Reports about the colony

Mike Cullen presented his analysis in 1989. It gives a detailed description of the site and penguin population. Click here  ST KILDA PENGUINS J.M . Cullen. (pdf)

This was followed by a series of reports some of them covering the rebuilding of St Kilda Breakwater. These reports are in pdf format.

St Kilda Penguin Research Report 1992  Mike Cullen

Penguin Report 1995-6  Mike Cullen/ Neil Blake

ST KILDA PENGUIN RESEARCH REPORT 1996 Mike Cullen/ Neil Blake

October 10 1996 Mike Cullen/ Neil Blake

Penguin report Jan 1997 Mike Cullen

ST KILDA PENGUIN RESEARCH REPORT 1998-2000 Mike Cullen/ Neil Blake

Stage Four  reconstruction  of the St Kilda Breakwater. Neil Blake May 1998

Penguins 2001-2003 Rachael Nolan

Penguin report 2004 Zoe M Hogg

PENGUIN REPORT 2005  Zoe M Hogg

PENGUIN REPORT 2007-08  Zoe M Hogg

PENGUIN REPORT 2008-09  Zoe M Hogg

Penguin report 2009-10  Zoe M Hogg

Symposium presentation  Zoe M Hogg (Power point as pdf)

Penguin Report 2010-2011  Zoe M Hogg

penguin report 2011-12 Zoe m Hogg

Penguin Report 2012-13 Zoe M Hogg

penguin report 2013-14

 

Penguin Report 2016/17

During June we celebrated 30 years of St Kilda penguin study. Mike Cullen and Neil Blake started looking at the colony and recording penguin habitation during 1986.Ten years later they were still out there every second Sunday.

 

During September we held a symposium where all aspects of penguin life in St Kilda were presented by a variety of different research projects.

With the new marina now in position it is interesting to see that the penguins have modified their evening visits to the breakwater by coming in between the breakwater and the marina in a group and can easily be seen powering down the strip of water separating the two.

The colony is growing. You will see from the set of numbers below that we had 312 breeding sites this year which gave us an estimate of the population around 1400 penguins.

We do not manage to catch all the chicks, some are buried deep in the rocks. When they do return and are chipped some of them show as females but later as males as they grow and their beak size increases. Sex is identified by the size of the beak as all reproductive organs are buried in the body.

penguin year 2010/11 2011/12 2012/13 20013/14 2014/15 2015/16 2016/17
number ofsites with evidence of breeding

175

270

208

233

298

281

312

number chicks chipped

38

125

86

118

156

212

128

chipped males

62

37

44

45

64

63

96

chipped females

97

76

85

95

100

91

129

chipped female later male

19

14

21

17

23

9

5

actual male/female new penguins 81/78 51/62 65/64 62/78 87/77 72/79 96/129

At the moment we are getting a lot of penguins from 2015 coming in and pairing up now that they have grown old enough to start a family.

We caught 942 penguins during the year and microchipped 295 adults and chicks. They started breeding in May with eggs in nests, there were chicks by June and lots of chicks by July. By late December most chicks had fledged and their parents started to moult.

Times caught.   Number of penguins.

1…………………………..569       The number of penguins caught 8 or 9 times  were single males. Maybe

2…………………………..189        they had little else to do. We have 5 penguins dating from 1999-2004,

3……………………………102       they are alive and well and producing chicks. They have already paired

4……………………………..42        up with much younger penguins and settled into well prepared nests.

5……………………………..21

6………………………………..9

7………………………………..6

8………………………………..3

9………………………………..1

The following analysis was done by Thommaso Bendoni

Chick Return Rates:

It would be beneficial to know what proportion of the chicks born in the colony every year return to settle in the colony. However, we cannot reliably test this as the main potential cause for error is the fact that an untagged chick counted on one occasion may be caught and tagged on a later occasion. This would mean that the untagged chick runs the risk of being counted both times, i.e. as un-tagged and as tagged, which would affect the reliability of any estimate for the total number of return chicks to the colony.

