Egg spots correlate with stress levels in birds
Counting the spots on the eggs of hens can be an answer in measuring the health of the birds. Apparently, the spottier the egg, the more stressed the parent.
The team studied 112 blue tit (Cyanistes caeruleus) egg clutches in central Spain. The parents were weighed and blood was taken for testing. They discovered that eggs with more spots represented a mother that weighed less and had higher cellular concentrations of a stress-related protein (HSP70). (Journal of Avian Biology).
The team, Santiago Merino and colleagues at the University of AlcalÃ¡, Spain, suggests that the eggshell pigment protoporphyrin is responsible for the correlation. As stress levels increase, so do the pigment chemical, this would explain the greater coloration in the eggshell when it is laid.