The dummy eggs I ordered from eBay arrived this morning: very quick delivery! BUT I am not impressed with the shape
Those of you who have used dummy eggs, can you please check these pictures and tell me if, in your opinion, Trilly will believe that they are her own?
The dummy eggs I have seen on cockatiel websites are more pointed on both ends; these I got are pointed on one side and much bigger on the other end.
I thought better check with you before doing the swap. I don't want her to feel like she has to re-lay 5 eggs

Another weird thing is that she only had ONE egg for ages, then laid the others faster than one every two days, I think she laid like two in three days. Can this be considered normal? She never laid in this time pattern before.

Anyway, here's the eggs

Those are definitely a weird shape but they might work. Cockatiel eggs naturally vary in size and shape, and the parent birds might not be too fussy. I don't know about cockatiels, but I've heard that budgies will accept a white marble, which looks a lot less like an egg than these do. Give them to her and see if she accepts them. If she does, all is good. If she doesn't, boil or freeze the real eggs and give them back to her so she doesn't start laying again.

I think she accepted them!
She has been inside the nest as usual so I think she didn't notice my theft of two of her eggs and the substitution.
How weird, they are so intelligent in many things... eggs is not one of them
She didn't even notice that there were one egg too many.

I think she had a moment of hesitation when she re-entered the cage and the nest: she sat on the top edge ogling the eggs, you know the way they do when they look at something intensely with only one eye... then she hopped in to never being seen again.

I candled the eggs and only had the heart to take away the clear ones, either they were not fertilised or they were just laid; the other three had veins so I put them back in the nest.

I boiled the ones I stole, for 3 minutes; one cracked so maybe 2 minutes would have been better. Now I have one boiled egg and I don't know what to do with it... I will show it to the boys tomorrow and see what they make of it, they have never seen one