugg from observation https://www.inaturalist.org/observations/66999481
Female (left):
Image by Bay Reeson from observation https://www.inaturalist.org/observations/63748297