Quote:schazer:
in order for me establish whether something is a bird
it must first have a particular attribute that not all species have
there's no point counting how many toes an animal has if it doesn't have legs
similarly, there's no way I can determine an organism's bird-ness if it doesn't have ____________

btp:
Oh my god!
Birds are creatures that don't have a maned sloth!
BRILLIANT

schazer:
what have you found out about the maned sloth?
a final hint, for now, cuz i should sleep
you may, based on the way I tend to structure my answers, be tempted to order birds and not-birds taxonomically when trying to figure out the commonalities
this however is unhelpful

• Birdness is determined taxonomically, so "birds are species which _______" is a good way to think about it, yes.
  
• A hint: birdness is not predicated on scientific names. All species have a scientific name.
  
• Not all unicellular organisms are birds, nor are all prokaryotes. Probably. There's a chance that either of the above are not birds, and establishing as such is really goddamn time-consuming.
  
• I cannot without extensive research confirm whether or not all ferns are not birds.
  
• No species of anomalocaridid have the requisite feature to qualify as birds.
  
• As-yet undiscovered species lack the required feature to qualify as birds.
  
• Four toed hedgehogs are kind of birds? I'd feel bad calling it one way or another.
  

• Birds are not animals with sharp teeth or pincers.
  
• Birds are not the lesser extant species of their given subfamily.
  
• Birds are not organisms which have had their taxonomic classifications changed.
  
• Birds are not creatures that remind us of our limited time on earth.
  
• Birds are not species which hide for some time then reappear later.
  
• Birds are not species that exhibit sexual dimorphism.