У птенца дрожало одно крыло, поэтому мы позвонили в центр помощи животным.

In Russian, у + genitive is very often used to express possession or something happening to / with someone.

So:

• У птенца дрожало одно крыло
  literally: At the chick, one wing was trembling
• natural English: The chick had one wing trembling / One of the chick’s wings was trembling

Here, птенца is in the genitive singular because it follows у.

This is a very common Russian pattern:

• У меня болит голова = My head hurts
• У собаки сломана лапа = The dog has a broken paw
• У ребёнка температура = The child has a fever

So Russian often avoids a direct equivalent of English the chick’s wing and instead uses this у + genitive structure.

Because the verb agrees with крыло, which is:

• neuter
• singular
• nominative

So the past tense form must also be neuter singular:

• крыло дрожало

Russian past tense agrees in gender and number with the subject:

• крыло дрожало — the wing was trembling
• лапа дрожала — the paw was trembling
• хвост дрожал — the tail was trembling
• крылья дрожали — the wings were trembling

Even though птенца appears near the beginning, it is not the grammatical subject here. The subject is одно крыло.

Одно крыло literally means one wing.

In this sentence, it implies one of the chick’s wings. The use of одно highlights that it was only one wing, not both.

Compare:

• У птенца дрожало крыло
  = The chick’s wing was trembling / A wing was trembling
• У птенца дрожало одно крыло
  = One wing was trembling / Only one wing was trembling

So одно adds a bit of specificity and emphasis.

Also, одно is the neuter form of one, matching крыло:

• один — masculine
• одна — feminine
• одно — neuter

Because крыло is the grammatical subject of the clause.

In У птенца дрожало одно крыло, the thing actually doing the action of trembling is одно крыло.

So:

• одно крыло = nominative subject
• дрожало = verb agreeing with that subject
• у птенца = an added phrase showing whose wing it is

This can feel unusual to English speakers because English might think of the chick as the main subject. But in Russian, the structure is built around the wing as the subject.

Yes, absolutely.

Russian often omits personal pronouns when they are understood from context. So both are possible:

• ...поэтому мы позвонили в центр помощи животным
• ...поэтому позвонили в центр помощи животным

Including мы makes the subject explicit:

• maybe for clarity
• maybe for slight emphasis: we called

Without мы, the sentence still sounds natural and often even more typical of spoken or written Russian if the subject is already clear.

Because позвонили is the perfective past tense, and it describes a completed single action: they made the call.

• позвонить = to call, to make a phone call once/completely
• звонить = to call / be calling, usually imperfective

Here the sentence tells us what they did in response: they called the center. That is a completed event, so позвонили fits well.

Compare:

• Мы позвонили в центр.
  = We called the center.
  completed action

• Мы звонили в центр весь день.
  = We were calling / called the center all day.
  process, repeated attempt, or duration

So позвонили is the natural choice here.

Here в means to / into, showing direction toward a place or institution, so it takes the accusative case.

• позвонить в центр = to call the center

For an inanimate masculine noun like центр, the accusative singular looks the same as the nominative singular:

• nominative: центр
• accusative: центр

So the form does not visibly change, but grammatically it is accusative here.

This use may feel odd because in English we say call a center, without a preposition. In Russian, with institutions and phone calls, звонить / позвонить в is common.

This phrase breaks down like this:

• центр = center
• помощи = of help / assistance
• животным = to animals

So literally:

• центр помощи животным = center of help to animals
• natural English: animal help center, animal rescue center, center for helping animals

The cases are:

1. помощи — genitive singular
   because it depends on центр:
   центр чего? = center of what? → помощи

2. животным — dative plural
   because помощь normally takes the dative:
   помощь кому? = help to whom? → животным

So the internal grammar is:

• центр
  of
• помощи
  to
• животным

This is a very useful pattern in Russian noun phrases.

Because the noun помощь governs the dative case.

Russian asks:

• помощь кому? чему?
  = help to whom? to what?

So:

• помощь животным = help to animals
• помощь детям = help to children
• помощь пострадавшим = help to the injured

Even though English often uses animal as an adjective in phrases like animal rescue center, Russian keeps the underlying relationship clearer: it is a center for helping animals, so животным stays in the dative.

Поэтому means therefore, so, or that’s why.

It connects the two parts of the sentence:

• У птенца дрожало одно крыло
• поэтому мы позвонили в центр помощи животным

So the second clause is presented as the consequence of the first one.

A very natural translation would be:

• One of the chick’s wings was trembling, so we called an animal rescue center.

It is a common connector in Russian for cause-and-result.

Yes, it could be rearranged, because Russian word order is flexible. But each version has a slightly different emphasis.

The given sentence:

• У птенца дрожало одно крыло, поэтому мы позвонили...

This sounds natural and starts with the chick as the topic.

Other possible orders:

• Одно крыло у птенца дрожало...
  puts more emphasis on one wing
• Мы позвонили в центр помощи животным, потому что у птенца дрожало одно крыло.
  restructures the whole sentence as We called... because...

So the original order is not the only grammatical one, but it is very natural and easy to process.

All of those can work depending on context.

Птенец means a young bird. In English, the best translation depends on style and situation:

• chick — common, simple, natural in many contexts
• baby bird — very clear, especially for learners
• nestling — more specific, a young bird still in the nest
• fledgling — a young bird that has begun to grow flight feathers or leave the nest

So in this sentence, chick or baby bird is usually the safest natural translation unless the broader context tells you something more specific.