2004 This is my most interesting nest of the season. This nest started out as a Tree Swallow, with another Tree Swallow nesting 10' apart. Then, three Bluebird eggs appear in the same nest with another Bluebird nest on top of the other Tree Swallow nest 10' apart... are you following? Yes, confusing I know. =) It seems the Bluebird are trying to claim one of the paired boxes when 2 Tree Swallow pairs have already laid claim to both. No one seems willing to give up their nest. One will win out eventually with eggs lost in the process. This is the Bluebird pars second brood of the season.