The actual word "bird" is "sefor" (Deut 14:11). Another word that is being used is "ofe" "flyer" (Deut 14:19). See also Gen 7:14 where most of these are used together.
So I was thinking that the clue is somewhere here. Something to do with wings/feathers.
I.e. perhaps those birds that can't fly are considered clean? (Deut 14:11)
One may interpret that birds which cannot fly are inherently unclean. They would likely be considered movers (sherets), such as Lev 11:29, since they are not actually flyers (owph).
At the same time, Levt 11:29 talks primarily about locusts and such. It seems that insects are called flyers, while the birds are called "birds". I was more referring to the birds like chicken who can't really fly. The long distances that is...
But now when I am thinking about it, what about doves? Ducks? Its all so unclear :(
Both birds and insects are called flyers. 11:13 "from the flyer...the eagle...etc" , 11:21 "from every of mover of the flyer...the locust..."
Regarding doves, I don't know.
Regarding ducks, I'd think it's pretty likely they'd be unclean, considering there is a list of aquatic birds prohibited that we can translate from the LXX (11:18), if it's accurate anyway (I might translate it as flamingo, pelican, swans).
Personally I do not think that turkeys are "suspicious" so much, it is just that we do not have the awareness of the entirety of the translations for the birds in Hebrew. Therefore, turkeys and chickens I would say that I don't know if they are clean or not. If I was just to guess, I would guess clean, but that is knowing that I cannot make a truly legitimate guess without having further evidence from the language (maybe one of these prohibited and untranslated ones is a chicken or something, who knows). However, in regard to duck, I think duck is very likely unclean with the awareness that seems to be present (if swans are prohibited, there's not really much significant difference other than ducks being cuter, in my opinion).
Regarding the LXX, I might add that the meanings of the Greek words are not clear in many cases as well.
Turkeys look more like geese, although they can't swim. So perhaps this is why they are clean. Also, i think if chicken is clean, turkey also should be clean. I am not sure.
Ducks appear to me unclean as they are water birds, just like a swan. At the same time, ducks are not scavengers like seagulls. So maybe ducks are clean after all? Ducks have different beaks than swans.
I checked the LXX and I could not find any connection among the names mentioned there.
All scavengers are unclean.
I believe that I have a lack of knowledge to interpret in properly. All I know that there has to be some kind of connection, at least for "clean birds". In other words I am looking for a clue similar to a hoof split with cattle. Anyone?
Neither Leviticus or Deuteronomy seem to give such a generalization for birds, unlike all other types of animals (cloven hooves + rumination, fins + scales, legs hinged above for leaping). Birds treated uniquely in that respect in the Torah, and while it is possible that a generalization would exist, in all likelihood that generalization is simply going to be "Not [this type], not [this type], and not [this type]".
From my experience, when I do not understand Torah or think that "there is not enough information", it is usually me who is having a problem. So even though, at this time, there are no apparent clues, I most certainly believe that they are there and it is just a matter of time when someone will figure it out.