It is not unusual to see hawks perched on one foot, tucking the other foot in it's feathers to keep it warm.  It was not really cold, around 70 F, so this Harris's Hawk didn't tuck it's foot in but held it up.  When I first saw this it looked like a hand held across it's belly.  This species has  large feet:

• "They have powerful talons with curving claws and when they spot their prey and begin their feet-first diving descent to capture it, the talons lock onto the prey and tighten much like a zip tie. So a hawk�s feet are designed to catch their food. Struggle as they may, the seized prey very rarely can escape the powerful grasp of those talons." (from https://ginnybirdbeakspeak.com/2015/12/20/beaks-and-feet-harriss-hawk/)