Zebra Finches Question?

Brief：
my pair of finches have been what appears to be nesting but im not sure if they are or if they are just playing with the string any help or suggestion.. 

my pair of finches have been what appears to be nesting but im not sure if they are or if they are just playing with the string any help or suggestions? also does anyone know how to tell how old they are. i hate getting animals from the pet store they dont know much.

After sexual adulthood even avian vets have a difficult time assessing the age of a bird. They become sexually mature at three months, so chances are that you do have an adult pair -- though they might be same sex, in which case there will be either no eggs or no fertile eggs. Birds will form same sex bonds when isolated from other sexes.

Zebras are dimorphic, so if both of your birds have the same markings, they're the same sex -- or one is a female and the other is a baby male. Even if they have different markings, one could still be an adult male and the other could be a baby male, in which case they're same sexes that look different but eventually will look the same.

Be careful what kind of string you offer them -- synthetic string can cause crop obstruction. Natural cotton from the small mammal section of a pet aisle is great replacement. Otherwise keep them warm and let them enjoy themselves. When there's nest activity, it usually is what it looks like. There's no way to assess age once Zebra finches get their full plumage in.

You can tell the male apart from the female via the 'cheek spots'. Males have a rust/orange colored spot on each cheek---females do not.

Do they have a nest box? If they don't they'll probably eventually lay eggs in the food dish or water dish (assuming you've a male and female). But they probably are exhibiting some nesting signs--most finches aren't interested in strings and such unless they're aiming to make a nest. they should have babies by now i gave my parakeets a nest they just used it as a playground