https://en.wikipedia.org/wiki/Duck says:

"Duck is the common name for numerous species of waterfowl in the family Anatidae. Ducks are generally smaller and shorter-necked than swans and geese, which are members of the same family."

"Ducks are sometimes confused with several types of unrelated water birds with similar forms, such as loons or divers, grebes, gallinules and coots."

#ducksOrNotDucks /1

So far, so good. That sounds simple - swans, geese, grebes and coots are NOT ducks. Got it.

[Grebes are apparently flamingos. But that's a different story].

But then we get onto taxonomy...

#ducksOrNotDucks /2

From Wikipeda/Duck:

".. the so-called 'true ducks' belong to the subfamily Anatinae, which is further split into a varying number of tribes.

The largest of these, the Anatini, contains the 'dabbling' or 'river' ducks ...

The 'diving ducks', also named for their primary feeding method, make up the tribe Aythyini.

The 'sea ducks' of the tribe Mergini are diving ducks which specialise on fish and shellfish and spend a majority of their lives in saltwater."

#ducksOrNotDucks /3

OK, let's see what it says about Anatinae: https://en.wikipedia.org/wiki/Anatinae

"The Anatinae are a subfamily of the family Anatidae (swans, geese, and ducks). Its surviving members are the dabbling ducks"

Dabbling ducks. Right.

But what about diving ducks and sea ducks which you just mentioned before...

#ducksOrNotDucks /4

"Much debate exists about the systematical status and which ducks belong to the Anatinae. Some taxonomic authorities only include the dabbling ducks and their close relatives...

Alternatively, the Anatinae are considered to include most "ducks", and the dabbling ducks to form a tribe Anatini within these."

Well that's clear then. Most "ducks". 😅

#ducksOrNotDucks /5

What about looking higher up, at the family Anatidae: https://en.wikipedia.org/wiki/Anatidae

[skipping section about duck penises.. no-one needs that]

"The systematics of the Anatidae are in a state of flux. Previously divided into six subfamilies, a study of anatomical characters by Livezey suggests the Anatidae are better treated in nine subfamilies.[clarification needed]"

So which is it, 6 sub families? 9 sub families? "Clarification needed", indeed.

#ducksOrNotDucks /6

Ah, it has a "Genera" section. All will become clear.. https://en.wikipedia.org/wiki/Anatidae#Genera

• Subfamily
• Subfamily
• Subfamily
• Subfamily
• Subfamily
• Subfamily
• Subfamily
• Tribe (?!!)
• Tribe
• Unresolved

.. so that's actually 7 subfamilies, 2 tribes and a whole mass of 'unresolved' species.

Just one of those subfamilies includes all swans *and* geese, contradicting what it said above.

#ducksOrNotDucks /7

So is everything else a duck?

Well, apparently an Egyptian goose is not a goose it's a shelduck. So if we allow shelducks as ducks, Egyptian geese are also ducks.

Tufted ducks are in subfamily Aythyinae, not Anatinae, which was described as "true ducks" above. So does that mean they're not real ducks?

Mergansers and eiders are in the same "tribe", so if an eider is a duck, so is a common merganser.

#ducksOrNotDucks /8

And let's not forget whistling ducks.

The Anatidae page also has this: ""Alternatively, the Anatidae may be considered to consist of three subfamilies (ducks, geese, and swans, essentially) .... with the swans separated as subfamily Cygninae, the goose subfamily Anserinae also containing the whistling ducks, and the Anatinae containing all other clades."

So... whistling ducks are actually geese? does that mean they're still ducks? Or not ducks?

#ducksOrNotDucks /9

Except.. just for kicks, that subfamily with swans and geese (Anserinae) doesn't include whistling ducks.

They have their own subfamily [Dendrocygninae].

Of course they do.

#ducksOrNotDucks /10

Conclusion: I don't know what a duck is any more.

Quack.

#ducksOrNotDucks /11

Appendix: there's more. Sorry.

If you go *up* a level in Wikipedia, to the order "Anseriformes", there's yet another different hierarchy of families, subfamilies and tribes.

https://en.wikipedia.org/wiki/Anseriformes#Systematics

Interestingly, this is the first one that actually makes sense!!

This has the subfamily Anatinae ("true ducks") split into 4 tribes: shelducks, sea ducks, diving ducks and dabbling ducks.

Where did this come from though?

Time to check the references..

#ducksOrNotDucks /12

It says: "The list below follows the AviList, which has accepted these revisions".

OK, let's look at that.

Well, it seems the AviList was pretty much started to try to resolve the mess that is Anatidae amongst all the various organisations that use bird taxonomies!

Maybe this will help.

Oh. No.

The AviList doesn't have "subfamilies" or "tribes" at all as far as I can see. These didn't come from there.

#ducksOrNotDucks /13

It also says:

"The systematics... is better resolved following the genetic analysis by Buckner et al. (2018)"

OK let's look at that.

These folks did come up with the four tribes. But their assignments don't match exactly what the Wikipedia page has. In fact, it looks like this is more like the Anatidae page itself which was so confusing.

It is quite recent.. but..

#ducksOrNotDucks /14

There's one more reference shoehorned in without context - Gonzalez et. al (2009).

Right! Now we're getting somewhere.

These people did gene sequencing and created a Bayesian inference tree on the results.

The tree they came up with *almost* matches the one in the Wikipedia page - I can see the page author has had to add a few bits they were missing, but I think this must be the true source.

hooray!

#ducksOrNotDucks /15

So why is this interesting?

Well, it gives the cleanest view of "Duck vs Not Duck" that I've seen anywhere.

If you simply say all "Anatinae" (as defined on this page) are ducks, and anything else is not a duck, this kinda works.

So: mallards, tufted ducks, teal, eiders are all ducks. We can all agree that, right?

Also: mergansers, shelduck and Egyptian geese (yes I know but it's not a goose) are ducks.

The true geese and swans (Anserinae) are *not ducks*.

#ducksOrNotDucks /16

Of course there's always the whistling ducks. Always.

They're not ducks. Except they're called ducks. But they're not, by that rule.

Nor are a few other more obscure birds which are called "ducks" that I've never heard of.

So I think I need to modify the rules a bit, for myself, at least.

#ducksOrNotDucks /17

What is a duck?

Keef's Law of Ducks v1.0:

Something is a duck, if at least one of the following applies:

1. It's a member of the four tribes of Anatinae (Tadornini - shelducks, Mergini - sea ducks, Aythyini - diving ducks, Anatini - dabbling ducks)

2. It's called a duck.

#ducksOrNotDucks /18

** DUCK-INDUCED MENTAL BREAKDOWN ENDS **