Yesterday (March 19th) the Norfolk eagles apparently laid a second egg. Apparently is the operative word. This is based solely on the posture and behavior of the female. We've been fooled before - we had assumed the first clutch contained three eggs, not until the eggs were retrieved did we learn we'd been fooled.
The eggs haven't been incubated much today - sparking much concern over the egg's viability. At this early stage continual incubation isn't necessary. If another egg is forthcoming, this may actually ensure that all of the eggs hatch closer together by slowing development of the embryos. The eggs are able to withstand some cooling...how much hasn't been quantified. Temps today are around 56 F in Norfolk, and the sun has been shining on the nest. We have to assume that these eagles know their business and not leap to unfortunate conclusions.