Chronic INfertility of clutches

Question
I have a *beginner* pair that are now sitting on their 3rd clutch.  The first 2 clutches were INfertile, and I believe this 3rd clutch is also!  Based on 21 days from the time they actually starting sitting on the nest full time (BOTH stay on the nest, taking turns ONLY to come out to eat), the eggs are *due* to begin hatching on July 4th.  When I candled the eggs this morning, there are yolks present, but NO development, or even signs of fertility (no spider blood veins).

The female is 18 months old, the male is 3 years old.  Their diet consists of a variety of cooked & raw veggies, rice, pastas, eggs, millet, *some* regular seed, and have mineral block & cuttlebone in the cage at ALL times.

WHAT could be causing the INfertility of these clutches?  I am aware that sometimes there can be obstruction of the vent, which prevents *contact*, and considering these are new breeders, I considered that with the first 2 clutches.  Wouldn't the egg laying solve that problem for the hen?  Could it be the male?

I plan to let this pair sit out this clutch, then I plan to seperate them for a while to prevent anymore breeding, and *hopefully* stop the egg laying also!

Can you please give me some input on the INfertility issue!

Thank you!

Answer
Hi, Betty.  Thanks for posting.

Are you sure you have a true, bonded pair of birds, i.e., are you absolutely postive you have a male and female (females can lay infertile eggs without mating/being with a male)?  Do you have proof of their sexes (if this species of parrot is not sexually dimorphic)?  Sometimes they can fool people!  What species of parrots are these?  How are you sure of the hen's age...does she wear a leg band showing her year of hatching?      

Usually, when a female is successful at laying eggs, the problem lies with the male or the incubation process itself, provided you have a true male/female pair of birds.  The lack of "contact" you mention has to do with the amount of feathers around the vent (cloaca) opening...doesn't have to do with something being inside the body of the hen preventing the laying of eggs.  Very rarely would you have to trim the feathers around the vent in order to ensure fertility, but sometimes this is necessary.  There must be something else going on here.  Without additional details about the situation, I don't have a clue as to why this hen is laying infertile eggs.  Yes, it could be a problem with either the male or female, and it can be any number of things that could be wrong.  Type of diet has little to do with egg fertility.

I need more details in order to help you more.  Thanks.

Chrys