It turns out I have a nest of these birds in my garden. It is very well hidden, and only because I look for "patterns of movement", I found it. Mom and dad are working very hard to feed the younglings. They move extremely quick and make soft sounds communicating their presence to each other.
Using the shelter tent made it possible to sneak up close without disturbing them. Looking at the contents of their beaks, they really devour lots and lots of annoying bugs, flies etc...
Nikon D7000 + AF-D Nikkor 300mm F4 at 500ISO (only very slightly cropped)