Table 1.

Nomenclature and description of parameters and response variables

Parameters and Variables	Acronym	Definition	Description
Eggshell ultrastructure parameters	Shell	Mineralized eggshell	Total eggshell thickness (μm)
	PL	Palisade Layer	Outermost layer thickness of the eggshell or effective thickness (μm)
	ML	Mammillary Layer	Innermost layer thickness of the eggshell (μm)
	MCs	Mammillary Cones	Number of mammillary cones
Grain size and shape indexes	$\overline{A}$	Mean grain area	Mean value from all individual grain Ai measurements per shell sample (μm2)
	CED	Circle Equivalent Diameter	Diameter of a circle with area value $\overline{A}$ (μm) (Equation 1)
	Ei	grain Ellipticity	1-x/y; where (x,y) are short and long axes of the fitted ellipse for each grain Ai constituting a shell sample (dimensionless variable) (Equation 2)
Grain boundary (GB) parameters	LAB density	Low-Angle Boundary density	Low-energy intra-crystalline boundaries (3° < ω < 15°) per unit of scanned area (μm−1)
	HAB density	High-Angle Boundary density	High-energy inter-crystalline boundaries (15° < ω < 110°) per unit of scanned area (μm−1)
	TAB density	Total-Angle Boundary density	Low- and high-energy intra- and inter-crystalline boundaries (3° < ω < 110°) per unit of scanned area (μm−1)
Ultrastructure variables	Rel. Shellvol	Relative shell thickness	Residual values of the egg volume (independent variable) on shell thickness (response variable) regression line
	Rel. PLvol	Relative PL thickness	Residual values of the egg volume (independent variable) on PL thickness (response variable) regression line
	Rel. MLvol	Relative ML thickness	Residual values of the egg volume (independent variable) on ML thickness (response variable) regression line
	Rel. PLshell	Relative PL thickness	Residual values of the shell thickness (independent variable) on PL thickness (response variable) regression line
	Rel. MLshell	Relative ML thickness	Residual values of the shell thickness (as independent variable) on ML thickness (response variable) regression line
	PL ratio	Proportional thickness of the PL	100(PL thickness/shell thickness), dimensionless variable
	MC density	Mammillary Cone density	Number of MC per mm of cross-sectional eggshell profile (#MC/mm) (Figure S6)
	Rel. MC	Relative MC	Multiplication of the MC density by the eggshell perimeter (dimensionless variable)
Microstructure variables	Rel. CED	Relative CED	Division of the CED by the PL thickness (dimensionless variable independent of the scanned area and egg size)
	$\overline{E}$	Mean grain Ellipticity	Mean value from all individual grain ellipticity (Ei) measurements per shell sample (dimensionless variable)
	Rel. $\overline{E}$PL	Relative Ellipticity	Residual values of the PL thickness (as independent variable) on $\overline{E}$ (response variable) regression line
	Rel. LAB	Relative LAB	Multiplication of LAB density by the PL thickness (dimensionless variable independent of the scanned area and egg size)
	Rel. HAB	Relative HAB	Multiplication of HAB density by the PL thickness (dimensionless variable independent of the scanned area and egg size)
	Rel. TAB	Relative TAB	Multiplication of TAB density by the PL thickness (dimensionless variable independent of the scanned area and egg size)
Textural severity variables	Kμ	Average of all KAM values per shell sample	Each KAM value is calculated as average misorientation between a point and its designated number of neighboring points (Figure 1)
	Km	Median of all KAM values per shell sample	Each KAM value is calculated as average misorientation between a point and its designated number of neighboring points (Figure 1)
	pfJ	J-index (pfJ-index)	pfJ-index quantifies the sharpness of a pole figure (Equation 3)
	Mp	M-index	Mp quantifies the crystallographic preferred orientation (CPO) strength, and it was calculated for all points analyzed by EBSD to evaluate the dependence of fabric strength on the intracrystalline microstructure (Equation 4)
	Mg	M-index	Mg quantifies the CPO strength, and it was calculated for one point per grain by mean orientation of each grain to exclude the influence of intracrystalline microstructures on the strength of the eggshell (Equation 4)
	fT	Transverse direction Kearns texture factor	fT is defined as a weighted average of the basal pole figure intensity with respect to the sample normal direction (Equation 5)