Old owl box

Our owl box has stock pigeons and jackdaws in situ, no owls.
Over the last few days we have watched the jackdaws coming in with nesting materials. Ok that is normal this time of the year but at one time we watched 4 different ones all coming with nesting material into the same box, one after the other into the same box. What is going on?

 

It's probably a case of first come first served @On the Levels.