"You can hear the birds."
Translation:שומעים את הציפורים.
You hear the birds - אתה שומע את הציפורים In the English sentence "You" is used as the "generic you". This grammatical construction does not exist in Hebrew (as you can see from here, the third plural from is used to express this meaning).
It's also possible to translate the English sentence as "אתה יכול לשמוע את הציפורים". In this case "You" is used as the second person singular pronoun, and not as the generic one.
I can think of a few translations.
For the general you: אפשר לשמוע את הציפורים.
For the plural you: אתם יכולים לשמוע את הציפורים.
For the singular you: אתה יכול לשמוע את הציפורים.
Only within context שומעים את הציפורים might be acceptable (like in "It is so quiet here that you can hear the birds" which can be translated to כל כך שקט כאן ששומעים את הציפורים) but even in this case אפשר לשמוע את הציפורים would be more natural.
I'm a native Hebrew speaker, too, has been living in Israel for all my 47 years; FWIW it sounds perfectly natural to me. Indeed, it requires some context, but that context can be no more than תקשיב, שומעים את הציפורים! Or, Q & A: מה אתה אוהב בפארק הזה? שומעים את הציפורים. I agree that אפשר לשמוע is equally natural, but I don't think it's more natural.
Just checked in Even Shoshan: יכול is a verb, and the future יוכל actually appears in the bible (1 Samuel 3:2).
The thing about this verb that throws native speakers off is that it's past tense, properly, irregularly has the /o/ like the present. So you should say יכולתי - most speakers have no problem with that - and, in 3rd person singular - יכול, identical between past and present. That is unbearable to most speakers. Less educated ones might say יכל /yakhal/, and extend it to יכלתי /yakhalti/. More educated speakers will add היה, only to the 3rd person singular: הוא היה יכול לשמוע את הציפורים. That, in turn, might draw some reflective speakers or learners to think that יכול is an adjective.
The problem we're encountering is actually with English, because we can say in English "one" or "you" and they have the same referent. Hebrew uses יכל also but in this impersonal construction when we render it into English "can" works sometimes. It's really an issue with English. One hears birds [here] or one can hear birds [around here or over there] or we hear birds or we can hear birds or you hear birds [in these parts].
Yes, as you wrote it. You is אתה and you are missing the direct object marker את before the birds, so it would be אתה יכול לשמוע את הציפורים. However, this lesson is trying to teach us "impersonal you", which omits the pronoun and has the verb in the plural - שומעים את הציפורים.