Small and short variations in the temperature of incubating eggs can have significant developmental effects on the resulting hatchlings, research has shown.

In the matter of a species known as the bobwhite quail (Colinus virginianus), native to North America, a change of as little as one degree Celsius for just four days early in the incubation process produces baby quails that are – to use the technical term – clumsy as hell.

Researchers Starlie Belnap, John Currea and Robert Lickliter exposed several quail eggs to temperatures of 36.9 degrees Celsius, which is slightly cooler than the optimum incubation level, and 38.1 degrees, which is slightly warmer. A control cohort was kept at 37.5 degrees. {%recommended 6330%}

The temperatures were well within the range the eggs would encounter in the wild.

When the chicks hatched they were measured, and certain heat-related differences were apparent. Those from the cooler eggs had longer legs than the norm, and were slightly thinner – the predictable result, the researchers say, of the need to burn more energy when things are a bit colder than usual.

The ones from the warmer eggs had the opposite problem: they were a bit hefty, and comparatively stubby, little legs.

The real differences, however, became apparent with Belnap and colleagues played recordings of maternal adult quails, spurring the chicks to walk towards them.

In doing so, the chicks from the warmer and cooler eggs fell over three times more often than those from the control eggs. In addition, the stride length of the birds from the cooler eggs was noticeably uneven.

The conclusion is clear.

“We provide the first spatiotemporal evidence for the importance of optimal thermal microclimates for typical prenatal motor development,” the authors conclude.

The research is published in the journal Physiology & Behaviour.