Baby Birds Communicate Danger Before They are Hatched!

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.

Study overview

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.

When those eggs were reintroduced to the rest of their clutchmates (who were busy developing in relative silence),  they somehow transmitted the information — namely, that some kind of danger was near — to those who didn’t hear the warning calls!
unhatched bird study diagram
How the scientists figured out that unhatched birds had communicated with their nest mates
The transfer of knowledge about danger was evident in the way the clutchmates developed. Clutches that didn’t have any members exposed to warning calls developed differently than entire clutches that had a few members exposed to the calls.


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.”
It appears that clutches that were made aware of the danger developed to be more adequately prepared for it after birth.
Nature’s protective armor
The results of this study suggest that baby birds can hear, communicate and respond to danger while still developing in the egg.  It appears that nature has equipped these birds with a built-in “heads up” ability that actually aids in their survival.


Journal Reference: Noguera, J. & Velando, A. (2019). Bird embryos perceive vibratory cues of predation, Nature Ecology and Evolution Journal, Study / overview.

Study DOI:

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Raw data DOI: Figshare digital repository: