Regularly occurring, usually migratory and typically nonbreeding species for which no significant or effective habitat conservation measures can be taken in Wisconsin. Species in this category are so widely and unreliably distributed during migration or in winter that no small set of sites could be set aside with the hope of significantly furthering their conservation. Typically, the SZ rank applies to a nonbreeding population. Reported from Wisconsin, but without persuasive documentation which would provide a basis for either accepting or rejecting the report. Possibly in peril in the state, but their status is uncertain.
More information is needed.
In other words, the conservation needs of these taxa may vary between seasons.