This is a Fanon name for the species of which Fecto Elfilis, Fecto Forgo, and Elfilin belong to, made by the author Cellidor including a entire fan interpretation lore dump of how the species exists, lives, and functions (Sexually or otherwise). A small excerpt reading is thus:

"'Starlings' (as they'll be referred to until Nintendo provides an actual species name) are cosmic entities, capable of inter-dimensional travel. Their name is derived from the shape of the wormholes they create in space to travel long distances instantaneously..."

The rest of which can be read in the description of post #3417062
Details on starling sexuality can be read in the description of post #3417213