Mi sobrina se ríe cuando el pato picotea sus zapatos.

In modern Spanish, reírse is the most common way to say to laugh.

• Mi sobrina se ríe = My niece laughs / is laughing
• Reír without se does exist, but learners will much more often hear reírse for the general idea of laughing.

So in this sentence, se is part of the verb expression, not a separate word with a literal meaning like herself.

Because reírse de means to laugh at someone or something, while reírse on its own just means to laugh.

Compare:

• Mi sobrina se ríe. = My niece laughs.
• Mi sobrina se ríe del pato. = My niece laughs at the duck.

In your sentence, the niece is simply laughing when something happens, so de is not needed.

Spanish normally uses the short possessive before the noun:

• mi sobrina = my niece
• mis zapatos = my shoes

The longer form, like la sobrina mía, is possible but much less neutral and usually adds emphasis, contrast, or a special tone.

So mi sobrina is the normal everyday choice.

Because Spanish often uses possessive adjectives like mi, tu, su, nuestro where English would also use my, your, his, her, and so on.

• sus zapatos = his/her/your/their shoes

In this sentence, context makes it natural to understand that the shoes belong to the niece. However, sus can be ambiguous in Spanish, because it can mean:

• his
• her
• your (formal)
• their

If you want to remove all ambiguity, you can say:

• los zapatos de mi sobrina

That is clearer, but slightly heavier than sus zapatos.

Grammatically, sus is ambiguous, so yes, in theory it could. But context makes that interpretation unrealistic here.

A duck wearing shoes is unusual, so a native speaker will naturally understand sus zapatos as the niece’s shoes.

If a writer wanted to be absolutely precise, they could say:

• Mi sobrina se ríe cuando el pato picotea los zapatos de mi sobrina.

That is clearer, but less elegant because it repeats mi sobrina.

Because this sentence describes a habitual or general situation:

• Mi sobrina se ríe cuando el pato picotea sus zapatos.
• My niece laughs when the duck pecks at her shoes.

Both verbs are in the present because this is like a repeated scene or a general truth.

Spanish often uses:

• present + cuando
  • present

for things that regularly happen.

If you were talking about a future event, Spanish often uses the present after cuando too:

• Mi sobrina se reirá cuando el pato picotee sus zapatos.

Here the main clause is future, and the cuando clause uses the subjunctive because it refers to a future event not yet realized.

Picotear specifically suggests pecking, especially the repeated pecking action of a bird using its beak.

• picar can mean to sting, bite, prick, or peck depending on context
• picotear gives a more vivid bird-like image

So el pato picotea sus zapatos sounds very natural because ducks peck with their beaks.

It can also suggest repeated little pecks, not just one single touch.

The accent mark shows the correct stress and helps indicate that í and e are pronounced separately.

So ríe is pronounced in two syllables, roughly:

• RI-e

Without the accent, Spanish spelling rules would suggest a different pattern.

This same idea appears in forms of reír such as:

• río
• ríes
• ríe

The accent helps preserve the correct pronunciation.

It is normally pronounced as two syllables:

• rí-e

A rough English approximation is REE-eh, but said smoothly.

This is not like a single-syllable English sound. The accent on í helps show that the vowel sequence is split.

Spanish uses articles more often than English.

Here, el pato means:

• the duck

Even if English might sometimes say when a duck pecks at her shoes, Spanish often prefers a definite article when the speaker has a specific duck in mind or when the situation is understood from context.

So el pato sounds natural and complete.

Because the sentence describes something that happens regularly or characteristically.

This kind of present tense can mean:

• a habitual action
• a repeated situation
• a vivid general scene

So the sentence is not limited to one exact moment. It suggests something like:

• Whenever the duck pecks at her shoes, she laughs.

If you wanted a one-time past event, you would change the tense:

• Mi sobrina se rió cuando el pato picoteó sus zapatos.

The given word order is the most neutral:

• Mi sobrina se ríe cuando el pato picotea sus zapatos.

But Spanish allows some flexibility for emphasis. For example:

• Cuando el pato picotea sus zapatos, mi sobrina se ríe.

This has the same basic meaning, but it puts the when clause first.

You could also move elements around for style, but the original version is the most straightforward for learners.

Yes, in some contexts Spanish can prefer an indirect object plus article:

• El pato le picotea los zapatos.

This literally looks like The duck pecks at her the shoes, but in natural English it means The duck pecks at her shoes.

Spanish often does this with things closely connected to a person. So both patterns are possible:

• el pato picotea sus zapatos
• el pato le picotea los zapatos

The version with sus zapatos is very clear and beginner-friendly. The version with le is also very natural Spanish, especially in everyday speech.

It can mean either, depending on context.

Spanish present tense often covers both:

• she laughs
• she is laughing

In this sentence, because of cuando, the most natural interpretation is usually habitual:

• she laughs when...

But in the right context it could also describe what is happening right now:

• She is laughing when/as the duck pecks at her shoes

So the Spanish present tense is a bit broader than the English simple present.