Eggs
Eggshell measurements were made on samples obtained from Operation Nest Egg (ONE), a program for the captive rearing of wild Apteryx eggs developed in 1994. Its purpose is to assist increasing wild population numbers by hatching wild-laid eggs in captivity and rearing the chicks until they gain enough weight to survive predation by introduced mammal species before release back into the wild (Colbourne et al. 2005). The eggs in this programme are generally collected after day 20 of incubation to increase the hatching success through artificial incubation. The eggs used in this study were retrieved after day 35 (range 35 to 60). After captive hatching eggshells were collected by staff members at Rainbow Springs, West Coast Wildlife Centre and Paparoa National Park and stored in sealable plastic bags with an identification code (collection locality and incubating male ID) and kept at room temperature until used in this study. The eggs are thoroughly cleaned upon arrival to the artificial incubation facilities.
Eggshells from 30 Brown Kiwi (A. mantelli ), four Roroa (A. haastii ), 25 Rowi (A. rowi ), and 20 Haast Tokoeka (A. australis australis ) from the 2013-2017 breeding seasons were used (n=79) (Table 1). The eggshells originated from seven different locations in the two islands of New Zealand (Co-ordinates in Table 1, Figure 1A). All of the eggshells used for thickness came from hatched eggs to ensure that the ratio of calcium intake from the mammillae during ontogenesis (Deeming 2002) was approximately the same between all the samples and did not interfere with thickness measurements; also, to ensure the climatic comparisons were accurate the eggshells used for this observation came from eggs that hatched during a single breeding season, 2015-2016, since these comprised the majority of the samples. The eggshells were relatively intact except for the section broken by the chick during hatching. Different comparisons (statistical tests) used different number of eggshells depending on the initial state of the eggshells and the purpose of the comparison. Rahn and Ar (1980) suggested that pore distribution varies according to the latitude of the egg; therefore, for the water vapour conductance comparisons of the three brown Apteryx species samples were taken manually from the equatorial region of each eggshell (Figure 1B) to ensure accurate comparisons. This area of the egg was chosen for two reasons; because of hatching, the blunt end of most egg samples was destroyed, this being the usual exit point for the chick. In addition, for some of the samples the eggshells were somewhat crushed, and the equatorial region was the only identifiable part of the eggshell. However, some of the eggs were intact enough to identify different eggshell regions, these eggshells were used for the repeated measures analysis were the water vapour conductance of the different species and eggshells regions were compared.
We begin by making a description of the different species eggshells using a variety of optical techniques.