First cuckoo or first cowbird?

We're all waiting anxiously to hear our first cuckoos, except maybe some of the smaller host species of passerine. Thinking about this parasitism reminded me of a scene that we witnessed back in Brazil. The species involved were not a cuckoo and a warbler or Dunnock, it was a Shiny Cowbird and Rufous -collared Sparrow.

Foster parent arrives with food and the cowbird chick starts to beg.

Feeding begins.

There isn't the difference in size that occurs between a cuckoo and its host
but the cowbird is still larger than its foster parent.

After the feeding period is over the cowbirds soon form up into small flocks of juveniles and you can't help wondering if they simply wake up one day and realise they are a cowbird or whether someone tells them! I mean, we think that birds have no sense of self, so how do they know they belong with the black birds and not the stripey brown ones that they have seen all their short lives. Fascinating stuff.