It is just like English sayings and phrases, there are Japanese sayings and phrases as well. It is called [kotowaza ことわざ].

Today’s kotowaza

鵜のマネをする烏　U no mane o suru Karasu

Few words for you.

U – Cormorant

Karazu – Crow

A crow imitating a cormorant.

Trying to ape your betters leads only to failure/Know your place.

Its origin

A crow which is not good at diving or swimming, tries to imitate a cormorant to catch a fish in water but 　drowned.

Its meaning

It won’t work out even if you copy someone with skills without thinking that you are capable of doing that particular things.

妹は将来歌手になりたいと、よくテレビの前で歌っている。私から見ると、鵜のマネをする烏だと思うが、すっかりその気になっているので、とてもそんな事いえない。

Imouto wa shourai kashu ni naritai to, yoku terebi no mae de utatte iru. Watashi kara miruto, u no mane wo suru karasu to omou ga, sukkari sono ki ni natte iru node, totemo sonnna koto wa ienai.

My sister wants to become a singer in future and often singing in front of a TV. In my view, I think she is u no mane o suru kara (Trying to ape your betters leads only to failure). But she has became so minded that I can not even tell her that.

arigato