Phoebe young still being fed!

After losing track of the phoebe family for several days and thinking the young were independent with each one moving on, I was surprised to find a parent with 2 young phoebes yesterday right next to the location where they nested. And I was more surprised to see the parent feeding each of the young birds--these young phoebes were now 15 days from fledging! This surprised me as the Black Phoebes (at least both parents appeared to be Black Phoebes and not in intermediate plumage as one of these parents) that I have followed in the past have caught their own food much earlier than this. However, since these are apparent hybrid BlackXEastern Phoebes, I checked Birds of North America online and found that the little documentation they have on Eastern Phoebes indicates they may be fed by parents up to 14-17 days post fledging. This source had little info on young Black Phoebes but there is evidence that young of this species will start making 'foraging flights' during the first 3 days post fledging. Interesting. More later. SeEtta