After speaking to Jordan regarding my previous idea, I realised that it brought a lot of limitations to what I'd be able to do for a Secret Lair. After discussing it a bit more his advice was to focus completely on the avian aspect, with a dictator touch to it.
My first thought for the type of bird was a crow, and as Jordan said as well they do look very malicious which was perfect.
To add the "dictator" touch to it we also discussed what could be used. They wouldn't be able to have banners but the use of red leaves or torn cloth from humans would be more than acceptable to use.
The idea of the secret lair for the leader of the murder is either its nest or the inside of the a tree. Here I want to use the characteristics of the crow (which is hoarding shiny things) and relate it to what the Nazis did during WWII by hoarding art work, so the between avian and dictator will still be apparent.