Fertile eggs not soundsensitive

Heather Macleod, of Wanaka, asked:

I was given six presumably fertile eggs for my clucky hen but ended up with only one chick. The provider of the eggs was not surprised as there had been a loud thunderstorm the night I got them. The eggs were under the hen in her nesting box at the time. I am told that thunderstorms tend to kill the chick or embryo in the newly laid egg. Several other farmingtype folk have assured me this is true. Does the shape of the egg concentrate the sound, or are the little embryo chicks just very sensitive?

Neil Christensen, a veterinarian with Avivet Ltd who specialises in chickens, responded:

Fertilisation takes place in the fallopian tube soon after ovulation and well before the albumein and shell are laid down, so the egg would have been fertile or infertile when it was laid, well before the thunderstorm came along, and this state would not be altered.

Hatchability is a different issue than fertility. Ideally you would have broken out the unhatched eggs to determine (a) whether they were fertile or not (a fertile egg has a dot in the middle of the germinal disc, whereas an infertile one does not), and (b) what stage of incubation the embryo died if the egg was indeed fertile, and how this related to the occurrence of the thunderstorm(s).

Investigations into the effects of thunderstorms on hatchability are few and far between, and were mostly carried out 60plus years ago.

A Peter English noted in 1941, that thunderstorms had no effect on the hatchability of pheasant eggs.

Another investigator subjected prehatch incubating eggs to various abuses, including the detonation of sticks of dynamite close to the eggs. When the dynamite was buried near the eggs, unsurprisingly, there was considerable loss, but when the charge was detonated (a couple of feet) above the embryos, the treated eggs hatched as well as untreated ones. At 14 days, there was a greater loss than in untreated embryos (above ground charge), but from 1520 days there was no difference in hatchability (at this time the charges were in the ground).

In the graph, at 8, 9 and 14 days the detonation was above ground; on the other days it was below ground.

A colleague noted no effect of thunderstorms on hatchability in Indonesian birds. Millions of unincubated hatching eggs were shipped around the globe in the 1990s with minimal effect on hatchability.

I think we can be fairly sure that loud bangs do not significantly affect the hatchability of hens’ eggs.