A common theme in frequently asked questions concerns the viability of a fertilized loon egg. How cold can a loon egg get and still maintain viability? How hot? Does an unincubated egg remain in suspended animation and, if so, for how long? The truth is that we don’t have precise answers for these questions. And much of what we do know is based on other species of birds. When you are dealing with a state-threatened species, you can’t afford to experiment with the eggs. But based on what we think we know, let’s take a stab at some of the questions.
What goes on with the first laid egg during sporadic incubation before the second egg is laid? Since the egg isn’t being kept warm, we can assume that the embryo is not developing at the rate it normally would. But if we look at the evolution of eggs we see that more primitive eggs (amphibians and reptiles) are never actively incubated. Hatch time is governed by temperature. It seems logical that a freshly laid and unincubated loon egg could experience some development; just not as much as if it were being incubated. However, that would still give the first egg a developmental advantage over the second egg.
But what if the first egg isn’t incubated at all for 60 hours? Good question! I’ve been told that some fertilized bird eggs can be refrigerated for a week and remain viable. What we know for sure is that an unincubated loon egg will never hatch, but how long an egg can remain unincubated and still be viable is up for grabs. In the case of Loon Cam 1, the first egg got next to no incubation for the first 60 hours. If the nest hadn’t lost an egg and both eggs hatched, then we would know that the limit for viability is at least 60 hours. But, alas, an egg was lost so we won’t get the opportunity to increase our knowledge on this nest.
Can an egg get too hot? Yes. Eggs are protein-rich. Proteins are very susceptible to heat, which will cause them to change shape and no longer function properly. That’s why egg whites quickly solidify when fried. It’s estimated that, on a very hot day in full sun, the proteins in an exposed egg could be damaged in as little as a half hour. You’ll see overheated loons take a break from the nest during the hottest summer days, but you’ll rarely see them off the nest for more than 15 minutes.