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Golden Gate Park
San Francisco CA
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9:30 am – 5:00 pm


11:00 am – 5:00 pm
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10:00 – 11:00 am

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Live Penguin Cams 

May 14, 2011

African penguin Reproduction: Egg Management and More Candling


The management of African penguin eggs includes marking eggs, record keeping and candling (as reviewed in previous blogs). Knowing when eggs are laid assists the staff in planning for expected offspring. Because African penguins lay 2 eggs usually 3-4 days apart it is important to differentiate between the eggs. Sometimes that is done by size (often the first egg is larger), however it may be difficult to tell by size.  Marking the eggs with a pencil is useful in egg management. Above are 2 eggs, one is marked with an Alpha (upper left egg in photo) designating the first egg. The second is marked with a Beta. As eggs develop, the air cell (located at the fat end of the egg) enlarges and eventually tilts. The air cell is seen upon candling. By drawing the edges of the air cell on the outside of the shell, staff can predict that the egg is close to hatching. The chick draws it’s first breath of air into their lungs in this air cell- this is called the internal pip. Within 12 hours they begin to externally pip (break through the egg shell). Records are kept for each time the eggs are candled and are especially important very close to the internal and external pip. This is called the pip to hatch interval. Writing on the eggs, record keeping and candling are important management tools for chick survival. Below are three candling photos, the first photo is of an African penguin egg at 19 days into incubation, second photo is 34 days into incubation and the third is 38 days. The dark area is growing bacteria likely post mortem, compare this to the previous penguin blog photo when the embryo and blood vessels were obvious at 9 days into incubation.-Pamela Schaller

penguin-eggs-candled-Day 19-compressed

African penguin egg: Day 19

penguin-eggs-candled-Day 34-compressed1

African penguin Egg: Day 34


African penguin Egg: Day 38

Filed under: CAS Penguin Colony — Penguins @ 4:19 pm


  1. Hello, My name is Aiden and I am 4 years old. I am very interested in penguins so I asked my mommy to email you a question. Are African penguins the same as a black-footed penguin? Also, how do you tell King penguins from Emperor penguins? Thank you so much! Aiden

    Comment by Aiden Fleming — May 17, 2011 @ 1:58 pm

  2. we have enjoyed watching the eggs on the nest cam. when do you expect them to hatch?

    Comment by Julie — May 20, 2011 @ 9:32 pm

  3. What is the incubation period (due date?)

    Where in the view of the enclosure is this nest located?

    Comment by Lynn — May 21, 2011 @ 7:54 am

  4. Hi Lynn, We have experienced a 37-38 day incubation in African penguins; however, literature suggests a 37-42 day incubation. These are first time parents in a new exhibit and are “loose” incubators (stand up frequently). These varaibles affect incubation time and frequently lead to poor hatch success the first time. If the eggs hatch; they are due within the next five days. This is burrow number seven located on the right side of the exhibit (as a guest would view the exhibit).-Pamela Schaller

    Comment by Penguins — May 21, 2011 @ 9:44 am

  5. Hi Julie, See the response to Lynn’s question above.-Pamela Schaller

    Comment by Penguins — May 21, 2011 @ 9:48 am

  6. Hi Aiden, Yes, Black-Footed is another common name for the African penguin. However, African penguin is considered the most accepted common name. Emperor penguins are much larger than King penguins and breed only on the Antarctic Continent. King penguins have larger orange markings on the sides of their heads and throat.-Pamela Schaller

    Comment by Penguins — May 21, 2011 @ 9:55 am

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