They were diving in and out of the open top of the cone to feed their young and clean the nest out. A bit of multi-tasking you might say, certainly it must be relentless work feeding themselves, their young and doing the housework all at the same time. Apparently in two to three weeks the pair can catch up to 8,000 bugs and caterpillars; definitely a couple of farmers friends.
The books all say that they nest in holes in trees, walls, nest boxes and other hidden places so a redundant traffic cone must be a first and particularly at ground level.
What you might call thinking outside the nest box.
