Burrowing Snarrow

The Burrowing Snarrow is referred to only twice in the Pikmin series and is never seen in either. The first of these mentions is in the creature montage at the end of Pikmin 1:

The bluish hue of its feathers distinguishes it from the burrowing snarrow.

The second allusion to the creature is in Olimar's notes on the Burrowing Snagret in Pikmin 2's Piklopedia:

[...] Visually resembling the burrowing snagret is the burrowing snarrow, the range of which partially overlaps with the snagret's range. While the two may appear similar, when pulled from the ground they can be distinguished by the presence or absence of tail and wing markings.