Parakeets mating

Question
My question is that we have 4 parakeets.  I know 1 was male and thought 3 were females.  1 male and 1 female were mating last year and she laid 11 eggs and all broke cause she laid them from the perch and fell on the bottom of cage last year so we just discarded them since they were all breaking.  Now, since last week the other 2 are also mating and thought they were both female cause there cere are exactly same, very dark.  I am sure they have to be opposite sex but the question is that I don't want any of them to mate cause I don't want to go thru egg binding or anything of such sort.  what can i do so they don't mate?  so, now all four are mating and i am afraid that they will lay eggs.  last year, when the other one laid and broke each one, she was getting very weakly looking and 1 egg looked like it was stuck and took a while to get out for her and i don't want them to go thru all that.  please help.  a friend of mine said that if you cover them for atleast 12 hours, they wont mate - is that true?  help.

Answer
The only way to guarantee that they won't mate is to separate males and females.  What your friend told you is partially true.  Budgies tend to breed during the spring and fall months, so if you keep the area around the cage darker for a longer period of time, they will think that winter is coming and will sometimes stop mating.  But you need to keep this up for several weeks for it to be effective.  Try that and you may also want to keep the room cooler for a little while too.  You don't want them to get too chilled or in a draft, but just keep it a few degrees cooler and make it darker and they will think that breeding season is over.