amazing penguin South America update

Dear PenguinPromises

By now Promises and friends will be arriving in southern Brazil. Some penguins will remain there during the winter whilst others will continue further north as far as Rio de Janeiro. So while our penguins are away enjoying their winter migration, it seems a good time for me to share with you our research results for the breeding season that has just finished.

The graphs attached might look complicated to people not familiar with graphs, but I will explain it all step by step so it should be easy to follow. I attach three graphs which show breeding success for each of our three study colonies, Cabo Virgenes (Punta Dungeness) in Argentina, Magdalena Island in Chile and the Falkland Islands. During October, after the penguins have laid their eggs, we begin following the progress of our adopted penguins at each site, and that is when each graph begins.

Let me begin by saying that the symbol "%" is the same as the word "percent", and it actually means how many out of every 100. So 100% means 100 out of every 100, which is the maximum possible, and 50% means 50 out of every 100, etc.

Immediately after egg-laying in October there have not yet been any eggs lost, because the eggs have only just been laid, so the breeding success at that stage is still 100% (the maximum). This is shown on the graph. In the bottom left-hand corner of the graph it says "Oct 2018" and in the upper left-hand corner the line of the graph says "100".

Going along the graph from left to right you have time passing by from October onwards, and going from top to bottom you have "% of eggs and chicks surviving"
going from 100% at the top down to zero at the bottom of the scale. As time goes by some eggs are lost so the breeding success starts to drop below the maximum of 100%.

As time goes by (moving from left to right) eggs get lost for a number of reasons, and the line of the graph starts to drop below 100% as more and more eggs are lost. The main reason for eggs getting lost is that one of the partners does not return to the nest at the proper time. This is especially common in new couples breeding for the first time.

After egg-laying the adults take turns at incubating the eggs. One sits on the eggs keeping them warm, whilst the other goes out to sea to eat fish. They usually change over every two or three days so that both adults do not have to go for more than a few days without food. However occasional one of the penguins loses track of time, or has trouble finding the nest, and does not return at the proper time. Our studies show that the adult left waiting in the nest will hold on for about 6 days for the partner to return, but is then forced to abandon the nest to go to sea for food. With the eggs left unprotected gulls quickly steal them, causing the nest to fail.

Another common cause of egg loss is bad weather. The adults do their best to protect the eggs from rain, but heavy rain can cause the eggs to get cold, and if they get too cold they stop growing and fail to hatch.

So as the days and weeks go by breeding success declines for a number of reasons as we move from left to right across the graph. Eventually the chicks are fully grown and fledge, which is at the right-hand side of the graph. That is the final result for breeding success.

Fledge is a word which really means the point at which a young bird begins to fly, but since penguins cannot fly, then for penguins it means the point at which the chicks finally leave the colony to begin life on their own.

So beginning with the graph for Argentina, you can see on the right-hand side of the graph that 58% off all eggs laid produced a healthy chick that left the colony. That is to say that for every 100 eggs laid the colony produced 58 healthy chicks, which is excellent. Each nest has two eggs so that is 58 chicks for every
50 nests, well above one chick per nest.

A breeding success of 50% (1 chick per nest) is excellent, and more than enough to maintain a healthy colony, so 58% is really good. This colony located between Cabo Virgenes and Punta Dungeness is very healthy.

Eggs losses are part of the natural process and cannot be avoided, so a decline in breeding success at the beginning of the graph is usual. If there is a good supply of food then the graph should level off about half way along the graph, which is exactly what we see for this colony. Well fed chicks do not die for no reason, so if the chicks are well fed and well cared for, then the second half of the graph should level off, which is what the graph for this colony shows.
In general, if the graph levels off in the second half then the colony is healthy.

Taking a look at the graph for Chile, the graph declines much more steeply in the beginning because more eggs were lost in this colony this year than usual.
The reason was extremely bad weather during the egg incubation period. At Cabo Virgenes the penguins make their nests under bushes, whilst on Magdalena Island the penguins nest in burrows dug into the ground. Usually burrows provide much better protection from the rain than bushes, but last season was an exception.

During November and December 2018 both Cabo Virgenes and Magdalena Island had very heavy rain, which caused egg losses at both colonies. However on this occasion the rain was so heavy that on Magdalena Island the rain began running along the surface of the ground and into burrows. Some burrows were flooded and others weren't, all depending on the slope of the ground around each burrow.

I have been studying the penguins on Magdalena Island since 1998 and this is only the second time that I have seen this happen. The last time that this happened was in 2002. As I said previously, burrows usually provide better protection from rain than bushes, but on these very rare occasions the penguins living under bushes at Cabo Virgenes lost fewer eggs than the penguins in burrows on Magdalena Island.

However despite the heavy egg losses, the colony on Magdalena Island still finished with a breeding success of 38%, which although not as high as expected, is still not bad. Each nest has two eggs, so 38% is almost 8 chicks for every 10 nests, which is enough to sustain a healthy colony. Penguins are also long-lived, breeding for about 25 years, so a few poor seasons makes no difference to the colony as a whole.

The problem is when breeding success is low every year, such as in the Falklands.
The graph for both Argentina and Chile level off during the second half of the graph, as they should, because the chicks are well fed. However the graph for the Falklands shows that breeding success continues to decline right through to the end of the graph. That is because the Falklands fishing industry takes so much food that the penguins have trouble catching enough food to feed their chicks. The chicks are therefore underfed and many do not survive to fledge.
The graph is also longer because with less food the chicks' growth is slow. Despite hatching at the same time the chicks in the Falklands fledge in April instead of January or February.

This is nothing new. We presented out findings to the International Penguin Conference back in the year 2000, and virtually the entire penguin research community sent the Falkland Islands Government a petition requesting no-fishing zones around major penguin colonies in the Falklands. Sadly the Falkland Islands Government continue to refuse this protection, and the penguin population in the Falklands has declined by over 90% since the fishing industry was established in 1988.

You may be wondering why the graphs continue to drop because of egg loses long after the average hatching date shown on the graph by the black vertical line.
The main reason for this is that when eggs get cold and stop growing, the adults do not know that the eggs will not hatch, and continue to incubate the eggs long after the hatching date. Only when the penguins finally give up and abandon the nest does it finally get scientifically recorded as egg losses, which is why many egg losses are recorded well after the hatching date. The dates shown on the graph are also an average for the whole colony, so the actual dates for Promises may be very different.

I will write to you again in a few weeks time, and by then the penguins will have begun their journey back home to the colony to begin the new breeding season.

Best wishes, Mike