Two Eggs!

The second egg was laid yesterday (May 23) between 2:30 and 2:35 pm. That’s about sixty hours after the first egg. Loons typically lay a two egg clutch with a day or so between eggs. It is believed that the separation in time increases the chances of having at least one chick survive to fledge.

Here’s the reasoning: Chicks have different dietary needs from adults. The availability of suitable chick food  will vary from lake to lake and year to year. Some years, there may only be enough food to successfully raise one chick. The loon parents indiscriminately feed the first gaping beak they see. If there are two chicks competing equally for a limited amount of food that can only sustain one chick, then both chicks will be compromised; their chances of survival will be poor.

But if one chick is hatched a day or two before the other chick, it will be a little ahead in development and be the dominant chick. It is much more likely to be fed first. In times of low resources, the development of the second chick is likely to fall further and further behind that of the first chick and eventually succumb to starvation or even be pushed out of the family by the dominant chick.

Yes, this sounds harsh, or even cruel, but in the context of population viability it makes sense. It’s better to sacrifice one chick than to lose both chicks. And keep in mind that this is strictly a contingency. There’s an excellent chance that this experienced loon pair will be able to feed both chicks.