As we read on the Facebook profile of Nadleśnictwo Bolesławiec:

The wolves from Bury’s group have learned to “sing” in front of the cameras ;)

Nadleśnictwo Bolesławiec on the wolf concert

Why do wolves howl?

Foresters:

It turns out that the most important reason for howling is building bonds within the family group. It is a kind of mobile phone that helps announce where we will meet, call everyone together for a hunt, announce the end of the hunt, signal that it is time to start eating, and check where the young are.

Howling to other neighboring wolf groups is a warning that the territory is occupied and that we live here.

They also add:

And, of course, howling is also an element of play and learning. Just listen to young wolves as they learn to howl.