I am lucky enough to have 2 of my nesting boxes being put to good use this year. One is being used by House Wrens which are constantly bringing food in to their young.
The House Wrens occassionally fly directly into the nestbox with the food and other times they perch on nearby branches before entering. Sometimes they hang on the edge of the box - especially if the other adult is in the box waiting for them to exit. Space is limited!!
Another box, that is smothered in Clematis has been home for a family of Chickadees. They have no problem negotiating their way into the box with a continuous supply of food for their young.
all photos © Jane Binns