From Birds of North America (BNA) account of northern saw-whet owls:
“Owl response rates lower on nights with wind speeds above Beaufort 2 than nights with wind speeds of Beaufort 0-2 (Stedman 2001)…Clark and Anderson (Clark and Anderson 1997) found that Saw-whet Owls were more vocal when cloud cover was between 50 and 75%…Owl populations may be more stable than auditory censuses suggest because more owls are known to be present than are calling in some years, based on pellet, roost, and roosting owl searches (Palmer 1987, Swengel and Swengel 1995)…Sing from within a half hour after sunset until sunrise. Calling peaks at 2 h after sunset and decreases until just before sunrise (Clark and Anderson 1997).”