How can you make number one disappear by adding something to it?

What does this simple rebus mean?

You can hear me, but you can't touch or see me.

What am I?

Can you Find and name the hidden bird in the picture below ?

I have branches, but no fruit, trunk or leaves. What am I?

Can you decipher the below rebus?

PBLUESAISNUERSES

What number does the below three word/phrase identify and why?
1. Deck
2. Year
3. Singing in the Rain

Our product and our sum always give the same answer. Who are we?

John: "Hi Teacher, What is your favourite movie ?".
Chemistry Teacher: "Indium Cerium Platinum Iodine Oxygen Nitrogen".
Ten seconds later... John replied I got it.

Do you?

It spends most of its day eating white, but when it’s quick enough, it gets to eat fruit and sometimes some blue things. It’s in a dark room, where the walls are blue, it runs from a ghost that roams the halls and haunts it all the time. What is it?