Wee, poo and nest building

I bought this 'Disgusting digestion' kit, which is part of the Horrible science range, from a charity shop for £1.40. It has experiments to demonstrate the kidneys, stomach, bladder and bowels. The only thing missing is the fart pot!
We started with the bladder experiment.
First we had to make 500ml of wee, actually cold tea.
100ml at a time, the 'wee' was poured into the bladder. When we got to 400ml, the bladder started to leak.
and at 500ml, there was a big whoosh and the bladder emptied completely. The human bladder can hold 500ml of urine.

Next came the bowel experiment.
First oil is poured into the tube and then the plastic poo is squeezed along the tube.
This is tricky to do, and the girls wanted to pull the poo, but I made them stick to the squeezing, to demonstate the action of peristalsis.
Earthworms use a similar mechanism to move along.
The poo finally emerged at speed and bounced onto Rosanna's head!
Then on to do more experiments.
A robin has been very busy building a nest in the conifer. Nesting materials may be gathered up to a quarter of a mile from the nest area. We love watching the robin, if it comes back with something heavy for the nest, it rests of the bench, before taking the final journey to the nest.
I've read that the nest takes 2-6 days to build, but our Robin had been building for about 2 weeks. The nest may be started up to two weeks before the first eggs are laid.
Our friend told us about an experiment, you put out different coloured wools and see if the Robin has a favourite.
So we placed;
Fancy yarn
garden twine
green wool
pale blue wool.
The girls chose to place the wool in the trees and bushes. We placed out some hay for the Robin on a bench, but it completely ignored the hay.
Will our Robin have a favourite wool or will it stick to leaves, twigs and sticks?