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Abstract Background Kiwi (Apteryx spp.) are flightless ratites from New Zealand whose numbers and distributions have declined following human arrival. Some of the kiwi species are known to hybridise but the extent of hybridization is unknown. Methods We reviewed hybridisation in kiwi (Apteryx spp.) and present new genetic data examining the extent of hybridisation between Rowi (A. rowi) and Little Spotted Kiwi (A. owenii) at Okarito, the location of the only remaining natural population of the threatened Rowi. We also genetically examined the syntype specimens of A. haastii Potts, 1872, collected from near Okarito in the 1870s, which have unusual morphologies. Results We found evidence of recurrent hybridisation between Rowi and Little Spotted Kiwi over the last 150 years, including one F1 hybrid found in the last 15 years, despite Little Spotted Kiwi’s likely extinction on the mainland in the 1970s. However, we found little evidence of introgression of Little Spotted Kiwi alleles into the extant Rowi population. The syntype specimens of A. haastii were also found to be hybrids between Little Spotted Kiwi and Rowi. Conclusions Our genetic analyses indicate that, although we detected multiple instances of hybridisation between Rowi and Little Spotted Kiwi, it does not appear to be an ongoing threat to Rowi. Because the syntype specimens of A. haastii are hybrids and therefore not representative of the prevailing usage of the name for the Great Spotted Kiwi (A. haastii), we resurrect the nomen oblitum A. maxima Sclater and Hochstetter, 1861 for the large spotted kiwi species.

Abstract Apteryx is a genus of flightless birds endemic to New Zealand known to lay very large eggs in proportion to body weight. The eggshell of Apteryx is unusually thin and less porous than allometrically expected possibly as a compensation for a very long incubation period. Past studies have been carried out on Apteryx australis, a species which once comprised all kiwi with brown plumage, now separated into three distinct species. These species use different habitats and live at different latitudes and altitudes, therefore generating a need to revise our knowledge of the attributes of their eggshells. In this study, we measured the physical characteristics and water conductance on eggshell fragments of these three species and Great‐spotted Kiwi and relate them to the environmental conditions of their respective environments; we also measured the water vapor conductance of Brown Kiwi eggs of late stages of incubation. We found that several trade‐offs exist between incubation behavior, environmental conditions, and eggshell structure. We found differences between species in eggshell water vapor conductance seemingly related to altitude; Brown Kiwi and Rowi generally inhabiting lower altitudes had the highest conductance and Tokoeka, generally living in montane environments, the lowest. This is achieved by an increased eggshell thickness rather than a pore area reduction. Finally, the water vapor conductance late in incubation was 58% higher than infertile unincubated eggs, suggesting a drastic increase in conductance throughout the long incubation period. Using the values previously reported, we calculated the embryonic eggshell thinning to be 32.5% at the equatorial region of the eggshell. We describe several new features, such as triangular mineral particles in the cuticle, reported for the extinct Trigonoolithus amoei, and confirmed the existence of plugged pores. We suggest that these structures provide microbial protection needed by a burrow nesting species with a long incubation period.

In 2013 there was an outbreak of crusting ventral dermatitis among a group of juvenile rowi (Apteryx rowi), a species of the endangered New Zealand kiwi, that were being raised on an off-shore island sanctuary. Biopsies taken at the time found nematodes migrating within the epidermis of affected skin but the specific identity and origin of the organisms was not established, and sporadic cases of similar skin disease continue to occur on the island. On examination of additional sections from the original skin biopsies, adult nematodes and eggs were identified, the histomorphology of which was consistent with Capillaria sensu lato. PCR was performed on DNA extracted from archived formalin-fixed, paraffin-embedded tissue blocks of skin from eight affected rowi, using primers targeting the 18S region of nuclear ribosomal DNA and the COI gene of mitochondrial DNA of capillarid nematodes. The 18S sequences from all rowi samples were identical and matched sequences from members of the genus Eucoleus. In contrast, two distinct capillarid COI sequences were obtained, in one case both from the same rowi skin biopsy. While there were no close matches, both COI sequences also aligned nearest to sequences identified as Eucoleus spp. It is considered unlikely that two different nematode species are involved in the rowi skin lesions and the possible amplification of a COI pseudogene or “numt” is discussed. A species-level identification of the capillarid nematodes causing skin disease in rowi was not obtained, however based on histological evaluation the infections include reproductively-active adult nematodes. This finding indicates the possibility of perpetuation of the skin disease in the absence of the original source, as well as raising potential for the transfer of infection from the island when the juvenile rowi are translocated to their new habitats.