T A N E 30,1984

S U R V E Y O F H E N (TARANGA) I S L A N D I N V E R T E B R A T E S A S P O T E N T I A L FOOD F O R T H E L I T T L E S P O T T E D K I W I ,

APTERYX OWENI

by Abdul Moeed and M . J . Meads Ecology Division, DSIR, Private Bag, Lower Hutt

S U M M A R Y

The forest invertebrate fauna on Hen (Taranga) Island was compared with that from Kapiti Island. Invertebrates eaten by the little spotted kiwi (Apteryx oweni) on Kapiti Island were also found on Hen Island, suggesting that the invertebrate food resources could support some kiwis on Hen Island.

INTRODUCTION

We visited Hen (Taranga) Island between 12 and 16 March 1984 to investigate the invertebrate fauna and the island's potential as a future habitat for the little spotted kiwi (Apteryx oweni), which is probably now restricted in distribution to Kapiti Island.

Hen Island (35° 58'S, 174° 43'E) is 16 km off the North Island coast (Fig. la). It covers 476 ha, with the highest point at 427 m A .S .L . The forest is of a northern rain-forest type whose structure and composition has been described by Cranwell and Moore (1935). The structure of the topsoil has been described by Cochrane (1954). The island lies in a climatic zone which experiences very warm and humid summers and mild winters (Robertson 1959).

The survey was carried out by us as on Kapiti Island (Moeed and Meads, in press a).

T H E S T U D Y SITES

The study sites were located on the north-western and southern parts of the island (Fig. lb). Site A was in Stead Bay and site B in Wahine Bay. The vegetation of site A consisted of kanuka (Leptospermum ericoides), pohutukawa (Metrosideros excelsa), kohuhu (Pittosporum tenuifolium), Carmichaelia williamsii, hangehange (Geniostoma ligustrifolium), Coprosma grandifolia, kohekohe (Dysoxylum spectabile), kawakawa (Macropiper excelsum), whau (Entelia arborescens), karaka (Corynocarpus laevigatus), and ferns (Asplenium lamprophyllum and A. oblongifolium). Vegetation at site B included puriri (Vitex lucens), taraire (Beilschmiedia tarairi), pohutukawa, karaka, kohekohe, nikau palm (Rhopalostylis sapida), kawakawa, mahoe (Melicytus ramiflorus), puka (Meryta sinclairii), and ferns (A.

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lamprophylum and A . oblongifolium). The leaf Utter and decaying vegetation was 50-70 mm deep at both

study sites. The topsoil of site A comprised silty clay loams while at site

0 1 km

I

Fig. 1. The location (a) and the study sites (b) on Hen Island.

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B it was of friable loams laced with matted roots. Both sites were representative of the surrounding area.

M E T H O D S

Invertebrates were collected by hand by day and night, and 10 pitfall traps (Moeed and Meads, in press b) were left set for a month to collect surface-dwelling invertebrates. Gait's solution (see Barber 1930) was used as preservative. Forest Utter was collected from five 200 x 200 mm quadrats, to a depth of approximately 75 mm. Litter samples were brought to the laboratory in cloth bags and put through Tullgren extractors to collect Utter-inhabiting invertebrates. Five 200 x 200 mm quadrats of soil, approximately 200 mm deep, were examined on site for visible invertebrates.

The data were analysed using a chi-squared test for differences between catches from different sites on Hen Island and from Kapiti Island. The significance is expressed by the P values in brackets.

R E S U L T S

Pitfall traps The majority of invertebrate groups, as revealed by pitfall traps, were

roughly the same on Hen Island as on Kapiti Island (Table 1). Overall, more invertebrates were trapped on Kapiti followed by site B and site A on Hen (P less than 0.001). The difference between the two sites on Hen Island in the number of individuals caught in the various invertebrate groups was significant only for beetles (Coleoptera) and isopods (Isopoda). More beetles were trapped at site B (P less than 0.001) and more isopods at site A (P less than 0.001). The difference between the number of beetles caught at the two sites on Hen Island and on Kapiti was significant (P less than 0.001), with greater numbers trapped in site B on Hen Island, followed by Kapiti and site A on Hen. More isopods were trapped on Hen Island than on Kapiti (P less than 0.001).

Significantly more flies (Diptera) (P less than 0.001), ants (Hymenoptera) (P less than 0.025), larval insects (Coleoptera, Diptera, Lepidoptera) (P less than 0.001), spiders (Araneida) (P less than 0.001), and amphipods (Amphipoda) (P less than 0.001) were trapped on Kapiti than on Hen Island. In addition, although more wetas (Orthoptera), thrips (Thysanoptera), wasps (Hymenoptera), centipedes (Chilopoda), and earthworms (Terricolae) were trapped on Kapiti and more native bristle-tails (Archaeognatha), cockroaches (Blattodea), weevils (Coleoptera), pseudoscorpions (Pseudoscorpionidea), harvestmen (Opiliones), millipedes (Diplopoda), and snails (Pulmonata) were trapped on Hen Island, the numbers were too small to statistically test the differences.

