Striped patterns on boids are occasionally caused by spikes in the incubation temp, but that is very rare. Striped patterns are much more commonly caused by incubation temps that are slightly below optimal. Incubation of Angolan eggs in the sub-optimal mid-80's or short term temp drops into the low 80's during incubation would elicit a high degree of probability in producing some amount of striped patterns within a given clutch.

Kelly