Weak logic

This article at nature news states that cows align to magnetic fields. Wow, I can see the flaws in this before I even finished the first paragraph. Is magnetic force the only environmental clue to North - South? When they put a cow in an MRI and it turns toward the magnetic fields I will believe it, otherwise it is very weak and poorly thought out logic to develop such a conclusion.

To be fair, the article does say that it would have to be tested to have merit, so why start the argument with speculation? I can guess that even though bio-magnetism is real, this case is most likely due to the fact that it is easier to see and thus eat the grass in front of you if you don't shade the sun.