Las cigüeñas migran en invierno.

Las is the plural definite article, meaning the.

In Spanish, it’s very common to use the definite article with plural nouns when talking about a whole class of animals or things in general. So:

• Las cigüeñas = storks / the storks

Even though English often drops the in general statements, Spanish often keeps it.

The ü is very important here.

In Spanish, gue and gui normally make the u silent:

• guerra sounds like geh-rra
• guitarra sounds like gee-tarra

But when Spanish wants the u to be pronounced in gue or gui, it adds a diaeresis: ü

So:

• cigüeña is pronounced roughly thee-GWEN-ya in much of Spain
• without the dots, the pronunciation would be different

The ü tells you to pronounce the u.

The letter ñ is a separate letter in Spanish, not just an n with a mark.

It represents a sound like ny in English words such as canyon.

So:

• ña sounds roughly like nya

In cigüeñas, that part sounds like nyas.

The written accent in cigüeñas shows where the stress goes.

The word is stressed on the güe syllable:

• ci-GÜE-ñas

Without the accent mark, the stress rules of Spanish would suggest a different pronunciation. So the accent mark helps show the correct stress pattern.

Migran is the present tense, third person plural form of migrar.

The subject is las cigüeñas, which is plural, so the verb must also be plural:

• la cigüeña migra = the stork migrates
• las cigüeñas migran = the storks migrate

It is not migraron, because that would be a past tense form: they migrated.

The infinitive is migrar, meaning to migrate.

This is a regular -ar verb. In the present tense:

• yo migro
• tú migras
• él/ella migra
• nosotros migramos
• vosotros migráis
• ellos/ellas migran

So migran means they migrate.

En invierno means in winter.

The preposition en is commonly used with seasons in Spanish:

• en invierno = in winter
• en verano = in summer
• en otoño = in autumn
• en primavera = in spring

So this is the normal and natural way to say in winter.

Both can exist, but en invierno is the usual general expression for in winter.

• En invierno = in winter, generally / during the winter season
• En el invierno de 2022 = in the winter of 2022

So in a general statement like this one, en invierno is the most natural choice.

Normally, it expresses a general fact or habitual action:

• Las cigüeñas migran en invierno. = Storks migrate in winter.

The Spanish present tense is often used for general truths, habits, and repeated actions, not only for actions happening at this exact moment.

That would sound unnatural in standard Spanish for this kind of general statement.

Spanish usually prefers:

• Las cigüeñas migran en invierno.

Using the article makes the sentence sound complete and natural when referring to storks as a species or group in general.

In standard Peninsular Spanish, a rough pronunciation is:

lahs thee-GWEN-yas MEE-gran en eem-BYEHR-no

A few key points:

• ci often sounds like thi in much of Spain
• güe sounds like gwe
• ñ sounds like ny
• j in invierno is not present, so nothing unusual there
• the stress is on güe in cigüeñas and on vier in invierno

A more Spanish-like rhythm would be:

Las cigüeñas migran en invierno.

Yes, but the original order is the most neutral and natural:

• Las cigüeñas migran en invierno.

You could sometimes move parts for emphasis, for example:

• En invierno migran las cigüeñas.

But that sounds more marked or stylistically different. For a learner, the basic order subject + verb + time phrase is the best pattern to follow.