Eggs, Experience, and Survival

“How many eggs do penguins lay a day?”

Annabel (Year 1, Opoho School) asked that wonderful question a few months back. I love how children always go with what they know and work from there. Annabel’s experience with eggs is the chicken variety, and she knows a hen lays a lot of eggs. Not more than one a day, perhaps, but if her needs are met and she gets 13 to16 hours of light (and doesn’t go broody and sit on her eggs) she can lay an egg nearly every day. With a false sun (i.e., lightbulb) you can fool your hens into constant laying even during the darker months of winter.

Nesting box. Changing of the guard...Photo by Rosalie Goldsworthy.

Although the hours of light per day are important for penguins, it is more for knowing when it’s the right time to breed. Penguins do eggs differently than domesticated chickens that have been bred to lay lots of eggs. Unlike hens, penguins spend a huge amount of energy raising their chicks. Because raising chicks takes so much effort they only lay a few eggs per year. Our yellow-eyed penguins usually lay two eggs per year but some penguins lay two eggs and raise one chick (one egg is sacrificed), others lay one egg and raise one chick, and in warmer climates penguins may lay two eggs and raise two chicks. If food is plentiful for these subtropical penguins, they might lay another clutch to raise four chicks in a year. Still, as far as egg laying, penguins are nowhere near the chicken.

The key factor for fledgling survival with yellow-eyed and other penguins is parental experience. Experienced penguin parents who know how to find food, avoid predators, and return to the nest with enough food for their chicks, raise fatter chicks. And the fatter the chick, the better it fares when it goes out to sea for the first time. A few yellow-eyed penguin researchers have shared their thoughts on what they call the “super breeders” in a yellow-eyed penguin colony. These birds are the gold of the colony because they consistently raise two chicks successfully, well into old age. When you know your colony and run a penguin hospital, your super breeders are the birds that you take extra special care to see that they stay healthy. Both Hiltrun Ratz at Penguin Place and Rosalie Goldsworthy at XXX do just that.

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