Did You Know ?

1. At the capes Royds, Bird and Crozier colonies, there are about 4 000, 35 000, and 140 000 breeding pairs of Adélie Penguins; about 40 000 breeding pairs reside at Beaufort Island.
2. In the entire Antarctic, there are about 2.5 million pairs of penguins breeding in about 161 colonies, at least as of the mid-1990s.
3. Adélie Penguin colonies are disappearing in parts of
Antarctica but that new colonies are being founded else where? (Click here to learn more about this recent development due to global climate change.)





How Many Adélie Penguins

Adélie Penguins are colonial seabirds. That means they nest close together in colonies, which range in size from about 10 to 170 000 nests. The colonies are at least 2 km apart and each is located in an area accessible from the sea (a beach) and not covered by ice or snow. Within a colony, the nests are arranged in groups, called sub-colonies. These groups usually are on the tops of hummocks and not in the valleys between hummocks. This is because melt water from nearby snow fields and glaciers runs down the valleys, making the ground too soggy for nest building.










Adélie Penguins nesting between two roaring torrents coming from a melting glacier.























Considering all the 161 colonies of Adélie Penguins in the World and assigning each to a size category, we see that only 6 colonies are larger than 100 000 pairs. One of our study colonies, Cape Crozier, is one of these. About 1/3 of colonies have fewer than 1000 pairs, and about ¼ have fewer than 5000 pairs, or the size of Cape Royds. Our other study colonies, Cape Bird and Beaufort Island, are among the larger colonies.










Adélie Penguins nest in groups, called sub-colonies, that are situated atop ridges where snow does not form drifts and where melt water does not run in rivers.


The numbers of breeding pairs of penguins at our study colonies has been changing during the past few decades.

We know the size of the colonies by counting nests with a penguin on it. We also keep records of banded birds, knowing how many each season find a mate and lay eggs. These are the breeding penguins. Those that have a nest but with no eggs are called non-breeders. Many non-breeders make a nest and search for a mate to then breed the following year. For every two breeding penguins there is one non-breeder that is present at the colony during the summer (we know this from banding). There are also other penguins who never visit the colony, until they are at least 2-3 years old. By knowing the ratio of breeding to non-breeding penguins, we can estimate the breeding population of a colony.
It would be impossible to determine the number of nesting pairs in the mass of penguins at Beaufort Island in the photo on the left. This image was taken in late January, when not only are there adult penguins but also large chicks. In order to accurately determine the number of nesting pairs in a large penguin colony, it is necessary to use aerial photos taken on or about December 1, photo on right, when A) only one member of each pair is sitting on the eggs, while the other is off at sea feeding; and B) there are very few non-breeders present. This means that almost all nests with a penguin on it has eggs. Flying at 2000 feet, so as not to disturb the penguins, a series of photos can be taken and then the dots counted. In the picture on the right almost every dot represents a penguin sitting on its nest. Counts by people on the ground at the same time can determine the proportion of nests where there is a non-breeder --- there are usually only a few when aerial photos are taken.







































It is important to have accurate population counts of Adélie Penguins as well as other birds and animals in our world so we know if their populations are increasing or decreasing. As our Earth changes due to climate warming, habitat destruction and human use of resourses the other species we share this planet with must cope. Some species have had to move their homes and change their food sources, others have declined in numbers, and some have not been able to cope and have become extinct, no longer part of our world. Keeping track of Adélie Penguin populations helps us monitor how they are coping with changes in their habitat.To read more about changes in Adélie Penguins habitat click here.



Daily counts of penguins in one sub-colony --- well, except when the weather is bad --- reveal how the number of penguins in a colony changes over time in a spring-summer season. Note that when the aerial photo was taken of this colony, Cape Royds (see photo above), the number of nests with eggs had not changed between Nov 25 and Dec 5, and that the number of penguins just about equaled the number of nests with eggs. After this period the number of nests with eggs slowly decreased, as eggs were lost to skuas. Therefore, the aerial photo taken on Dec 1 showed just the breeding population at its maximum.