They are chimney swifts. The parent birds make nests out of twigs and use spit to adhere them to the walls of the chimney. Often as the birds get older and heavier, the "glue" lets go and down comes the nest and babies. It looks like they are still sitting on what is left of the nest. Keep an eye on them because the parents might not go down there to feed them. You may have to call a local wildlife rehabber.
You should be able to hear them chatter every 15-20 minutes if the parents are feeding them. You could watch if you are patient and remain still. If half an hour goes by and there is no sign of the parents, they probably are not getting fed. Unfortunately, if the chicks begin to huddle and act listless, it may be too late to save them. Some people might disagree with me but calling a local wildlife rehabber may be the best option. If there is NO sign of the parents you could try feeding them yourself. I have rehabbed a few of these for the very reason that their nests fall and end up in people's fireplaces. The parents who build these flimsy nests are usually young and inexperienced and will abandon their chicks and start over with a sturdier nest. The chicks are not difficult to feed. Soaked dry puppy food and a heating pad is all you need
The chimney is obviously open so I hope the parent will fly down. We had it closed off until we had the money to get the whole thing cleaned and repaired, plus a top put on.
Do the parents rest with the chicks at night? Or somewhere else?
How old do you think these are?
If I have to start feeding them and can't I get in contact with a rehab center, how often do I have to feed them? Not sure I have a heating pad any more.
I don't have cheap puppy food in my house. My 3.5 week old pups are just starting to get an ALS dog food with milk replacer and cottage cheese. The food has 470cal which is about 100 more calories than the cheap stuff most people have in their homes.
I have them every year. Even left the chimney top open for them after I figured out how many (amazing!) mosquito's they eat on a daily basis. I have a 'welcome chimney swifts' sign out since. The flying sounds take some getting used to. It sounds like they just bat their wings and cannot fly, when in fact, they do just great, -adults do the same- but seem to have this strange (sound) pattern. I do keep my damper closed because I do not want them in the house. I enjoy the groups company from spring to late fall when they take off again. Mine are more active in the evenings, but I have never had to interfere. The only one that I had ever lost was when the damper was still open (and one baby got into the house when I was gone for a few days)
Good luck with them. I hope it works out. They are great little swallows to have around.
How are they doing today? I would say they are about a week old. The parents will sit on them for the first few days and then will perch nearby. They would have to be fed about once every 20 minutes to half an hour. Not as often as they get older. Most any dried dog food would work. It is not an exact science. Timing is more critical.