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Read by Dave and Charley
Incubation is the act of keeping the egg warm before it hatches. For all our seabirds both the male and female take turns incubating the egg so that it stays warm and both parents can also get a turn in hunting for fish. But the way incubation is done is different depending on the species. Razorbill, guillemot and fulmar all lay just one egg and do not make a nest for it. As we have seen before razorbill and guillemot have specially shaped eggs to stay on small rock ledges whilst fulmars find larger areas to settle on. These three species only lay one egg as that is all they can fully protect without making a nest.
Puffin, storm petrel and gannet all also only lay one egg, but they do not lay them on bare rock surfaces. Puffin and storm petrel lay them in burrows, and storm petrels also nest in rock cavities.
They both only lay one egg because their underground habits of nesting mean they can protect a solitary egg better and increase its chances of survival by putting all their efforts into the on egg. Gannets are too large to nest underground, so they build large nests on the rocks out of dried grass and seaweed.
Unfortunately they can also use fishing nets which will occasionally get a bird tangled in them so we try to stop all dumping of fish nets in our seas.
Gannets only lay one egg because they are so big and powerful, plus they nest in large groups, so they can defend their nest very well and can concentrate all their efforts on just one egg.
Shag and gulls all make nests, but they lay 2-3 eggs. They lay more eggs than our other species because their nests are more exposed than a puffin or storm petrel, they are not as powerful as gannets when defending the nest and they have a nest so have room for more eggs unlike a fulmar or razorbill. Therefore, by laying 2-3 eggs and raising this many chicks they increase the chances of at least one of them surviving.
Back on the 11th of June we conducted the first survey of our common tern colony. This required us to go over to the grass area on a rocky outcrop that they nest on at low tide, as the high tide cuts off the rock from access. Once over there we had to locate and count all the nests.
The nests are very small and made in scrapes in the vegetation. They typically have two to three eggs, although we did find one with 4! This year we located 25 nests. This is excellent news as in 2013 there were 14 and in 2012 there were just 5. So this is a species doing very well at the moment on Alderney. In a months time we will go looking for the chicks and will let you know how many we find.