penguin data 2001 2003

DATA OF THE ST KILDA PENGUIN STUDY GROUP 2001-2003

Rachael Nolan © Earthcare St Kilda

INTRODUCTION

The little penguin or fairy penguin (Eudyptula minor) can be found on the islands of New Zealand and Australia, with the centre of distribution located in Bass Strait (Stahel and Gales 1987). The St. Kilda population is considered to have originated from the Phillip Island colony, but is now a self-sustaining colony (Cullen et al. 1996). The first nesting penguins were recorded on the St. Kilda breakwater in 1974, with the first research into the colony beginning in 1986 (Strachan 2001). The breeding season is triggered by food availability and usually begins in spring and is completed by January (Roseby 1997). Shortly after this the penguins prepare for their annual moult which sees them increase in weight in readiness for the two to three weeks when they cannot go to sea (Strachan 2001).

This report examines trends in the data collected about the St. Kilda colony from two seasons spanning from May 2001 to April 2003. Data collected covered the number of adult penguins recorded on the breakwater; the weight of the adult penguins that were captured; and the number of chicks that were recorded on the breakwater

DATA COLLECTION

The St. Kilda penguin research group, managed by Earthcare, generally meets twice a month after sunset to conduct research into the colony on the breakwater. This involves walking along the rocks using a torch to locate penguins. When a penguin is found its location on the breakwater is recorded along with any relevant information such as how many penguins can be seen or heard, if there are chicks or eggs present, or if the bird appears to be moulting. If possible the penguin is caught and taken to the top of the breakwater where further information is collected including weight, sex, identification number and any other general comments. The identification number can be found either on a stainless steel band on the right flipper or by scanning below the back of the head for a microchip. If no band or microchip is found then the penguin is microchipped. Banding of penguins took place from 1986 to 2001, while microchipping began in August 2002.

Research takes place all year round with the season beginning in May and continuing to April the following year. Across a season the search effort can vary with both the number of people involved in the research and the experience of those researchers varying. This may influence the data that is collected.

Data was averaged for each sampling night and graphed for each month. The number of penguins recorded on the breakwater refers to both those that were captured, seen and reliably heard. T-tests were used to determine if there was any significant difference between the average male and female weights for each year. Analysis of variance (ANOVA) was used to determine if the weights for each sex varied across each season.

FINDINGS

NUMBER OF ADULT PENGUINS ON BREAKWATER

The highest number of adult penguins recorded on the breakwater for both seasons generally occurred during the breeding period. For the 2001-2002 season the highest number (84) was recorded in December (refer figure 1). While for the 2002-2003 season the highest average number (105) was recorded a month earlier, in November (refer figure 2). This season also recorded a second peak in June with one sampling night recording 108 penguins either seen / heard or caught. This contrasts to June the previous season where only 53 adult penguins were recorded on the breakwater.

Figure 1: Number of adult penguins recorded on breakwater for each month of the 2001-2002 season.

Figure 2: Number of adult penguins recorded on breakwater for each month of the 2002-2003 season.

The lowest number of adult penguins recorded on the breakwater in both seasons occurred in late Autumn / Winter. During this period the penguins have less reason to come ashore as the moulting period has finished and the breeding season is still some time away. The lowest number recorded for the 2001-2002 season occurred in July with only 22 adult penguins recorded (refer figure 1). While in the 2002-2003 season the lowest number recorded occurred in May with an average of 55.5 recorded for that month (refer figure 2).

The total number of adult penguins caught on the breakwater in 2001-2002 was 129 that were banded and 69 which were unbanded. In 2002-2003 this figure was 179 which were banded / microchipped and 40 which were not

WEIGHT OF ADULT PENGUINS

The average weight of adult penguins on the breakwater for both seasons shows the weight of the males to be significantly higher than that of the females (p<0.05, refer appendix 1). The average weight of the penguins across both seasons varied little with respect to time of year (refer figures 3 and 4). Although some variation is noted during the moulting period which is considered to begin in January / February for the St. Kilda colony (Strachan 2001). For example in the 2001-2002 season the average weight of the penguins for each sex varied significantly with respect to the time of year (refer appendix 2). The differences relate to a significant increase in weight between January and April (refer appendix 3). In February an average weight increase of over 400 g was noted for adult females, while an average weight gain of over 100 g was noted for adult males. During the following February the average weight gain for males was 200 g while there was no appreciable weight gain for females (refer appendix 4 for average weights of each sex in each month).

Figure 3: Average weight of male and female adult penguins in 2001-2002 with standard error bars shown.

Figure 4: Average weight of male and female adult penguins in 2002-2003 with standard error bars shown.

The average weight for each sex was similar across both seasons. Variation is noted in the weight range recorded across both sexes in each season (refer table 1).

	Weight Range (g)	Average Weight (g)	Standard error (g)
Male (01-02)	850-2100	1261.98	15.59
Female (01-02)	800-2150	1185.44	24.87
Male (02-03)	900-1900	1280.13	18.59
Female (02-03)	700-1940	1125.13	14.75

Table 1: Weight range and average weight recorded for adult male and female penguins at the
St. Kilda colony across 2001-2002 and 2002-2003.