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Table 1. Number of invertebrates collected in pitfall traps and extracted from 0.2 m 1 of forest litter from site A and B on Hen Island. Figures for Kapiti Island (Moeed and Meads, in press a) are for comparison (*, not counted).

Pitfall traps Litter Invertebrates Hen Island Kapiti Island Hen Island Kapiti Island

A B (Te Rere) A B (Te Rere) Archaeognatha 2 1 0 0 0 0 Collembola * * * 487 289 2216 Blattodea 2 0 0 1 1 0 Orthoptera 5 1 11 0 0 0 Psocoptera 0 0 1 0 4 3 Hemiptera 15 1 15 36 14 13 Thysanoptera 0 0 38 14 12 21 Coleoptera - beetles 63 343 245 51 44 318

- weevils 23 21 12 16 24 31 Diptera 12 6 45 13 6 0 Lepidoptera 0 0 0 2 0 1 Hymenoptera - wasps 3 3 20 12 4 6

- ants 17 16 34 5 52 133 Larval insects 27 17 49 1505 747 1055 Acari * * * 5968 3216 4413 Pseudoscorpionidea 0 2 1 45 66 29 Opiliones 7 4 3 7 1 8 Araneida 16 15 45 55 58 72 Amphipoda 100 91 296 87 44 1201 Isopoda 107 48 5 222 103 181 Chilopoda 1 1 7 15 23 135 Diplopoda 32 32 2 40 43 231 Pulmonata 17 23 0 13 12 4 Terricolae 0 0 2 16 3 18

Total 449 625 831 8610 4766 10089

Litter samples The differences in the number of invertebrates from litter in the two

sites on Hen Island (Table 1) were significant in favour of site A for Collembola (P less than 0.001), plant-bugs (Hemiptera) (P less than 0.005), larval insects (P less than 0.001), mites (Acari) (P less than 0.001), amphipods (P less than 0.001) and isopods (P less than 0.001), and in favour of site B for ants (P less than 0.001) and pseudoscorpions (P less than 0.05).

Comparison of extracted samples from Hen Island and Kapit i Island showed that more Collembola were caught on Kapiti (P less than 0.001), more plant-bugs on Hen Island site A (P less than 0.001), more beetles on Kapiti (P less than 0.001), more ants on Kapiti (P less than 0.001), more larval insects on Hen Island site A (P less than 0.001), more mites on Hen Island site A (P less than 0.001), more pseudoscorpions on Hen Island site B (P less than 0.001), more amphipods on Kapit i (P less than 0.001), more isopods on Hen Island site A (P less than 0.001), more

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Table 2. Number of invertebrates in 02 m 1 of soil samples from site A and B on Hen Island. Figures for Kapiti Island (Moeed and Meads, in press a) are for comparison.

Invertebrates Hen Island Kapiti Island (greater than 5 mm long) A B Te Rere Coleoptera

Odontria xanthosticta A d . 0 1 0 Diglimma clivenoides A d . 0 0 1 Melolonthinae L. 8 10 4

Diptera Tipulidae Pupa 0 0 1 Tipulidae L . 1 0 1

Chilopoda 7 3 1 Terricolae 25 9 2

Total 41 23 10

centipedes on Kapiti (P less than 0.001), and more millipedes on Kapiti (P less than 0.001).

Overall, more invertebrates were caught on Kapiti , followed by site A and then site B on Hen Island (P less than 0.001).

Soil samples More invertebrates were found in soil samples on Hen Island than on

Kapiti Island (Table 2) (P less than 0.001). The difference in the two Hen Island sites was significant also in favour of site A (P less than 0.05). Considerably more earthworms were found at site A than at site B on Hen Island (P less than 0.01).

Table 3. Snails on Hen Island.

Snails Numbers

Liariidae Liarea egea 1

Punctidae Egestula egesta 3 Lamellidia novoselandica 3 Laoma n.sp.* 1 Sericoconcha flemingi 20 Serpho kivi 2 Suteria ide 20 Therasia zelandiae 10 punctid n.sp. 29* 3 punctid n.sp. 55* 1

Rhytidae Paryphanta busbyi busbyi 2 Rhytida tarangaensis 7

* F . M . Climo (pers. comm.)

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Table 4. Invertebrates collected by hand on Hen Island. (*, less than 10 mm long)

Archaeognatha Nesomachilis sp.

Blattodea Celatoblatta sp. Parellipsidion sp.

