Which service class do methods retrieving lists of nested objects belong to?

This is applicable to any language, but I'm using Java for this so...

public class Egg {
    ...
}

public class BirdNest {

    private List<Egg> eggs;

    ...
}

I also have database entities which match these classes. Basically, BirdNest has 1:M relationship with Egg.

To perform persistance/retrieval actions on these classes I also have a BirdNestService and an EggService.

Say I want to retrieve a list of eggs from a given bird nest.

I could have a method like List<Egg> getEggs (int birdNestId);

My question is, which service should methods like this belong to?

It's performing operations based on a particular bird nest so you could argue it should be part of the BirdNestService.

Then again you could argue the item it is retrieving are Egg's so it should belong to the EggService.