kono su de saezutte iru tori wa suzume ni chigai nai.

The bird chirping in this nest must surely be a sparrow.

Breakdown of kono su de saezutte iru tori wa suzume ni chigai nai.

• は: topic particle
• で: location particle
• この: this
• いる: to exist (animate)

Questions & Answers about kono su de saezutte iru tori wa suzume ni chigai nai.

What is the basic structure of this sentence?

It breaks down like this:

この巣で = at/in this nest
さえずっている = is chirping
鳥 = bird
は = topic marker
雀に違いない = must be a sparrow

So the overall structure is:

[この巣でさえずっている鳥] は [雀に違いない]

In other words, the bird that is chirping at this nest must be a sparrow.

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How does さえずっている鳥 work? Why is there no word like that?

This is a Japanese relative clause.

In English, you say:

the bird that is chirping

In Japanese, the clause simply comes before the noun:

さえずっている鳥

Literally, this is something like:

chirping bird

or more naturally:

the bird that is chirping

Japanese does not need a relative pronoun like that, which, or who here.

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Why is で used after 巣 instead of に?