Dermaptera Parisolabis sp.*

Orthoptera Hemiandrus furcifer Hemideina thoracica Rhaphidophoridae spp.

Phasmatodea Clitarchus sp.

Hemiptera Amphipsalta cingulata Kikihia cauta Kikihia scutellaris

Coleoptera Holcaspis hispida Mimopeus elongata Odontria xanthosticta Pedilophorus chrysopepsis* Stethaspis longicornis Uloma tenebrionoides Xyloteles griseus Zolus sp.*

Diptera Calliphoridae spp. Tipulidae sp. Stratiomyiidae sp.

Lepidoptera Bassaris itea Lycaena salustius Trioxycanus enysii Zizina otis labradus

Hymenoptera Amblypone australis* Discothyrea antarctica* Heteroponera brouni* Mesoponera castanea* Monomorium pharaonis* Vespula germanica

Pulmonata Paryphanta busbyi busbyi Rhytida tarangaensis Serpha kivi Suteria ide* Therasia zelandiae*

Hand collection Invertebrates collected by hand during our stay on Hen Island are

listed in Table 4. Although species differ, most of the invertebrate 224

groups were similar to those found by us on Kapiti Island (Moeed and Meads, in press a).

General Land molluscs of Hen Island have been described by Milligan (1954).

During our invertebrate survey we found 12 species of snails (Table 3). Only one of the endemic Rhytida tarangaensis was a live specimen, and 5 of the empty shells were damaged by rats. The Polynesian rat (Rattus exulans) was present on the island. We found only two empty shells of Paryphanta busbyi busbyi, both damaged by rats.

Table 5. Distribution of likely kiwi food invertebrates in site A and B on Hen Island. Figures for Kapiti Island (Moeed and Meads, in press a) are for comparison.

Invertebrates Hen Island Kapiti Island A B Te Rere

Number of species Beta spp. (Table 3) 4 5 Cicada spp. (Table 3) 3 4 Beetle spp. greater than 10 mm long (Table 3) 6 15 Al l spp. greater than 10 mm long (Table 3) 29 29

Number of individuals Fly larvae greater than 5 mm long/0.2 m 2 (Table 2) 1 0 1 Spiders/0.2 m J (Table 1) 55 58 72 Earthworms/0.2 m J (Table 2)

2-3 mm diameter 13 1 0 4-5 mm diameter 10 8 0 6+ mm diameter 2 0 2 Total earthworms 25 9 2

CONCLUSION

Faecal analysis has revealed that the diet of the little spotted kiwi includes ground wetas, cicada nymphs, adult and larval beetles, fly larvae, moth larvae and some adults, spiders, and earthworms (J.N. Jolly and R.G. Ordish, pers. comm.).

We have compared the occurrence of the known food items of the little spotted kiwi on Hen Island with that on Kapiti Island (Table 5) where little spotted kiwis survive. The number of species in the first part of Table 5 are those recorded for the island as a whole, but the number of individuals in the second part are for the two study sites on Hen Island.

The survey was not comprehensive, but it did provide a series of type-examples against which the island's potential kiwi food resources could be assessed. Although there were more beetle species on Kapiti than on Hen Island (P less than 0.05) and more earthworms on Hen than on Kapiti (Table 5), other likely kiwi food items were about as abundant on

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both islands. This suggests that the food resources would be able to support kiwis on Hen Island.

A C K N O W L E D G E M E N T S

The co-operation and assistance of Messrs R.A. Anderson and J . N . Jolly of the N.Z. Wildlife Service is gratefully acknowledged. Drs M.R. Rudge and J . E . C . Flux helpfully commented on the manuscript. Mrs J . E . Berney kindly typed the manuscript.

R E F E R E N C E S

Barber, H.S. 1930: Traps for cave-inhabiting insects. Journal of the Elisha Mitchell Science Society 46:259-265.

Cochrane, G.R. 1954: Notes on Taranga (Hen Island). Tane 6:20-25. Cranwell, L . M . & Moore, L . B . 1935: Botanical notes on the Hen and Chickens Islands.

Records of the Auckland Institute and Museum 1:301-318. Milligan, E . N . 1954: Land molluscs of Hen Island. Tane 6:120-122. Moeed, A . & Meads, M . J . (in press a): Invertebrate survey of offshore islands in relation to

potential food sources for the little spotted kiwi, Apteryx oweni (Aves: Apterygidae). New Zealand Entomologist

Moeed, A . & Meads, M . J . (in press b): Seasonality of pitfall trapped invertebrates in three types of native forest, Orongorongo Valley, New Zealand. New Zealand Journal of Zoology.

Robertson, N .G . 1959: The climate of New Zealand. In: McLintock. A . H . (Ed.). 'A descriptive Atlas of New Zealand'. Government Printer, Wellington, pp. 19-22.

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