[Hildy]

I don't know...that's pushin it a bit, don't ya think? I axed the duck, but I don't think I'm gonna pull that one, yet.

[Slings and Arrows]

Technically, he's right, at least for silver and purple. All those examples are single rhymes; i.e., only the last syllable rhymes. AFAIK, there are no double rhymes (e.g., network-fretwork, mining-pining) for silver and purple.

[8mmMauser]

More on ducks and quacks:

I note tests are done on domesticated ducks in barnyard or lab conditions. However some of us familiar with wild ducks can note wild ducks and environment are substantially different in many respects.

A drake has a very deep quack and it is very hard to track his origin, whereas the hen which may be calling him in is easier to pinpoint. I can not recall an instance in fifty years of stalking these beasts where an echo were possible.

On the other hand I can't recall where I left my glasses either.