Posted on 28/04/2015 by Phillip Island Nature Parks

Penguins don't put all their eggs in one basket

Phillip Island’s little penguins exercise a distinct strategy of ‘resource allocation’ in their egg-laying practices, as discovered recently in a study published in the Journal of Experimental Marine Biology and Ecology.

It has long been understood that seabirds are sensitive to the fluctuations in the available food supply in the marine system, and they produce less eggs than other birds. Shearwaters lay only one egg, while many penguins lay two. Some species even lay one normal-sized egg and one tiny egg, as a bit of insurance in case the first egg fails.

Little penguins lay two almost identical eggs and you would be forgiven for thinking that the eggs would have the same nutrient composition, however this recent study by researchers from Spain’s Doñana National Park, Environment Canada and Phillip Island Nature Parks has shed some light on this misconception.

Over 12 seasons, data was gathered from the breeding population here on the Summerland Peninsula. Along with careful measuring, weighing and checking of nests, analysis of the stable isotope levels of blood and plasma samples showed that  the first egg received greater nutrient levels, using resources gained from the female’s steady increase in body weight well before egg-laying.

The second egg was formed with resources gained by the female just before laying, which resulted in significantly lower levels of nutrients. This meant that the second egg was not as ‘good’, giving the chick in the first egg a much better chance of fledging successfully.

This strategy was even more obvious in older penguins that had produced several clutches of eggs in previous breeding seasons. It seems that much like it is in the human world, the older and wiser penguins had learned not to put all their eggs in one basket.

Read the complete Research paper here