CHICKS RECORDED ON BREAKWATER

In both seasons the first recorded chicks on the breakwater occurred in August and by March virtually no chicks were recorded. In 2001-2002 there were two peaks in the total number of chicks recorded on the breakwater, the first occurred in September with a peak of 33 chicks recorded on one night. The second peak occurred in January with a total of 28 chicks recorded on one night (refer figure 5). The following season had only one peak in the number of chicks recorded, however this was more sustained than in the 2001-2002 season. This peak occurred from November through to January with the highest number of chicks recorded in a night being 39, which occurred in December (refer figure 6). This data may indicate that in the 2001-2002 season there were two breeding cycles with high numbers of chicks recorded two months earlier than in the following season.

Figure 5: Number of chicks recorded on breakwater (including seen / heard and caught) in 2001-2002.

Figure 6: Number of chicks recorded on breakwater (including seen / heard and caught) in 2002-2003.

CONCLUSION

When the study into the colony of St. Kilda penguins began in 1986-87 an average of 19 adult birds were recorded per visit. This increased to 44 in the season before the 1995 pilchard crash, in 1996-97 the average number recorded dropped to 22 (Blake 2001). Since this time the average number of adult birds recorded per visit has increased dramatically to 57 in 2001-2002 and 71 in 2002-2003. While some increase in the numbers recorded may be due to the increase in the number of researchers taking part in the search it is worth noting that in the 2000-2001 season a significant increase in the adult penguin population was recorded but there was no corresponding increase in the search effort (Blake 2001).

The data collected from the 2001-2002 and the 2002-2003 seasons shows that the within the St. Kilda population the weight of adult males is generally heavier than that for adult females. The average weight of the population remains steady across each season except for during the moulting period when a weight gain is noticed. No significant variation in weight is noticed during the breeding season.

Trends in chick production for the St. Kilda population varied across the two seasons. In 2001-2002 breeding began earlier in the year than in the following season which allowed for two spikes in chick production. The following season the later start in breeding corresponded to only one spike in chick production.

ACKNOWLEDGEMENTS

I would like to thank Andre Chiaradia, Phillip Island Nature Park, for his assistance with some of the data analysis in this report and for his comments on the manuscipt.

REFERENCES

Blake, N. (2001), St. Kilda Penguin Report, June 2000 - June 2001.

Cullen, M., N. Blake and M. Bickham (1996). Urban penguins. Nature Australia. Winter: 23 - 28.
Stahel, C. and R. Gales (1987). Little penguin, Fairy penguins in Australia. Kensington, New South Wales University Press.

Munroe, S. (2003), Marine Mammals and little penguins: existing ecological conditions in Port Phillip Bay - 22nd July 2003, for Melbourne Corporation Channel Deepening Project

Roseby, C. (1997), Wild Things: Fauna of the City of Port Phillip, Earthcare St. Kilda Inc

Strachan (2001), The St. Kilda Penguins, Earthcare St. Kilda Inc.

APPENDIX 1

T-test results for difference in weight between male and female adults:

Season	p-value	df	CI
2001-2002	0.010	196.1	95
2002-2003	0.000	226.9	95

APPENDIX 2

ANOVA table for differences in weight for each sex with respect to month for the 2001-2002 season.

Dep Var: WEIGHT N: 262 Multiple R: 0.561 Squared multiple R: 0.315

Source	Sum-of-squares	Df	Mean-square	F-ratio	P
Sex	457831.467	1	457831.467	11.702	0.001
Month	3301814.558	10	330181.456	8.440	0.000
Sex * month	998105.422	10	99810.542	2.551	0.006
Error	9389541.248	240	39123.089

APPENDIX 3

ANOVA table for differences in weight for each sex with respect to month, excluding the moulting period from January to April, for the 2001-2002 season.

Dep Var: WEIGHT N: 153 Multiple R: 0.521 Squared multiple R: 0.272

Source	Sum-of-squares	Df	Mean-square	F-ratio	P
Sex	455581.734	1	455581.734	25.103	0.000
Month	206137.463	6	34356.244	1.893	0.086
Sex * month	253043.586	6	42173.931	2.324	0.036
Error	2522687.263	139	18148.829

APPENDIX 4

2001-2002 weight data (in grams).

Month	Male	Standard Error	Female	Standard Error
May	1265.5	31.4264	1103.75	36.64197
June	1183.077	1183.077	1088.182	45.10227
July	no data	no data	no data	no data
August	1313.333	41.51183	1100	66.36838
September	1177.667	28.16984	1186	33.23987
October	1176.364	14.97105	1056.667	46.88046
November	1192.308	37.05771	37.05771	62.75526
December	1197.778	63.02067	985	39.27922
January	1283.75	78.23813	1209.091	60.75965
February	1385.625	56.73013	1614.545	121.2163
March	1394.706	72.96311	1257.895	72.75923
April	1239.286	47.00321	1056.923	20.98182

2002-2003 weight data (in grams).

	Male	standard error	Female	standard error
May	1258	62.76588	1183.182	50.11928
June	1162.727	38.61443	1071.667	30.59593
July	1266.25	38.21637	1177.778	34.71222
August	1231.429	46.82432	1087	31.55419
Sepember	1260	185.8315	1228.571	93.08032
October	1246.923	26.34545	1076.364	30.03278
November	1255	35.74955	1127.5	36.64583
December	1249.167	36.7518	1089	23.4285
January	1361.875	60.06398	1223.077	90.66269
February	1486.667	109.2601	1095.667	64.08415
March	1348.75	114.8825	1098	77.90022
April	1293.333	110.9554	1135	61.15678

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