‘We greet one another, smile or frown, depending on our mood. Animals, too, communicate, much to our surprise. Just like us, interaction among animals can be both verbal or non-verbal.’

We shortened it as:

Like us, animals too interact with one another via verbal or non-verbal method.

That’s it! We did not make any change in the meaning. What we have done here is just remove all other unnecessary content. Unnecessary content is a word or sentence whose presence or absence does not affect the main concept of the sentence.

Secondly, The sentence:

‘Singing is one way in which animals can interact with one another.’

is shortened as:

Singing is one of them.

Here, we avoid the repetition of the words, ‘interact with one another’.

Then, the sentence:

‘Male blackbirds often use their melodious songs to catch the attention of females. These songs are usually rich in note variation, encoding various kind of messages. Songs are also used to warn and keep off other blackbirds from their territory, usually a place where they dwell and reproduce.’

Becomes:

‘Male blackbirds sing to attract females and to keep away other blackbirds from their territory.’

Here, we used one word ‘attract’ instead of ‘catch the attention of’. Likewise, we removed all adjectives like melodious, encoded, etc.