Family Of Geese Adopt Adorable Duckling
Geese are much better parents than ducks from as you can see. Notice both parents here protecting their goslings, making sure that not one is left behind. Don't really see that with ducks. And at the duck pond near my childhood home, there always were some ducks with a slew of ducklings of at least 2 different ages -- seem some mother ducks were happy to get rid of their ducklings as soon as another mother duck came swimming by. It’s actually just a younger gosling, not a ducking. Geese are excellent at adopting young from other nests and will sometimes co-parent for better protection. Geese may be assholes, but they are wonderful parents.
That seems reductive. What if you had a group that was inclined to help each other out and a group that wasn’t (or simply individuals) all competing for the same resources? In that case, the ones acting in mutual interest are likely to survive. That’s basically how the current specification in orcas started. Something of a unique case since resident orcas typically won’t mate with transient orcas, even when they’re in proximity, which is pretty unique. But what you’re describing certainly isn’t universal. Especially if we look at situations in which you have a community of one species working against individuals of another.
You’re also kind of viewing evolution as sort of selecting specific results without really considering that genes typically come as a package deal with good and bad. Evolution can select for things that are, arguably, bad in and of themselves simply because it’s packaged with beneficial traits. Or a trait that seems negative in one context could be propagated because some other effect of that trait is or was positive. For example, a gene that makes a goose extra protective of chicks likely benefits their own chicks significantly. If that same gene compels them to pick up a few stragglers, it’s still very possible that gene still confers an advantage over a goose that doesn’t have that gene, even accounting for the fact they’re raising one of the other goose’s young.
It is naturally possible for any kind of duck to cross with any other breed of duck, and any goose kind can also cross with other breeds of geese. Sometimes a goose will try to mate with a duck, or vice-versa, but even if they mate effectively, the resulting eggs would not be fertile.