There are three common approaches people take, and which one you take depends on your whims.

One common approach is to model them as very basic instinctual creatures. The birds will have a vague awareness of food and threats and such, but won't be able to communicate any complicated information due to their low intelligence scores. Complex requests won't be understood. This approach is good if you don't want to voice NPCs, want a more realistic approach, and

The second common approach is to model them as excitable toddlers. They have a decent amount of intelligence, can carry out a basic conversation, but can't understand complicated instructions and are pretty instinctual.

The third common approach is to model them as full NPCs, give them complicated histories and emotions, and use it as a chance to show off your roleplay skills. Baldur's Gate 3 does this famously.

I've done all three, depending on how much the player's powergame, how fun they find it, and how much I want to pretend to be a talking rat. There's no right answer, just what is right for your game. You can decide how intelligent animals are since you control their stat blocks, so you can vary their responses based off your whims.

There are three common approaches people take, and which one you take depends on your whims.

One common approach is to model them as very basic instinctual creatures. The birds will have a vague awareness of food and threats and such, but won't be able to communicate any complicated information due to their low intelligence scores. Complex requests won't be understood. This approach is good if you don't want to voice NPCs, want a more realistic approach, and want to avoid powergaming.

The second common approach is to model them as excitable toddlers. They have a decent amount of intelligence, can carry out a basic conversation, but can't understand complicated instructions and are pretty instinctual.

The third common approach is to model them as full NPCs, give them complicated histories and emotions, and use it as a chance to show off your roleplay skills. Baldur's Gate 3 does this famously.

I've done all three, depending on how much the player's powergame, how fun they find it, and how much I want to pretend to be a talking rat. There's no right answer, just what is right for your game. You can decide how intelligent animals are since you control their stat blocks, so you can vary their responses based off your whims.