Bluebird monitors each have there own area in which to monitor as many as 20 bluebird houses at leaset every two weeks and preferably on a weekly basis. To start out the nesting season (early March) The houses are cleared of any remnants of old nests or past occopancy. English sparrows are often desribed as the worst enemy od bluebords and their nests, eggs and young can legally destroyed. We do however allow tree swallows and wrens to use the boxes. Monitors carefully keep track of all eggs and newly hatched young, and register number fledged. after which, they remove nests and clean box for the next nesting.