Hi, i thought i would air my previuos experience with a housemartin many years back now. It fell out of the nest in our apex and was only very lightly feathered. Having an interest in nature i did my best for it with little knowledge. I fed it on small bits of bread soaked in milk and it survived and grew its feathers fine. i put it on the washing line and it would sway in the wind but never flew off. I was concerned it wouldnt know what to feed on when i realeased it as my dad told me i had too. So i fed it any small insect i could find in the last week or so, even small aphids etc. Eventually i released it in a field, threw him up in the air and he circled before flying off fast. I have no idea if he survived but at least i gave him a chance

. Good luck with your swallow dillemas. I would be inclined to try and get him back in the nest as thats his best chance but its hard to say how the others will react.