Statistical analysis
A discriminant analysis was used to determine the degree of association of each eggshell sample with the donor species to determine the degree of differentiation between the four species of Apteryx . This was done to determine if the eggshells of Brown kiwi, Rowi, Roroa, and Haast Tokoeka were different and could be associated with environmental variables. For this, we used weather information from the area the egg was collected; the average monthly temperature, pluviosity, and barometric pressure from April 2015 to February 2016 was obtained from worldweatheronline.com. A spearman rank correlation was performed for eggshell thickness, pore density, and pore radius with each of the mentioned climatic variables.
A one-way ANOVA was performed using the samples from Brown kiwi, Rowi and Haast Tokoeka to determine if there was a significant difference in terms of eggshell thickness and cuticular thickness; Roroa was not included in this or any further analysis, as the sample size of eggs was too small.
An ANOVA was used to test if there were differences in water vapour conductance between the species and a nested linear model was used to test the different eggshell regions. In this case the fragments (E, A and B) were nested within species. All the ANOVA’s performed in this study were followed by a Tukey post hoc test to assert which species differ from each other. A repeated measures ANOVA was used to determine the difference in water vapour conductance of three different regions of the eggshell of Brown kiwi, Rowi and Haast Tokoeka, and to determine the extent of the interaction of the species and the region of the eggshell.
A paired T-test was performed to compare the water vapour conductance of whole Brown Kiwi eggs being incubated by ONE and the water vapour conductance calculated from Eq. 6. using the mass of the egg. All the statistical analysis in this study were made using MiniTab™ 18 Statistical Software.