Learn Hardcore Malay: Di sangkar sebelah, ada beberapa burung kecil yang sangat bising. - In the next cage, there are several small birds that are very noisy.

So di sangkar sebelah is literally “at the cage next to (us/this)” or “in the cage beside [something implied by context]”.
Sebelah is often used to mean the next one along, the neighbouring one, or next door.

Why di and not dalam before sangkar?

di is a general preposition for location: at / in / on.
dalam is more specifically inside.

You can say:

Di sangkar sebelah – focuses on the location at that cage (where those birds are).
Dalam sangkar sebelah – explicitly emphasizes inside the cage next door.

Both can be correct; in many contexts di sangkar sebelah is natural, because it’s already obvious the birds are inside the cage.

What is the function of the comma after sebelah? Is it necessary?

The comma marks a pause for a fronted location phrase:

Di sangkar sebelah, ada beberapa burung kecil…
= As for the cage next door, there are some small birds…

In speech you would naturally pause there. In writing, the comma is optional but common when you front a phrase like this. You could also write it without a comma in informal text, but with the comma is clearer and more standard.

What exactly does ada mean here? Is it the same as “have”?

In this sentence, ada is an existential verb, meaning “there is / there are”:

Ada beberapa burung kecil…
= There are some small birds…

Malay uses ada in two main ways:

Existence:
- Ada burung di situ. = There is a bird there.
Possession (have):
- Saya ada burung. = I have a bird.

The meaning is decided by the structure:

[Ada] + [thing] + [place] → there is/are
[Subject] + ada + [thing] → subject has

Why isn’t there a subject like “they” or “there” before ada?

Malay does not need a dummy subject like English “there” in “there are birds”.
You simply start with ada:

Ada beberapa burung kecil…
Literally: Exist some small birds… → understood as There are some small birds…

So in Di sangkar sebelah, ada beberapa burung kecil…, the subject is really “beberapa burung kecil”, and ada is the verb.

Why doesn’t burung have a plural ending, like birds?

Malay nouns generally do not change form for plural.
Plurality is shown by:

Context
Numbers / quantifiers (e.g. tiga = three, banyak = many, beberapa = several)
Sometimes reduplication: burung-burung = birds

Here:

beberapa burung kecil
= several small birds

Beberapa already shows it is plural, so burung stays in its base form with no plural ending.

Shouldn’t there be a classifier, like beberapa ekor burung kecil?

Malay often uses classifiers (measure words) for counting nouns, especially animals:

ekor = classifier for animals (literally “tail”)

So:

beberapa ekor burung kecil
is a very natural, slightly more explicit way to say several small birds.

However, in many everyday contexts, beberapa burung kecil (without ekor) is still understood and acceptable, especially in informal speech or when the meaning is obvious.
Including ekor is a bit more careful and textbook-like; omitting it makes the phrase shorter and more casual.

Can kecil come before burung, like in English “small birds”?

No. In Malay, adjectives normally come after the noun they modify.

Correct:

burung kecil = small birds / a small bird
burung besar = big bird

Incorrect:

kecil burung (ungrammatical in standard Malay)

So the normal order is:

[quantifier] + [classifier] + [noun] + [adjective]
e.g. beberapa ekor burung kecil

What does yang do in burung kecil yang sangat bising?

Yang introduces a relative clause (a describing clause) and works like “that / which / who” in English.

burung kecil yang sangat bising
= small birds that are very noisy

Structure:

burung kecil = small birds
yang sangat bising = that are very noisy

So yang links the noun phrase (burung kecil) to the describing clause (sangat bising).

Can yang be left out in this sentence?

No. In standard Malay, yang is needed to introduce this kind of relative clause.

burung kecil yang sangat bising = correct
burung kecil sangat bising = sounds like two separate pieces shoved together; it’s unnatural here if you mean “small birds that are very noisy”.

Without yang, burung kecil sangat bising would be interpreted more like a bare statement “small birds are very noisy” (and even then, you’d normally add something like itu or memang to sound natural).

What is the difference between sangat bising, terlalu bising, and amat bising?

All are intensifiers, but with slightly different nuances:

sangat bising
= very noisy
Neutral, standard, commonly used in both speech and writing.
amat bising
= also very / extremely noisy
Often feels a bit more formal or literary, though you do hear it in speech too.
terlalu bising
= too noisy (excessive, more than desirable)
This usually implies a negative judgment: the noise is too much.

So:

yang sangat bising = that are very noisy (strong description)
yang terlalu bising = that are too noisy (complaint/criticism)

Can bising be used for people or places, or only for animals/sounds?

Bising describes noise or noisiness in general, not just animals.

You can say:

Budak-budak itu bising. = The kids are noisy.
Kawasan ini sangat bising. = This area is very noisy.
Jalan raya itu bising. = That road is noisy (lots of traffic noise).

So burung kecil yang sangat bising fits the normal use of bising: birds that are making a lot of noise.

Do we need adalah anywhere in this sentence?

No. Adalah is typically used:

before a noun phrase or adjective phrase as a kind of copula in formal styles
(e.g. Dia adalah doktor. = He is a doctor.)

In your sentence, the verb is ada (existential there is/are), not a copula:

… ada beberapa burung kecil …
= there are some small birds…

Adding adalah here would be ungrammatical. You just use ada on its own.

Can the word order be changed to: Ada beberapa burung kecil yang sangat bising di sangkar sebelah?

Yes, that is also correct:

Ada beberapa burung kecil yang sangat bising di sangkar sebelah.

This version:

starts with ada (there are)
gives the noun phrase (beberapa burung kecil yang sangat bising)
then adds the location (di sangkar sebelah) at the end.

Meaning is effectively the same. The original:

Di sangkar sebelah, ada beberapa burung kecil yang sangat bising.

puts the location first as a topic, something like “As for the cage next door…”
Both word orders are natural; it’s mostly a matter of emphasis and style.

Is there any difference between di sangkar sebelah and di sangkar di sebelah?

Yes, there is a nuance:

di sangkar sebelah
= in/at the cage next door / the cage beside us
Here sebelah directly modifies sangkar (the next-door cage).
di sangkar di sebelah
= in the cage that is beside (something)
Literally “in the cage that is at the side”.
This sounds slightly more explicit, as if you’re saying “the cage that is over there next to [something]”.

In many everyday contexts they’ll be understood similarly, but di sangkar sebelah is shorter and more idiomatic when you mean the neighbouring cage / the one next to this one.