“Rare” is context-dependent. My Collins Bird Guide lists the Dark-eyed Junco as a “rare vagrant,” but that is, of course, because Collins is a bird guide to Europe. Common birds where you don’t expect to find them are exciting. We have our own rarities at the banding station, birds that may be common in the general region but rarely grace our nets; and although no one else would consider them remotely remarkable, we still get excited.
Juncos flock in huge numbers all around the area, but for whatever reason, they do not like the specific patch of riparian land that the banding station monitors. The banding station catches only around five juncos every year, making them rare by our very particular standards.