Pekin Robin
Pekin Robin Leiothrix lutea.  

I have a pair of these, and the only way I can sex mine is by the cocks singing, visibly they are identical. They are very contented birds, and mix well, but have yet to breed. Alas they have not bred, even though they build a nest each year. I have had the cock since 1993, and I fear he does not have a lot of time left with us - he will be sorely missed.