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.