Does this stance-poistion while sleeping mean that my budgie is cold?

sometimes when he is sitting on his favorite perch beside my bed, i notice he sits lower and has his little feet covered up with his feathers..as if he retracted them like landing gear on an airplane... or like one of those lowrider cars that have the hydraulics to lower down when they park to sit down on the pavement touching their frame.. is he sitting on his perch like that in an attempt to keep his feet warm?