Eggs and chicks!

The breeding season at Año Nuevo Island is underway!

As I write, Rhinoceros Auklets and Cassin's Auklets are incubating their one egg of the season. Rhinoceros Auklets only lay one egg per year, choosing evolutionarily to put great effort into the survival of one chick a year and the longevity of adult birds. Cozy in its underground burrow, the chick avoids the many dangers of the above-ground world, such as predation and nasty weather.

Cassin's Auklets also lay just one egg per clutch, but in really "good" food years, they will take advantage of the situation and lay another egg after their first chick has fledged (fledged = grown up and successfully left the nest). We've already seen our first Cassin's chick this year, so they are already off to a good start.

This little Cassin's chick above is actually from the Channel Islands, where the breeding season begins earlier--but that's what they look like.

Western Gulls are also laying eggs in earnest. Most pairs have laid 3 eggs, which is their normal clutch size. By laying three eggs, the gulls are evolutionarily acknowledging the many threats that await their young, during both the egg and chick stage. A gull pair that successfully fledges three chicks has done an impressive job of parenting--most are lucky to have one or two survive.

A historic problem for gulls and their chicks at Año Nuevo Island is a lack of ground cover where their chicks can hide. Exposed to the elements, the chicks are vulnerable to predators and the aggressive territorial behavior of neighboring gulls. Many gull chicks get in trouble when they run too far from their nest and have nowhere to hide.

This spring, however, there are hiding spots aplenty! After our restoration effort to re-establish native plants on the island, there is a good cover of grasses for the chicks to hide in. The gulls also are using the new plants to make bigger, better nests than before.

The photos at above show a typical plant cover around the gull nests in 2010 (above), and a typical gull nest in 2011 (below).

Pelagic and Brandt's cormorants are also currently on eggs. Auklets use a slow-and-steady, conservative strategy to ensure the success of their one egg, but cormorants do pretty much the opposite! These species have a highly flexible, highly adaptable breeding strategy. In a "bad" food year they may choose to not breed at all, but in a "good" food year, they'll lay up to 5 eggs! If conditions are somewhere in the middle, they'll adjust egg number accordingly.

Sometimes even in the span of one summer, the cormorants will have several "pulses" of egg laying, depending on oceanic conditions at the specific moment. So far it's not a boom or bust year--we're somewhere in the middle in terms of number of nests on the island and so far it seems to be around a "3-egg year."

Right now it's eggs, but pretty soon it'll be chicks! Stay tuned for more photos.