Note that those two don't translate as "bird". An eagle is not "um pássaro". I think the right translation is "passerine".
In Cl Latin the word for a bird was avis and passer > Rom. 'pasăre' merely meant a sparrow or a "passerine bird" (sometimes also called "song birds") in a broader sense. Similarly, in Cl Latin the word for mice was mūs and only the shrew mice were called sorex > Rom. 'șoarece'... Does anyone know what is the fate of the original Latin words for a bird and a mouse in its daughter languages? Are they preserved in some form or were entirely wiped out?