This case is called "complément de nom", ie "de" makes the kink between the main noun (family) and the nominal group (noun , + possibly adjective) which qualifies and specifies the main noun.
- un mur de pierre = a wall made of stone
- un livre de recettes = a book containing recipes
- un jour de bonheur = a day full of happiness
Most often in English, the two nouns are switch and there is no more "of": a stone wall, a recipe book, etc.
does this mean you can't encounter les familles des canards? I understand what you mean by a complement de nom, which seems to require that the main noun be a group category, like a gaggle of geese or a school of fish, or wheels of various cheeses--do these distinctions appear in French too, and this is the French way of expressing such distinctions?
if it were "jeunes" (young) it would be placed in front of the noun: une famille de jeunes canards (Age, in BAGS)
We have two (or more) ducks that have a family. The two (or more) ducks are yellow. But we cannot say that all the ducks in the family are yellow. Am I wrong to assume that "jeune" could have been placed with "une famille" to state that it is a yellow family? "Une famille jeune de canards"
"De" belongs to "famille" and not to "canards".
When you express the content, material, quantity or quality of something, you use "de" and the noun, in singular or plural, without an article.
- une bouteille de vin (a bottle of wine)
- une famille de canards (a family of ducks)
- une paire de chaussures (a pair of shoes)
- une table de bois (a wood table)