If you want to create realistic scene in your level then package full of oneshot wave samples is there to to their job. Calm Sea Waves is 200+ individual sounds to randomize and scatter over the shore, just like there
Forest Birds sounds package
Spring has come for Unity3D game developers. Package full of individual phrases of various bird calls is available here. Unlike looped audio this package of oneshot sound samples you can achieve desired density of birds in your virtual forest. Get what you want and wherever you like with a little bit of C# scripting. If you like it dense, then you might to listen to this short stroll there…
no9 Footsteps Package
no9 Footsteps Package just landed in Unreal Marketplace. If you are Unreal Engine user then it might be worth checking. It is quite big and as name just states it contains various walking sounds:
https://www.unrealengine.com/marketplace/no9-footsteps-package