A new study has revealed some rather surprising news: unhatched baby birds can sense danger and warn their nest mates of that danger before any of them are even hatched.
Researchers studied 90 yellow-legged gull eggs, divided into “clutches” (the term for all of the eggs in one nest). They separated some eggs in a clutch and played adult gull warning calls. As a result, the eggs started to move.
Embryos showed delayed hatching in the clutch group that had one unhatched bird exposed to gull alarm calls—that delay in hatching included the egg that was exposed to alarm calls and their unmanipulated clutch mates.
But the differences did not stop there
The effects of being exposed to the adult warning call prior to hatching–as well as nest mates who were tipped off by the unhatched bird who heard the initial warning call–lasted beyond the gestation phase. The communication by one unhatched bird to the unhatched nest mates changed the way the birds developed and affected their behavior after they hatched.
Chicks from the exposed clutches…
“were quicker to crouch after listening to adult alarm calls compared with chicks from the control group regardless of whether they were manipulated or not.”
Study DOI: https://doi.org/10.1038/s41559-019-0929-8
Location pdf: http://www.nature.com/natecolevol
Raw data DOI: Figshare digital repository: https://doi.org/10.6084/m9.figshare.651009