It would also be interesting to find out the average time that passes between the chicks’ first capture and their first re-capture (the latter of which could be interpreted as their first return to the colony). With this in mind, I went ahead and created an exhaustive list of all the tagged (whether by Band or Microchip) chicks in the colony in the past 10 years. With this list, I then found their initial capture date: basically, when they were born, give or take a few weeks. I then also found the corresponding date on which each penguin was re-captured for the first time. I created a chart to demonstrate this as percentage of captured chicks first recaptured within given time periods.

The chart shows that well over half the total number of chicks caught are re-captured within the first 12 months, the next highest rate coming the following period (2 to 3 years) after first capture. So, it appears that the chicks tend to return to the colony within 2 years, with a few stragglers coming back after 3. After that point, we can be fairly sure that if a chick has not yet returned, it likely won’t ever – whether that may be because it has found a spot in a different colony, or it has been eaten by a shark, we can’t know.

A total of 1411 chicks were tagged in the period for which I had data (Beginning of 2007 to April 2017), 522 of those returned to the colony at some stage. 364 of those that returned did so after more than 10 weeks since first capture, which indicates a known rate of 69.7% for chick reaching fledging stage. If this is applied to the total number of chicks (1411) caught in the last 10 years, we can estimate that 983.92 (let’s round up to 984) chicks born in the St Kilda colony reached fledging age – a staggeringly large number.

The next chart shows most common rates observed for the last recapture of chicks.

 

 

Over 70% the chicks caught in the last 10 years were last seen after less than one year. The following three years share similar final recapture rates. The overall relationship between chick’s final recapture and time is very similar to that observed for chicks’ initial recapture and time. Basically, this second graph reinforces the message that after the first year, we are unlikely to see the chicks again.

As the total number of penguins in the St Kilda colony is not known to be decreasing (on the contrary, from what I gather, it’s ever-growing), we can come to the assumption that the colony may be of importance to surrounding populations of blue penguins, other colonies.
The chart below demonstrates the time that passes between a penguin’s first capture (whether as chick or adult) and the last time it is spotted.

The total number of tagged penguins in the last 10 years is 4008. The total number of penguins that have not been caught since initial tagging is 1689, which is roughly 42% of the total number of penguins with an ID This means that well over half of the penguins that are caught and tagged (whether by band or chip) return to the colony.

 

Again, the trend is very similar to those observed in the previous two charts. The vast majority of tagged penguins are known to return to the colony for up to 4 years before never being recaptured again.

This suggests that the penguin population at the colony is very variable, in that the same individuals do not spend their entire lives here. Rather, it seems to support the idea that this colony is a good area for breeding and chick rearing (as we have seen from the high success rates with chicks reaching fledging age!) So, my hypothesis would be that penguins come to the colony to temporarily make it their home in order to breed, then they leave. Whether they leave because there is competition for space, or for any other reason, I wouldn’t be able to hazard a guess – I would need to study some literature. Thomasso Bendoni.

All is well in the St Kilda penguin colony and they will have extra protection during the coming months with a new fence and gate.

Zoe M Hogg

6 thoughts on “Reports about the colony

  1. Hi, yesterday there was a penguin that looked pretty bad. It was covered in oil and appeared non healthy.

  2. Are you sure it was oil? There are a few penguins on the breakwater that have not moulted properly and are in the process of dying. This is a natural occurrence that happens every year during moult season. They try to swim but just get very wet shaggy feathers that have half fallen out. They look awful but then I doubt if we look good when dying. They may be very old, or may have not got themselves in to good enough condition and well fed before moult.

  3. Hi,

    Isn’t there also the presence of an otter-like Australian native called a Rakali at the breakwater? Why doesn’t there appear to be research done on these animals? I had never heard of them prior to going to the pier last year, and presume they are relatively rare. Shouldn’t this necessitate a more urgent need for research and protection along with the penguins?

  4. Yesterday I found a dead penguin on a beach in Sandringham, not close to the waterline but up in the bushes. There is an area of rocks similar to the breakwater rocks which is there to stabilise the hill above. I’m wondering weather the penguins are attempting to establish a colony there. Sadly, the penguin had been mauled but not eaten and it’s head was missing. Should this be reported to anyone and followed up?

  5. Thankyou for your concern. The most likely thing that happened to your penguin is that it did not survive the stressful time of moult. This is the time of the year when penguins die and turn up on our beaches. it was probably brown or white not the usual blue.

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