Crap! I was afraid this might happen. My guess is that they are 'thinking about' the next clutch and have stopped brooding the squab. Some cocks will take over for the hen (my Birmingham Rollers were super dads) but others will not. I am concerned for Bugsy if you can not provide some heat source. Also keep an eye on him to see that they continue feeding him and his crop is full. Aren't there reptile heating pads that could be put under the nest bowl. or a hot water bottle, Or what about one of those hand/boot warmer packets? Bringing him inside would work for sure, but might also cause them to further abandon their parenting.