How does it work? I don't know how condors regulate their internal functions. As a human, I can control my muscles and my breathing, but I can't control, say, my digestion, my liver, my heart beat (except indirectly by either relaxing or doing stressful activities). How would a bird "flip the switch" and initiate asexual reproduction?
How can anyone answer a question about the subjective experience of a bird? :)
If I had to guess, it could be a subconscious switch happening based on environmental and mood factors, similiar to how human pregnancies can miscarry in times of extreme stress.
Lack of chemicals from the male to inhibit the process probably
Interestingly, in this case males were in fact available - it just seems based on genetic studies that they didn't participate in these particular chicks (the mothers went on to have other chicks through normal reproduction).
I don't know the answers to your questions, but parthenogenesis is confirmed to happen in other organisms. So I presume it could follow an analogous mechanism with condors.