Learn Hardcore Indonesian: Burung itu kembali ke sarang di pohon dekat rumah. - That bird returns to the nest in the tree near the house.

So burung itu tells the listener that this is a specific, known bird, not just any bird.
If you said only Burung kembali ke sarang…, it would sound more like “A bird returned to the nest…” or a generic statement about birds, depending on context.

What is the difference between kembali and pulang? Could I say Burung itu pulang ke sarang?

Both kembali and pulang involve the idea of going back, but their usage is a bit different:

kembali = to return, to go back (neutral, general)
- Burung itu kembali ke sarang.
  The bird returned to the nest. (neutral statement)
pulang = to go back home, to go back to one’s place of origin
It has a “home” feeling.

Because a nest is the bird’s home, Burung itu pulang ke sarang is possible and sounds natural, especially if you want to emphasize “going back home.”
However, kembali is slightly more neutral and is very common in narrative descriptions.

Why is it kembali ke sarang and not kembali di sarang?

This is about the difference between ke and di:

ke = to, towards → shows movement / direction
di = at, in, on → shows location / position

So:

kembali ke sarang = return *to the nest* (movement)
di sarang = at / in the nest (location)

In the sentence, the bird is moving back to the nest, so ke is correct:
Burung itu kembali ke sarang… = The bird goes back to the nest.

How does di pohon dekat rumah fit into the sentence? What exactly does it modify?

The structure is:

kembali ke [sarang di [pohon dekat rumah]]

So we have a nested noun phrase:

rumah = house
dekat rumah = near the house
pohon dekat rumah = the tree near the house
di pohon dekat rumah = in the tree near the house
sarang di pohon dekat rumah = the nest in the tree near the house

So di pohon dekat rumah is describing sarang (the nest), not the verb kembali.

If you wanted it to clearly describe the place of returning (not just the nest), in speech you’d add a pause, or in writing a comma:

Burung itu kembali ke sarang, di pohon dekat rumah.
→ The bird returned to the nest, (which was) in the tree near the house.

Without a comma, the safest reading is that the nest is in that tree.

Why is there no word for “it” as the subject? Why not Itu burung itu kembali… or similar?

Indonesian doesn’t require an explicit subject pronoun like English does.

English: It returned to the nest.
Indonesian: Burung itu kembali ke sarang…
(literally: Bird that/the returned to nest…)

Here, burung itu already functions as the subject.
Adding something like itu in front as an English-style “it” would be incorrect.

Subject pronouns like dia, ia, mereka, saya, kamu are only used when the subject is not already named or you want to refer back to someone/something already mentioned:

Burung itu terbang. Dia kemudian kembali ke sarang.
The bird flew. It then returned to the nest.

How do I know whether this means “the bird returned” or “the birds returned”? There’s no plural ending.

Indonesian usually doesn’t mark plural forms on nouns. Context does the work.

burung can mean bird or birds.
burung itu usually suggests a specific single bird, like “that bird / the bird”.
burung-burung itu clearly means “those birds / the birds (plural)”.

In your sentence:

Most natural reading: one specific bird = the bird returned…
If you really meant several birds, you’d typically say:
Burung-burung itu kembali ke sarang…

Could we use -nya and say ke sarangnya instead of ke sarang?

Yes, but it changes the nuance slightly.

ke sarang = to the nest (neutral; context decides whose nest)
ke sarangnya can mean:
- to its nest (the bird’s own nest), or
- to the nest (with -nya as a definite marker)

So:

Burung itu kembali ke sarang di pohon dekat rumah.
→ The bird returned to the nest in the tree near the house.
(We understand from context that it’s its own nest.)
Burung itu kembali ke sarangnya di pohon dekat rumah.
→ The bird returned to its nest in the tree near the house.
(More explicit about possession.)

Both are grammatical; ke sarangnya just emphasizes ownership/definiteness.

Why do we say dekat rumah and not dekat dengan rumah or di dekat rumah?

All of these forms exist; they differ in style and nuance:

dekat rumah
- Common, slightly shorter, often in noun phrases:
  pohon dekat rumah = the tree near the house
dekat dengan rumah
- A bit more explicit/formal; often when dekat is used like a verb/adjective:
  Pohon itu dekat dengan rumah. = The tree is near the house.
di dekat rumah
- Clearly emphasizes location:
  Ada pohon di dekat rumah. = There is a tree near the house.

In a noun phrase like pohon dekat rumah, the compact form dekat rumah is very natural:

sarang di pohon dekat rumah
= the nest in the tree near the house

If you said sarang di pohon di dekat rumah, it’s still correct, just slightly more wordy and with a tiny extra emphasis on “being at a location near the house.”

Could we also say sarang yang di pohon dekat rumah? What is the role of yang?

Yes, you could say:

Burung itu kembali ke sarang yang di pohon dekat rumah.

Here yang introduces a relative clause or modifier of sarang:

sarang yang di pohon dekat rumah
= the nest that is in the tree near the house

The meaning is very close to sarang di pohon dekat rumah. Differences:

Without yang (sarang di pohon dekat rumah)
- More compact; very normal in everyday Indonesian.
With yang (sarang yang di pohon dekat rumah)
- Slightly more explicit and sometimes a bit more formal or explanatory.

Both are grammatically correct and natural.
In many situations, speakers prefer the shorter sarang di pohon dekat rumah unless they need clarity.

Why is there no word like “is” in di pohon dekat rumah? In English we might say “which is in the tree…”.

Indonesian often omits a verb like “to be” when expressing location or simple descriptions inside noun phrases.

English: the nest that is in the tree near the house
Indonesian: sarang di pohon dekat rumah
(literally: nest in tree near house)

There is no separate word for “is” here. The preposition di already indicates a state of being located somewhere, so you don’t need an extra “be” verb.

You only need a verb when it adds meaning:

Sarang itu ada di pohon dekat rumah.
= The nest is (exists) in the tree near the house.
(ada adds the sense of “exist / there is”.)

How would I say that this happened in the past or will happen in the future? There’s no tense marker.

Indonesian verbs don’t change form for tense. Time is usually shown by time words or context.

To mark time, you can add words like:

tadi = earlier, just now
kemarin = yesterday
sudah = already
akan = will
nanti = later

Examples:

Past (just happened):
Tadi burung itu kembali ke sarang di pohon dekat rumah.
→ Earlier, the bird returned to the nest in the tree near the house.
Completed action:
Burung itu sudah kembali ke sarang di pohon dekat rumah.
→ The bird has already returned to the nest…
Future:
Nanti burung itu akan kembali ke sarang di pohon dekat rumah.
→ Later the bird will return to the nest…

Without any time marker, the sentence is time-neutral, and context decides whether it’s past, present, or future.

Could we move itu somewhere else, like Burung kembali ke sarang di pohon dekat rumah itu? What changes?

Yes, moving itu changes what is being specified:

Burung itu kembali ke sarang di pohon dekat rumah.
- itu modifies burung → that/the bird (specific bird)
- The house is not specifically pointed out; just “a house” or “the house” from context.
Burung kembali ke sarang di pohon dekat rumah itu.
- itu now modifies rumah → that house / the house (over there / already known)
- The bird is not made specific by itu; it could be generic or defined by context.

So:

If you want to highlight which bird, use burung itu.
If you want to highlight which house, use rumah itu.