with chickens... do they wait for a full clutch to start brooding....

Some hens never go broody. But they do not sit on them after theye first egg. I have some that are always broody, and then my sebright never has! I ususlly collect the eggs and when one goes broody (if she is on the nest all day) I will place the eggs under at night. This way they don't get rolled around and get broken or scrambled.

 

Chicken eggs take 21 days to hatch. This can vary by several hours so you may see a chick hatching early on the 20th day and others hatching almost at the 22nd day, but 21 is the "standard". This means whether you use an incubator or a broody hen to hatch eggs, they should all get started at the same time. Otherwise you will have problems.

This means it is best to collect the eggs every day. From the tone of your post, I'm not sure you are doing that. There are many other reasons to collect the eggs every day. Some people collect 2 or 3 times a day. I personally think once a day, in the evening, is sufficient. Personal choice. Leaving eggs in the nest overnight is a temptation to predators. Eggs are less likely to get broken if they are not in the nest. Eggs left in the nest can encourage egg-eating, a horrible fate. Eggs will stay fresher in your house. I'm sure I'm missing several reasons, but I cannot think of one reason to leave the hen's eggs in the nest.

It is usually a good idea to leave one or more fake eggs in the nest. This can be golf balls, plastic or wooden eggs, even egg-shaped rocks. This shows the hens where to lay.

Many people on here will tell you it is absolutely necessary to isolate a broody hen from the flock while she is on the nest. Others don't do that. I'll not get into the why's here. Plenty of threads about that. If you do decide to leave the hen with the flock, you need to mark all the eggs you want her to hatch so they can be clearly identified. You can use a black magic marker, black ink or a soft-leaded pencil. As an aside, if you use a soft-leaded pencil, make wide bands as thin lines tend to disappear. Put all the marked eggs in her nest at the same time. Then you will need to check under her every day and remove any freshly laid (unmarked) eggs. As long as you remove them daily, they are still good to eat.

A hen will go broody only when her hormones tell her to. Some breeds tend to go broody a lot more than others. Mark Rosen inthe April/May edition of Backyard Poultry suggests you can encourage a hen to go broody by leaving several eggs in the nest and putting the hen on a low-protein (grain) diet. (He does not say it, but those eggs can be the fake eggs.) Others (Gritsar, are you listening) will tell you this does not always work. Broody hens do not lay eggs. As Helen Ussery suggests in the June/July 2006 edition of Backyard Poultry, since egg producers made going broody a capital offense, they have almost bred broodiness out of several production breeds.

I've probably given you a lot more than you were asking and forgive me if I sound preachy. Hope this helps some.