Mark Re-capture Pilot Study

In August 2011, the opportunity arose for a short-term mark re-capture study with the assistance of a class of undergraduate ecology students staying on the island for 5 days (4 nights). Because of the danger associated with accessing some areas at night, the study area selected was the same as in the May trial, a relatively open stretch of beach with only low lying rocky outcrops. Over two nights, three sweeps of the same 0.68km stretch of beach were made by groups of researchers and undergraduate students, during which time penguins were captured as they emerged from the water after dark, marked and released. On the third night, one sweep of the beach area was completed where sightings of all penguins, tagged (i.e. recaptures) and non-tagged were recorded.

6.4 Results

6.4.1 Mark Re-capture Trial

In the trial of the methodology in May 2011, over the 12 nights, 69 penguins were tagged, and six re-sighted. Two of the six birds re-sighted had actually lost their original yellow temporary tags and unknowingly were re-tagged. The loss was only later identified as both birds had been flipper banded and their band numbers recorded at the time of tagging. One bird was re-tagged four days after it was first tagged and the second was re-tagged after three days. Previous testing had concluded that if attached properly the temporary yellow tape tags should stay on for approximately two weeks, so in these cases either the tags were not correctly attached or the penguins were able to remove the tags when grooming.

122 The population size using the Peterson estimate was not calculated using these trial data for several reasons that violated the required assumptions. Firstly, the extended trial period was too long for there not to be some immigration, emigration or even deaths. Secondly, there was a higher risk of the tags coming off during the extended 12 day period and finally, there was less chance that the penguins coming ashore were predominantly breeding adults.

6.4.2 Mark Re-capture Pilot Study

Unfortunately, during the August trial, a severe storm combined with high-tide delayed the initial capture by one night and then a low catch rate made it necessary to have a second capture night instead of a non-catch night. The re-capture was then conducted on the fourth and final night. Over the two capture nights, 21 penguins were tagged and released. On the recapture night, 7 penguins were sighted only one of which was tagged. Search effort per unit (including handling time of penguins) was calculated from the number of LP caught divided by man hours. Using these figures the Peterson estimate calculated the Tiritiri Matangi LP population as 147 breeding adults, for the study area (Table 6.1).

123 Table 6.1: Mark recapture data from May trial and August pilot study. Breeding population calculated using the Peterson estimate.

* Temp. tag lost. **Only recapture night.

This estimate relates only to the 0.68km section of shoreline and associated probable nesting area (Site 1, Figure 6.1), i.e. up to the highest point directly above entry point from the sea. This boundary was assumed because it is known that walking on land makes high energy demands on LP (Miyazaki & Waas, 2003) and therefore preferred nest choice would be those available closest to their beach landing site in a direct line. However, in fact, a proportion of nests are found further inland, whether from choice or because of intraspecific competition (Miyazaki & Waas, 2003) is unknown - hence the inclusion of the wider area. Thus the total potential nesting area for Site 1 was calculated as 33.77 hectares. Survey Type Date No. People Searching Search Hours Search Effort # LP Tagged # Tagged LP Re-sighted Total Sighted Pop. Size (Peterson Est.) Trial 8/05/2011 6 2:00 0.667 8 0 8 Trial 9/05/2011 4 2:30 0.800 8 0 8 Trial 10/05/2011 4 2:30 1.000 10 0 10 Trial 11/05/2011 2 2:30 1.800 9 0 9 Trial 12/05/2011 2 2:15 1.111 5 1* 5 Trial 13/05/2011 2 2:00 2.500 9 1 10 Trial 14/05/2011 2 1:40 1.205 4 0 4 Trial 15/05/2011 2 2:00 2.000 8 1* 8 Trial 16/05/2011 2 1:00 0.000 0 0 0 Trial 17/05/2011 2 1:15 0.800 2 0 2 Trial 18/05/2011 2 0:45 2.667 3 1 4 Trial 19/05/2011 2 1:00 2.500 3 1 5 Trial 20/05/2011 2 0:45 1.333 0 1 2 Totals 69 6 75 N/A Pilot 15/08/2011 8 1:00 0.625 5 0 5 Pilot 15/08/2011 9 1:19 0.758 9 0 9 Pilot 16/08/2011 7 1:05 0.926 7 0 7 Pilot 17/08/2011 7 0:55 1.087 0 1 7** Totals 21 1 7 147

124 Figure 6.1: Nesting regions used to estimate total Tiritiri Matangi Island Little Penguin Population. 1) South of wharf to Hobbs Beach, 2) North-west, 3) South-west, 4)

Emergency Landing-Fishermans Bay.

Using the population estimate with additional data, further extrapolations can be made about the total breeding population on Tiritiri Matangi. For example, in the 2011 breeding season within Site 1 there were 15 active nests i.e. nests where penguins were observed occupying/breeding. From the estimate of 147 penguins for this site, this equates to 9.8 penguins per known, active nest. When this figure is applied to other areas where active nest numbers are known nests (Sites 2, 3, and 4 Figure 6.1), a minimum breeding population can be estimated as in Table 6.2.

Table 6.2: Estimate of minimum LP breeding population for selected sites on Tiritiri Matangi Island.

Region

Number Tiri Region

LP per Nest # Active Nests in August 2011 Total Estimate 1 Wharf/Hobbs 9.8 15 147 2 North West 9.8 24 235 3 South West 9.8 11 108 4 East Coast 9.8 11 108 Total 598 1 1 2 1 3 1 4 0.68Km Hobbs Beach Wharf

125 This extrapolation gives an estimated adult breeding population of 598 LP from the four sites identified on Tiritiri Matangi Island in 2011. The estimate cannot be applied to the whole island, as some areas are not easily accessible and therefore were not surveyed.

For such breeding population estimates, Dann & Cullen (1990), suggest there could be up to a further 60% of non-breeding juvenile birds dispersed away from the island.