I think you can easily answer this question. The bright plumage of the male and the modest plumage of the female leave no room for reflection. We have repeatedly said that in pairs where both parents care about the offspring equally, it can be difficult to distinguish the male from the female. But when we see a clearly expressed difference, everything becomes clear at once. The brighter the plumage - the worst parent in front of you!
But you have to understand that I am only talking about situations where the plumage of the male and the female is different. For example, parrots have bright plumage, but at the same time, both parents have it, and not just one.
