Thing is about Blackbird is that and I don’t know weather you have noticed but sometimes the blackbirds bill appears orange or on some blackbirds they can appear orange whereas on other they are yellow but yes a Blackbirds bill is usually yellow. But they have short bills whereas Starlings have longer bills. Another thing I should mention is with Starlings and Blackbirds young ones and females arnt yellow adult Starlings have yellow beaks just like Male Blackbirds do but the length of the bill is longer. I personally think I might of acidently painted a hybrid a mix of blackbird and Starling. The bird in the painting is looking away but you can see some of its tummy which is green and purple