We have had some really hot weather since I wrote to you last. Some days the temperature has been more than 30 degrees Celsius, which is very unusual for this part of the world. We are not used to such hot weather, and the penguins do not like such extreme heat. If the chicks had been smaller at the time some of them might have succumbed to the heat, but thankfully they were already on the brink of leaving the colony when the heatwave began. I attach a photo of the penguins sheltering under a bush to get out of the sun.
Most of the penguins in the photo are adults, but on the left you can see two juveniles. You can tell them apart from the adults because they do not yet have the white line of the adults. That line only appears when the penguins reach
5 years of age. These juveniles are between one and four years old but it is impossible to be more exact. In the background in front of the fence post there is also a solitary chick which has not yet left the colony. The chick is healthy and well fed so there is no need for concern.
Most penguins in the colony lay their eggs at about the same time, but there are always some couples that lay eggs much later than the others. They are usually young couples nesting for the first time, and begin late because of the delay in finding a partner and building a new nest.
A couple of weeks ago the two chicks that Promises raised finally left the colony to begin life on their own. They will now be slowly making their way up the coast of Argentina heading towards Brazil, where they will find bright sunshine to help them catch food. So now Promises can finally relax and recover the weight lost over the last few weeks.
When penguins are not incubating eggs or raising chicks, it is easy for them to catch enough food to feed themselves. They do not need to return to their nest every day, because they can just sleep out in the ocean where the fish are.
They are free to follow the fish wherever they go. Now Promises can wake up each morning with breakfast ready and waiting, but it was very different when there were eggs or chicks to look after.
The fish live in the ocean, but because penguins are birds they have to make their nest on land just like other birds. Fish and other cold-blooded aquatic animals are able to lay eggs in the water, because being cold-blooded they need very little oxygen, and are able to obtain what little they need directly from the water. However warm-blooded animals need a lot more oxygen and are not able to get enough from water.
There are many warm-blooded animals that live in water, such as whales, dolphins and penguins, but they all need to come to the surface occasionally to breathe air for that very reason. Birds have to breathe air, and so do their eggs. Eggs are not impermeable as one might think, the shell is actually porous and allows the embryo inside to breathe. That would be impossible if the eggs where laid in the water like fish.
Cold-blooded animals like fish are also able to lay eggs in the water because the eggs can develop at low temperatures, but warm-blooded animals can only survive if they keep warm. Bird eggs have to be keep warm until they hatch, which is impossible in cold water
For these two reasons birds have to make their nests on land, where there are no fish. So right from the start Promises must spend time and energy travelling long distances backwards and forwards between where the fish are and where the nest is.
Not only do the penguins have to travel a lot after laying the eggs, they are also only able to eat once every two days. Penguins always lay eggs and raise the chicks in pairs. One of the penguins has to stay on land keeping the eggs warm and safe, whilst the partner is out at sea feeding. They take turns of course, but even so instead of eating fish every day, from the moment that the eggs are laid Promises can only eat once every two days, so each parent can only eat half as much as they did before.
Once the chicks hatch things get even harder. Much of the food that the parents catch is given to the chicks when they get back to the nest. The parents have to get up early in the morning, and swim 25 miles to where the fish are, catch as much as they can during the day, and then swim 25 miles back to the nest to feed the hungry chicks in the evening. After feeding the chicks they then have to groom the chicks to remove fleas and ticks. On a good day Promises might get
6 hours of rest before setting off again.
It is rather like a human couple having a baby, and from then on instead of getting up each morning to enjoy breakfast together, the parents have to run
25 miles to the supermarket to buy fresh milk and food, and run 25 miles back home to feed the baby. What parent would not loose weight doing that every day?
Before egg-laying Promises weighed over 6kg. Now that the chicks have left the colony that has dropped to just 4kg. The parents loose one third of their body weight raising chicks. Of course the penguins never complain.
They are driven by their natural instinct to make this sacrifice for their chicks, just like most parents.
Most of the chicks that have recently left will not return to the colony for
5 years. They remain much further north, off the coast of Brazil where there is more sunlight in winter. A few do return to the colony in summer, like the juveniles in the photo, but for most it is not worth making such a long journey south until they are ready to breed at 5 years of age. Perhaps the juveniles in the photo have returned to the colony to spend time with their parents, who may well be under the bush with them.
Each year people ask if they can adopt the chicks. I wish we could offer the chicks for adoption, but unfortunately we can’t. We would not be able to send any news or photos for 5 years.
The chicks eventually return to raise chicks of their own where they were born, and I expect that they even remember the location within the colony where they lived as youngsters. That would mean that the chicks often nest close to their parents when they return to lay eggs, and would almost certainly remember each other. It is likely that Promises will get to meet the chicks again at some point in the future, and may even end up nesting side by side.
Now it is time for Promises to rest and relax out at sea. The exhausted parents find a nice spot where there are lots of fish, and will remain there for a few weeks until they have completely rested and recovered their weight. When they do finally come back to the nest it will be to go through the annual moult (molt), but I will explain all about that in my next letter in a few weeks’ time.
Best wishes from Mike