Here's Barney coming in to land with some food with Fluffy already at the entrance hole.
He passes the food to Fluffy without demur ...
... who feeds it to the chicks.
Barney clearly feels some proprietorial feelings towards the chicks as although he has passed the food to Fluffy he follows up by entering the box so that he can see her feed the chicks.
This is not a once off behaviour pattern but a pattern that is repeated regularly and one that we have often noted in previous years.
You may just be able to make out the grub disappearing down the lucky chick's throat.
You can certainly see the frequent end result of feeding a chick - a faecal sac, here seen in Fluffy's beak.
Barney's baldness is also very clear in this image.
Click on the picture for a bigger version.