South American update

Dear PenguinPromises

The penguins have arrived back home after their winter migration to Brazil.
Here in the southern hemisphere we are now into Spring, which is the time of year for the penguins to lay eggs and raise chicks.

Magellanic penguins live to about 30 years of age, but do not begin breeding until they are 5 years old. That is the time when they develop the distinctive black and white lines, which distinguish the adults from juveniles that are still too young to breed. It takes 5 years for the penguins to develop strength and stamina, and to learn how to become experts at catching fish, which is very important for being a good parent. Feeding hungry chicks is very demanding and even the strongest adults loose around one quarter of their body weight during the chick-rearing process.

Our penguin colony lies on the beach along the Straits of Magellan, right on the border between Chile and Argentina. When I began my studies here in 2003 the colony was only in Argentina, but the colony has grown in size under our protection, and has now spread over the border into Chile. Some of the penguins now live in Chile and some live in Argentina, even though they are all part of the same colony. The penguins live in between two lighthouses that are barely 15 kilometers apart. They have the lighthouse of Cabo Virgenes in Argentina to the North East, and the lighthouse of Punta Dungeness in Chile to the South West.

The Straits of Magellan is rich in fish stocks, making it a perfect place for raising penguin chicks. So each year the penguins return in October to lay eggs and to raise another generation of chicks.

The first thing that the penguins do when they arrive home is find their partner. The pairs do not travel together when they go to sea on their winter migration. At sea there are no landmarks for the penguins to meet up again when they get separated chasing fish. Distinguishing individual penguins out at sea is almost impossible, so the pairs do not even try to remain together. They each go their separate ways during the migration, and then meet up again back at the nest in October.

Each pair has their own home to return to, and just like humans they meet up again back home. The only difference is that for these penguins that home is a bush. Their bush is where the couples reunite after the winter migration.
After meeting up again they then have to make a new nest. The nest is really just a hollow in the ground, but the penguins make the nest under their bush to get protection from the weather, and from seagulls that might try to steal their eggs.

Each year the penguins must make a new nest, because whilst they are away the old nest fills up with soil and dead leaves, and other garbage. Each year they make their nest in a slightly different location, to keep away from fleas and other blood-sucking parasites that lie dormant in the old nest lining waiting for the return of their hosts (the penguins).

Your penguin and partner finished their nest a few days ago, and now they have laid two eggs. The couple must now keep the eggs warm by lying over them, so that the heat from their bodies keeps the eggs warm. The embryos growing inside the eggs are the bird equivalent of human pregnancy. The embryos have their food supply provided by the egg yoke, and they receive oxygen through tiny pores in the egg shell. The pores are just large enough to allow oxygen and carbon dioxide to pass through the egg shell, but just small enough to stop water and bacteria from entering. (That is why eggs from the supermarket last so long without refrigeration). All that the embryos inside need to grow into baby penguins is to be keep warm, and safe from predators.

Penguins always lay eggs and raise chicks as pairs. Being a parent is hard work, and too much work for a single penguin to manage on its own. The eggs take more than 6 weeks to hatch, and the parents have to lie over the eggs the whole time to keep the eggs warm and safe.

The eggs are on land in the nest, and the fish that the penguins eat are out at sea, so you can see the first problem. When the penguins are incubating the eggs they cannot eat anything. Six weeks is a long time to go without food. However with two penguins sharing the work they can take it in turns.
One penguin incubates the eggs whilst the other goes out to sea to catch fish. Then they change over every two or three days. That way both penguins get to eat at least once every few days, and the eggs are kept nice and safe until they hatch.

The main cause of egg loss is a partner taking too long returning to the nest, forcing the penguin in the nest to abandon the eggs to get food. Our studies show that this occurs when the penguin out at sea is away for more than about 6 days. The main reason for a penguin returning late is that it has been unable to find fish as quickly as usual, and therefore continues hunting until it is properly fed. Penguins in the colony lay their eggs almost the exact same date each year, so with that amount of precision during the course of a year, it is unlikely that a penguin could simply loose track of time whilst out at sea for just three days.

Nature has its strategies for optimizing the survival of each species.
Magellanic penguins are long-lived birds that invest a lot of time in preparing to breed. They do not even attempt to breed until they are 5 years old, and once they do begin, they have about 25 years of egg-laying and chick-rearing ahead of them. Survival of the species dictates that it is more important for the adults to remain healthy and well fed, even if it means loosing the eggs and having to wait another year to raising chicks.
The adults have many years of breeding to compensate for the occasional year of breeding failure, provided that they do not sacrifice their own health.
The adults must conserve their weight during the incubation phase, to be in good physical condition for the rigorous chick-feeding phase that is to come.

This occasional delay in returning to the nest, to the point of causing the nest to be abandoned, is more common in young penguins breeding for the first time. First time parents have less experience in knowing where to look for fish, and are not as good at catching fish as the more experienced penguins. Nevertheless this is a good area for penguins to find fish, so breeding success is usually high here in this colony, even for young parents.

I attach a new photo of your penguin in the nest incubating the eggs. I will write to you again in a few weeks when the eggs finally hatch.

Kind regards, Mike