Learn English – Sparrow is to bird as snake, human, and lion is to __

It means exactly what it says: the hands of a sparrow.

This is a literary metaphor, so you have to figure it out for yourself. If somebody told you that so and so had hands like a sparrow’s, what would that be saying to you?

Whatever you come up with, that’s what it means.

Although your question is, as far as I can tell, new to ELU, it has been often asked before in other places, including this one. There it notes that the original from Gabriel García Márquez’s 1967 novel Cien años de soledad reads:

Primero llevaron el imán. Un gitano corpulento, de barba montaraz y manos de gorrión, que se presentó con el nombre de Melquiades, hizo una truculenta demostración pública de lo que él mismo llamaba la octava maravilla de los sabios alquimistas de Macedonia.

The highlighted expression manos de gorrión is Spanish for “the hands of a sparrow” — or for “a sparrow’s hands”, or for “sparrow hands”.

Again, there is nothing more for us to answer you here. It is a literary metaphor, and you must interpret it how you will.

As far as biology goes, something is amiss with this whole thing. Yes, unlike quadrupeds which have four feet, bipeds have two feet and two hands. But it isn’t really reasonable to talk about the hands of a man resembling those of a sparrow, for a sparrow’s hands are its wings not its feet. A bird’s feet hold claws, or talons if especially rapacious, but its hands hold feathers.

So already we know that we are in metaphor, not reality. If that were not sufficient, then referring to the eighth wonder of the alchemist wise men of Macedonia is a dead giveaway. Márquez is here echoing an earlier magical realist, famed Argentine writer Jorge Luis Borges — intentionally, I believe — who in El Aleph and Other Stories from 1949 wrote in his story “The Two Kings and the Two Labyrinths” about the “Isles of Babylon” (yet Babylon has no isles) and of the Seven Wonders of the World, where there was a labyrinth that was accounted the Eighth Wonder.

I would look then not to a sparrow’s feathery hands but rather to its taloned feet for understanding this metaphor. But beyond that we are in the realm of literary interpretation, which is outside of our charter here on ELU.

They are not interchangeable.

"He goes to church on Sundays" would imply frequent Sunday church attendance, but "He goes to church every Sunday" would mean (almost) invariable Sunday church attendance.

"He goes to church on Sundays" might also mean that Sundays is the day he goes to church, as opposed to Saturday, without implying anything about the frequency of attendance.

"He does not go to church on Sundays" means that he almost never goes to church on any Sunday, while "He does not go to church every Sunday" means that there are some Sundays he doesn't go to church.