May 30, 2021
Yes, real science! It may turn out to be real junk science, but it’s still science. After recording dates and times of Loon Cam nest events over the past four years and eight nest attempts, I’ve found some remarkably consistent timing between eggs being laid and eggs hatching, even though three different loon pairs were involved. By doing a few simple calculations we should be able to figure out some hatch times for these two eggs.
First we’ll start with time difference between egg#1 and egg#2 being laid. Most sources give a range of one to three days between eggs. Our sample size of reliable times (n=7) is in a tight range of 2.4 to 2.6 days, averaging 2.51 days. That’s remarkable for seven samples coming from three different pairs.
For total incubation time, we also have a pretty tight range if we separate 1st eggs from 2nd eggs. Incubation time for first eggs (n=6) has a range of 26.4 to 27.7 days (avg 27.2) . Second eggs (n=4) have a range of 25.4 to 26.7 days (avg 25.7). That’s kinda freaky; the range distributions are identical and exactly one day apart. Studies have shown that egg embryos can communicate with each other (https://newatlas.com/embryo-eggs-communicate-via-vibrations/60733/) and you might wonder if egg pairs are working out the schedule together. But that’s not the case. When we look at each pair (compare each egg to its nest mate) there is no correlation. The similar distributions are just serendipity. In statistical gobbledeespeak, we have skewed distributions; they don’t line up with each other.
So what’s causing the skew? There’s one factor that appears to be obvious: incubation effort between the first egg being laid and the second egg being laid. Typically, loons incubate the first egg only sporadically before the second egg is laid. It can be as little as just a few minutes a few times each day or it can be as much as maybe 50% of the time, maybe more. This is likely what causes the variation in the time between hatches, which ranged between 0.8 (assumed very little incubation before second egg) and 1.8 days (more incubation before second egg) (avg 1.4).
This year’s pair didn’t wait. From twelve hours after after the first egg was laid, the loons have been constantly on the nest. Egg#1 has gotten a good head start. Also, of all the nest attempts that hatched two eggs, this attempt has the longest time between eggs being laid (62.5 hours). I’m going to take the minimum first egg incubation time and subtract two hours: 26.3 days. For egg#2, the best I can do is take the average time: 25.7 days.
First egg hatch time: June 20, 1:22 PM
Second egg hatch time: June 22, 3:33 AM
I’m ready to eat humble pie.