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.