Summary: A lake-effect hypothesis has been proposed to explain avian fatalities associated with utility-scale photovoltaic (USPV) facilities in the desert southwestern US.  The hypothesis suggests that passing birds perceive these facilities as water or some other oasis, alter course toward and attempt to occupy those facilities, and may succumb from impacts with structure or, in the case of some water-obligate birds, are behaviorally unable to take flight once landing.  This component of a broader project examines whether and how birds in fall respond while in flight to the presence of USPV facilities in southern California.  Data from portable radar show there was a disproportionate tendency for flying animals (birds and insects) to descend over facilities relative to control areas.  These descents occurred primarily among southbound animals during midday hours and may indicate response to a water-related cue such as polarized light reflection off solar panels or refuge-seeking behavior from animals facing intense daytime heat.  Attraction to USPV facilities does not necessarily indicate occupancy, however, and it remains unclear what proportion of animals that respond to the presence of these facilities actually expose themselves to hazards of attempted landing.