Owls (ne'ecdja') (H) are not differentiated very carefully in the literature, although they certainly are by the Navaho. According to Matthews, Eye Killers became poorwills (xo'cdodi'), which are said to sleep in the daytime and to come out at night to make things beautiful and the earth happy.
As Talking God left a council of Utes considering the fate of the hero of the Mountain Chant, Poorwill flew through the smokehole, circled around the tent four times, and flew out. Then the Utes began to nod and fell asleep.
Kicking Monster's children became various owls.
nike'ni, which YL identified as pygmy owl, is said to travel along the sides of the canyon.
nike'nl bitsili, pygmy owl's 'younger brother,' lives in brushy places.
na'ki' do'lyoci' (ceremonial name), 'nighthawk,' lives in gulleys.
tsidi' ldo hi, 'screechowi ' or 'elf owl,' is found in treetops. Matthews gives a pretty description of Screechowl (tsidi'ldohi):

Self Teacher met a short man who wore a skin-tight coat that was white on the chest and under the arms, and brown like the skin of a deer elsewhere. The bird does not fly off but sits and looks at a person, moving its head in every direction. It is associated with deer.
Another owl, associated with antelope, was called by the same name, but had a bluish face and skin like an antelope. YL identified the bird as screechowl.

Owls of one kind or another give information and ceremonial properties:

One came to the hero of the Night Chant and told him the formula for incense, which the gods fear.
One covered Rainboy with his (skin as a) blanket; another, on a different night, brought him a cottontail ready to eat, and covered him with his blanket.
An owl traded his medicine, aromatic sumac, with Monster Slayer for four kinds of tobacco. Owl also gave a wing feather for a prayerstick tamper.
Owl was a sorcerer who spirited a child away and taught it his lore. He is depicted as another manifestation of Deer Owner (Matthews 1887, p.397; 1897, pp. 123, 193, 244n; 1902, pp. 169, 205; Haile 1938b, p. 125; Reichard, Shooting Chant ms.; 1944d, p. 135; Newcomb 1940b, p. 69).

Navajo Religion, Vol II; Gladys A. Reichard, 1950

Owl: The Owl is a sacred, yet contradictory, bird in Native American mythology. In Kwakiutl myth, when this creature calls, it means someone is going to die. As messenger of death, the owl is not evil, but it can be foreboding. In the Pueblos along the Rio Grande in New Mexico, the owl is definitely a bird of dark omen. In the legendary moccasin game of the Navajo, the old stories tell of how Owl tried to hide the pebble under his wing to ensure that it would always be night. He was, however, caught cheating, and that is why night and day are divided equally. Pg. 198

The Gift of the Gila Monster, Navajo Ceremonial Tales; 1993, Gerald Hausman.