Hand rearing lovebirds

Question
Hi there,

I have two little lovebirds.  Their parents were removed from the nests and they were discovered only later.  Naturally they now have to be hand reared.

They survived the critical stages, and one is about a week older than the other I suspect.  They come from two different nests.  
I feed them with a syringe about every 3 hours at the moment. I think the oldest one is about 5 weeks and it has some little wing and tailfeathers already.  The baby I think is 3 weeks, he has only down and the feathers are starting to show black tips on his wings.

The little one is always hungry and a very greedy eater.  The older one can already perch on my finger or on a little seating stick.
They love attention and are very eager to be picked up or held.

1. Is there any way I can determine their age?
2. How do I know when I can start weaning them or does it not matter?
3. How do I make sure that I do not over/under feed them? My last feed is at about 9am, and the first at about 06:30am, is that ok?
4. How long should I keep them in a nest format before introducing them to a cage?
It's winter now so quite cold, but I think they might get bored in the dark box and would like for them to interact with the momevent around them.
5. The little one always tries to feed from the bigger one's beak like it would do with a parent.  I am scared injuries might occur this way although up to now none has.

Eagerly awaiting your expert advise.

Answer
Hi, Janie.  Thanks for posting.

1.  Sounds to me like you already have a good estimate on their ages.  You won't know for sure how old they are unless someone actually wrote down the date they hatched and can give you this information.  However, you can guesstimate as best as possible:  eyes open up at about 10 days, pin feathers start emerging about 2-3 weeks, they should start pecking at items on bottom of cage at about 3-4 weeks of age, etc.  
2.  I start weaning baby lovebirds at 4 weeks of age, if the baby is ready.  Lovebirds need to imprint on humans at as early age as possible so they will be tame pet birds.  When they start pecking at stuff on their brooder/cage bottom, you can start the weaning process (I start it at 4 weeks regardless).
3.  I handfeed lovebirds under 4 weeks of age every 4-5 hours or whenever their crops become empty (varies with each bird).  Your times are good it seems.  The rule of thumb is whenever the crop is empty, except during the nighttime hours.  It doesn't hurt them to be a little bit hungry if you can't meet a regular time (if you happen to be out shopping or something), but don't go too far over the time.
4.  If they don't have their parents to care for them, you should have them in some type of brooder situation where they have sufficient warmth, humidity, etc.  They shouldn't still be in a nest without their parents....they need heat in order to process their food.  They can be introduced to a cage when they can walk and climb on the cage wire and have enough feathers to keep them warm enough.  Otherwise, the 3-week old should be in a brooder type setup and the 5-week old could probably be in a cage, but I think I might leave the 5-week old with the 3-week old so they have warmth and companionship.  They need to be able to see their surroundings and the world around them.  
5.  Babies often try to feed off their clutchmates...this is normal.  Their beaks are still soft so I doubt injuries would occur.  How much formula are you feeding each per feeding (are you feeding enough at each feeding)?

Chrys