The structure of Apteryx’s eggshell has generated much debate over the decades because it does not fit well with most allometric predictions. Apteryx eggshells are unusually thin and have been reported to be 60% less porous than expected. It has been suggested that these adaptations are compensations for a very long incubation period. Most studies so far have been carried out in what has been reported as Apteryx australis, and using infertile eggs or eggs laid in captivity. However, A. australis once comprised all kiwi with brown plumage, now separated into three distinct species: Brown Kiwi (A.mantelli), Rowi (A.rowi), and Tokoeka (A.australis). These three species use different habitats and live at different latitudes and altitudes. In addition, captive eggs are much smaller than wild laid eggs. These confounding factors make necessary to revise the assumptions made for Apteryx in the past. In this study, we analysed the physical characteristics of the Apteryx eggshells making a comparison between the three species of brown coloured kiwi and for some of the analysis we included some specimens of Roroa (A. haastii, Great Spotted Kiwi). We found that shell characteristics are different between the different species studied. The pore area of Apteryx eggshells was higher than previously suggested, and the water vapour conductance was much closer to what is expected for an egg that size. We found several new features such as triangular mineral particles composing the cuticle, only reported for a cretaceous Theropod, and the presence of plugs and caps on the eggshell pores. We suggest that the characteristics of the eggshells of the different species relate to the mating system of each species in addition to environmental variables, particularly pluviosity. We also suggest that the erosion of the cuticle during incubation is an adaptation to a long incubation period in a burrow.

Determining both individual age and population age distribution is crucial for an array of ecological studies. This is generating growing interest in molecular age markers such as telomere length. Most studies exploring the relationship between age and telomere length have been cross-sectional, but such studies face problems with large individual variation and the selective loss paradox. Thus, interest is growing rapidly for turning to longitudinal studies. In this study, the rate of telomere loss was analyzed for the extraordinarily long-lived North Island brown kiwi, Apteryx mantelli. Relative telomere length (RTL) was quantified using qPCR from blood from four separate sampling occasions across 14 years were analysed. Uniquely, the analysis of RTL was combined with high resolution analysis of genomic quality to get numerical values of DNA integrity. The analysis of RTL suggested a circa 5 % annual increase in A. mantelli telomere length. However, RTL was found to be highly correlative with DNA integrity, indicating that the perceived elongation of telomeres was a result of DNA quality differences between cohorts. Notably, the observed, positive correlation remained significant even when analyzing only samples classified as being of high DNA quality. Previous work has highlighted the potential impact of sample storage differences on RTL. However, to our knowledge, this is the first study to suggest that even small differences in DNA integrity between samples cohorts can impact the results of telomere studies. These findings are of great importance since longitudinal telomere studies of long-lived species tend to be “after the fact” utilizing already available samples for which handling and/or storage regimes might differ or be unknown. For such studies, we suggest that analysis of DNA quality with higher precision than traditional gel electrophoresis is needed to generate reliable results of telomere dynamics.