Translation:I have two dogs, three cats and six chickens.
This sentence is clearly talking about pets, so the word for domestic fowl ought to be "hen". I wrote "I have two dogs, three cats and six hens" and it was accepted. Only at the stage when the meat is presented on a plate as food, does it become "chicken", and no plural in such a case. Likewise a pig becomes "pork" and a cow becomes "beef". However chicken is widely used those days for both, rightly or wrongly.
Maybe in other Germanic languages, but not in English. The only such plural I can think of is child-children. Most plurals are just -(e)s. Chick is just a short form like photo, phone, fridge and so on. I also suspect "chick" comes from the Spanish "chica", which means "girl".
Chick does not come from Spanish. It wouldn't make sense. It's derived from Old English, which obviously wouldn't have encountered modern Spanish (either geographically or chronologically speaking). Children is in fact a double plural that derives from the Old English neuter noun (ċild) whose plural was ċildru. The final vowel in the plural was lost when Middle English came about (childer). Somehow, it was pluralised further based on the pluralisation rule back then (-en) and so 'children' was born. Another word that shares the same plural ending is the word 'brethren' - which was the plural of brethere (brother).. but again.. it's double pluralised in Modern English based on the -s rule to brethrens (mistakingly.. but its usage can be found in everyday life). Beauty of word evolution.
Thank you for this interesting information. Actually I meant possible Spanish origin of "chick" in the sense of "girl", not in the sense of "fowl", which is obviously much older and firmly Germanic.
'As slang for "young woman" it is first recorded 1927 (in "Elmer Gantry" [by Sinclair Lewis]), supposedly from African-American vernacular. In British use in this sense by c. 1940; popularized by Beatniks late 1950s.' -- Etymonline
One topic Duolingo doesn't cover is style. Notice the missing Oxford comma. Most English style guides (Chicago, AP, APA) recommend it, even though it's not "wrong" to not use it. Does the Italian language have something similar to these style guides, or even better, something similar to Garner's Modern English Usage?