For the cowbird this is normal. Cowbirds are brood parasites, it’s snuck in whilst the robin was away and laid it’s egg for the robin to raise. If the robin is smart enough to notice what’s happened they will often still raise it anyway, as the adult cowbird will be keeping an eye on the host nest and will destroy the other eggs if the robin rejects it.
Yeah it shares a lot of stuff with Dishonored gameplay wise, but has a roguelike bent to it. It doesn’t compare in terms of world building but it’s still fun, especially for free.