Unusual behaviour continued

[Taz and Rio]

My little Rio has started sleeping on his first floor, up the back corner of his cage right next to his water drinker. His usual sleeping area is on the ground level, half covered by the level 1 platform with sawdust, bedding and a little blanket. Should I be concerned he is now sleeping in the open? Or could it just be the warm weather? I have posted previously regarding other changes in behaviour which is no longer a problem. He is well and eating/drinking as he would do normally. Today is the first time ive seen him sleeping in a different place and his cage hasnt been cleaned recently (within the last 6 days).

I would be greatful if anyone can suggest why he might be doing this. The only possible reason I can think off is the temp increase, but our house is much cooler than outside and the curtains and windows are always kept shut in his room, and the sun is never directly on the room he is in. Also, Rios brother Taz who lives in a seperate cage next to him hasnt changed his routine if thats of any relevance.

Thank you in advance!
Rio and Taz's mommy