Over terrassen er der en lille rede, hvor en fugl kommer tilbage hver morgen.

Terrassen is the definite singular form of terrasse.

• terrasse = terrace / a terrace
• terrassen = the terrace

So over terrassen means above the terrace or over the terrace, not just over a terrace.

Here, over is a location word meaning something like above or over in space.

So over terrassen tells us where the nest is located: it is positioned above the terrace.

In English, depending on context, you might naturally say:

• above the terrace
• over the terrace
• sometimes even hanging over the terrace

Danish often moves a place phrase, time phrase, or other element to the front of the sentence for emphasis or to set the scene.

So instead of starting with Der er..., Danish can start with the location:

• Der er en lille rede over terrassen.
• Over terrassen er der en lille rede.

Both are possible, but the second one highlights the location first.

Because Danish main clauses follow the V2 rule: the finite verb must come in the second position.

In this sentence:

1. Over terrassen = first element
2. er = finite verb, so it must come second
3. der comes after that

That is why the order is:

• Over terrassen er der en lille rede

and not:

• Over terrassen der er en lille rede

This der is part of the very common Danish expression der er, which means there is / there are.

So:

• der er en lille rede = there is a small nest

Here, der is not really about a physical place. It is an existential dummy subject, similar to English there in there is.

Even when another phrase comes first, the construction still stays:

• Over terrassen er der en lille rede

Because rede is a common-gender noun in Danish, so it takes en in the indefinite singular.

• en rede = a nest

Then the adjective lille describes it:

• en lille rede = a small nest

So the full noun phrase is built like this:

• en
  • lille
    • rede

Lille is the normal Danish adjective for small in this kind of phrase.

With singular nouns, Danish commonly uses lille:

• en lille fugl
• et lille hus
• en lille rede

So even though Danish adjectives often change form, lille is a bit special and is very commonly used as lille in the singular.

Because hvor means where, and here it introduces a relative clause connected to a place.

The nest is being treated as a location:

• en lille rede, hvor en fugl kommer tilbage hver morgen
• a small nest where a bird comes back every morning

So hvor is natural because a nest is somewhere a bird can return to.

Yes, but the sentence would need to be built differently.

With hvor, Danish can express the location directly:

• en rede, hvor en fugl kommer tilbage hver morgen

If you use som, you normally need a preposition later:

• en rede, som en fugl kommer tilbage til hver morgen

Both are possible, but hvor is shorter and very natural when referring to a place.

Because hvor already supplies the idea of destination.

In other words, hvor already means something like to which place / where. So Danish does not need to add til here.

Compare:

• en rede, hvor en fugl kommer tilbage hver morgen
• en rede, som en fugl kommer tilbage til hver morgen

In the second version, til is necessary because som by itself does not express location.

Kommer tilbage means comes back or returns.

It is made of:

• kommer = comes
• tilbage = back

So this is a very common Danish expression:

• komme tilbage = to come back / to return

Because the sentence introduces a bird, not the bird.

• en fugl = a bird
• fuglen = the bird

Using en fugl makes the bird indefinite and unspecific. The speaker is not focusing on exactly which bird it is.

If it were a known bird already mentioned before, fuglen could be used.

Because Danish uses the present tense for actions that happen regularly or habitually.

The phrase hver morgen tells us this happens again and again, so the present tense is exactly what Danish normally uses:

• en fugl kommer tilbage hver morgen = a bird comes back every morning

This is just like English present tense for habits:

• She walks to work every day
• A bird comes back every morning

Because hver means every, and in Danish it is followed directly by a singular noun.

So:

• hver morgen = every morning
• hver dag = every day
• hver uge = every week

You do not add en after hver.

Yes. Hver morgen is a time expression, and it tells us when the bird comes back.

In Danish, time expressions like this often come near the end of the clause:

• en fugl kommer tilbage hver morgen

That placement is very natural and common.