Counter modifying noun with という

Question

... 何百というふくろうが四方八方に飛び交う光景が見られました。
You could see the sight of hundreds of owls flying in every direction.

I'm intrigued by 何百というふくろう. Why is という used here?

I get very confused when it comes to numbers and counters in Japanese. Why could it not be just

何百のふくろう?

Or, maybe since we're counting birds, it should be

何百羽のふくろう?　

Or even, adverbially,

ふくろうが何百飛び交う.

Which among these examples is grammatical and what are the differnces of nuance between them?

Answer 1

何百というふくろう is very close to 何百ものふくろう:

• 数百(羽)のふくろう
  several hundred owls
• 何百(羽)ものふくろう
  hundreds of owls
• 何百(羽)というふくろう
  hundreds of owls

Although the latter two are translated into English the same way, I think the という version is a little more emphatic and literary, and often has a stronger connotation of "countless". I think it's best to remember this as a common grammar pattern rather than asking why. (Grammatically, 何百という is a relative clause that modifies ふくろう, so a super-literal translation is "owls to which one says hundreds".)

You can say the same thing adverbially:

• ふくろうが数百(羽)飛び交っている。
  Several hundred owls are flying about.
• ふくろうが何百(羽)も飛び交っている。
  Hundreds of owls are flying about.

In this pattern, 何 must be used with も, so 何百のふくろう and ふくろうが何百飛び交う are both ungrammatical. (You can say 何百のふくろう if you are asking "how many hundreds of owls?", though.)

EDIT: An important difference from ～もの is that you can use という only with 何. For example, you can say 83羽ものふくろう ("as many as eighty three owls") but not 83羽というふくろう.