Learning about penguins is cool
Jed | July 16, 2009This year for Christmas I adopted a penguin named Lucky in Nicole’s name from the International Penguin Conservation Work Group. We get pictures and updates about our penguin every other month. This past month’s update had fewer details about our specific penguin than normal since they are on “winter break”. Instead, this last update gave a great overview of the penguin chick lifecycle and the negative effects of human activity on their survival rates. Below is this month’s update, reprinted with permission from Mike Bingham of the IPCWG. At graphs referenced by the update are located at the bottom of this post.
With the penguins away the colony is now completely deserted, and the winter rains and winds slowly erode away the nests with no adults around to keep them in good repair. One season of egg-laying and chick-rearing has come to an end, and in a few weeks a new season will begin, so it is a good time for us to summarise the results of last season’s work.
Colonies in both Chile and Argentina were very similar last season, as you can see from the attached graphs. Along the bottom of each graph is the date, starting at the moment that egg-laying has occurred, and ending when the chicks finally leave the nest to begin life on their own. Down the left-hand side of the graph is the scale showing ‘Egg and Chick Survival’ in percent (%). This is showing how many of the eggs originally laid still survive, either as eggs or chicks.
It begins at 100% at the time of egg-laying, because no eggs laid have yet been lost. As the days pass (moving from left to right across the graph) some of the eggs are gradually lost, due to bad weather or being stolen by skuas (large seagulls), and so the percentage of eggs surviving begins to drop. This continues after the eggs hatch too, as some of the chicks also die from bad weather and predation. The black vertical line between the words ‘Eggs’ and ‘Chicks’ marks the average hatching date for the colony.
Eventually the chicks leave the nest to begin life on their own. The graph ends at this point, and the percentage of eggs surviving now is showing how many of the eggs originally laid grew up to become healthy chicks that left the nest. Remember that the dates are averages for the whole colony, and may not necessarily be the same as Lucky.
Some egg and chick losses are natural and impossible to avoid, but the success of the colony is determined by how high these losses are, and whether or not the losses are avoidable, caused by human activities, or due to natural factors. If you take a look at the graphs for Chile and Argentina, you will see that they are both very similar. Of all the eggs laid at the beginning of the season, in both countries about one quarter (25%) were lost by the time the eggs hatch, and about one half (50%) by the time the chicks left the nest to begin life on their own. Each nest begins with two eggs, so with half the eggs (50%) going
on to produce a healthy chick, that means an average of about 1 chick per nest, which is good. This indicates a healthy colony.
The other indicator that these colonies are healthy is where along the graph the losses occur. Virtually all egg losses are the result of bad weather, predation by skuas, inexperienced parents, or other natural factors. In years when egg losses are low or high, it is almost without exception the result of good or bad weather, so these are natural factors which lie beyond the control of man.
The period immediately after the eggs hatch is the same, with these small defenceless chicks mostly dying as a result of bad weather, predation, or careless parenting, which are all natural factors. In a healthy colony, once the chicks become big enough and strong enough to survive bad weather, or being trampled by a careless parent, their only real threat to survival is lack of food. So in a healthy colony, chick losses should slow down once the chicks become older, which is what we see in both Chile and Argentina.
In both Chile and Argentina the graphs are virtually flat within a month after hatching, which means that chick losses are virtually zero after this point. Virtually all the chicks that reach two or three weeks of age go on to leave the nest, because they are receiving plenty of food to keep them fat and healthy. This is thanks to good management in these colonies, and to the no-fishing zones placed around these colonies to prevent commercial fishing boats taking away the food that the penguins need to raise their chicks.
The international scientific community called on the wealthy Falkland Islands to set up similar no-fishing zones to protect penguins in the year 2000, but the Falkland Islands Government refused. The Falklands graph for last season shows clearly how this decision is affecting the penguins. In the Falkland Islands we see the same fall in survival resulting from natural factors affecting the eggs and small chicks, but this decline keeps on going even as the chicks get older. The reason for this is that the commercial fishing
industry takes away so much of the fish and squid which these penguins need to feed their chicks, that the chicks simply do not receive enough food to survive. As a result the overall survival rate in the Falklands is around half a chick per nest, approximately half that of Chile and Argentina.
Even this is not the full story. The one chick per nest surviving in Chile and Argentina are fat healthy chicks weighing around 3.3 kgs, whilst the half a chick per nest surviving in the Falklands are weak and underfed, weighing an average of 2.6 kgs. Chicks leaving the nest weighing less than 3 kg do not usually have enough body fat reserves to survive the first few weeks of life, during which they must learn to catch their own food, with nothing more than their fat reserves to sustain them. So in reality very few of the chicks in the Falklands survive to reach maturity.
With virtually no juveniles returning to replace the adults, the Falklands population has declined by around 90% since the onset of commercial fishing in 1988, as adult penguins die from old age and are not replaced by youngsters. Thankfully populations of these penguins are safe and protected by more caring governments in Chile and Argentina, otherwise the species would be under severe threat.
My apologies for the fact that this report is harder to follow than most others, but I feel that at least once a year it is important to present to you the science that lies beneath the work we do. You can find more information about our scientific studies at www.seabirds.org/resume.htm
- Mike Bingham
Graphs showing Egg and Chick Survival over time for Argentina, Chile, and Falklands:
If you are interested in reading more about the plight of the Falklands penguins compared to their Chilean and Argentinian brethren, see the following two scholarly reports:
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