Awesome photo on the house wren nest Gulo! Thank you! I love wrens, I only get to see the splendor of the house wren in winter time down here.
I don't know what it is about the brains of rats, but many raptors down here seem to just eat the heads off rodents and let the micro-carnivores have the rest. I guess the brain is high in fat and energy or something I've also seen many mammals eat on the head, and leave the rest.
Lots of barn owls down here and often when you peek in on their nest there is a lot of dead rodents with only their heads eaten off. The Harris hawks down here often run in little posses together. I think they may be more intelligent than other raptors for that reason. Often, when I'm shredding or cutting hay on a big pasture, raptors will swing by and follow the tractor catching bugs and Sigmodons and such. I think the Harris hawks may be doing the same thing with the indigos as I found woodrats with their heads eaten off by the birds while the snake is working.
Indigos down here are homewreckers. They go into a mitten and everything comes out. You can listen for them too; as many of the little birds will tattle-tale on them. They have really good eyesight too! When I see one, I approach it slowly like a trapped skunk. Often, when I get about 20' away, they will raise there head up off the ground a good ways and look right at you, much like a coachwhip does. It can be quite intimidating on the really big ones. Usually, if I just hold back, they will start doing their thing again and working mittens and will let me follow along if the brush aint too thick. I often wonder if they are looking for rattlesnakes in the mittens; as I have never watched one eat a rat. I'm sure they do though. I think they are a lot like alligators too as far as being curious and attracted to thrashing noises. I've chased a lot of downed birds hunting quail and dove and one time I had a wounded scaled quail go down that was fluttering around in the brush. When I went to retrieve it, an indigo had beat me to him. Sure wish I had pics of that.