Маленький воробей прыгает по земле у кормушки.

Because it agrees with воробей, which is:

• masculine
• singular
• nominative case

Russian adjectives change their endings to match the noun they describe.
So:

• маленький воробей = a small sparrow

If the noun changed, the adjective would change too. For example:

• маленькая птица = a small bird
• маленькие воробьи = small sparrows

Воробей is in the nominative singular.

It is the subject of the sentence — the one doing the action of прыгает.

A good basic rule is:

• the subject of a Russian sentence is usually in the nominative case

So in this sentence:

• воробей прыгает = the sparrow is hopping

Because the subject is singular:

• воробей = one sparrow

The verb прыгать changes to match the subject:

• я прыгаю = I jump
• ты прыгаешь = you jump
• он/она прыгает = he/she jumps
• они прыгают = they jump

So прыгает means he/she/it jumps / is jumping, which matches воробей.

Both can relate to ground, but they mean slightly different things.

• на земле = on the ground
• по земле = along the ground / over the ground / around on the ground

With verbs of movement like ходить, бегать, ползать, прыгать, Russian often uses по + dative to show movement over a surface or within an area.

So:

• прыгает по земле suggests the sparrow is hopping around on the ground, not just located there.

Because after по in this meaning, Russian usually uses the dative case.

The noun земля is a feminine noun, and its dative singular form is:

• земля → земле

So:

• по земле = along/on the ground

This is a common pattern:

• по дороге = along the road
• по улице = along the street
• по полу = across the floor

Because у means by, near, beside, and it requires the genitive case.

So:

• кормушка = feeder
• у кормушки = near the feeder

The noun changes form because of the preposition:

• кормушка → кормушки

This is very common in Russian:

• у дома = near the house
• у окна = by the window
• у двери = by the door

Here у means near, by, or beside.

So у кормушки tells you the location of the sparrow: it is hopping on the ground near the feeder.

Be careful: у can also mean possession in sentences like:

• у меня есть книга = I have a book

But in this sentence, it is purely a location word.

Russian present tense often covers both ideas:

• jumps
• is jumping

So прыгает can mean either, depending on context.

Russian does not usually need a separate form like English is hopping. The simple present form often does that job.

Yes, Russian word order is fairly flexible.

The neutral, straightforward order here is:

• Маленький воробей прыгает по земле у кормушки.

But you could change the order for emphasis, for example:

• У кормушки маленький воробей прыгает по земле.
• По земле у кормушки прыгает маленький воробей.

The core meaning stays similar because the case endings show how the words function.

Still, the original order sounds natural and neutral for a simple description.

Russian has no articles like English the and a/an.

So маленький воробей can mean:

• a small sparrow
• the small sparrow

The exact meaning depends on context.

Russian speakers understand definiteness from:

• context
• word order
• previous mention
• general situation

The dictionary forms are:

• маленький = small
• воробей = sparrow
• прыгать = to jump, hop
• земля = earth, ground, land
• кормушка = feeder

In the sentence, some words appear in changed forms because of grammar:

• земля → земле
• кормушка → кормушки
• прыгать → прыгает

No. In Russian, grammatical gender is not always the same as biological sex.

Воробей is a masculine noun as a vocabulary item, regardless of whether the actual sparrow is male or female in real life.

That is why the adjective is masculine:

• маленький воробей

This is about grammar, not necessarily biology.

Yes. Depending on context, маленький can be translated as:

• small
• little

In this sentence, both sound natural in English:

• a small sparrow
• a little sparrow

Usually, маленький simply describes size, but in some contexts little can sound more affectionate or vivid in English.