As mentioned in the post of 9 June, Sooty Terns began nesting early in 2019, but it had been thought that the earliest eggs, laid around 10 May, had been deserted. Our discovery yesterday (13 June) of the first 2019 chick shows that some of those mid-May eggs did survive and that this year’s hatch has begun.
Our monitoring of incubation at nest sites that we have marked and visited daily, has suggested that food supplies around Bird Island are proving difficult for the birds to find this year. At each nest site, one member of the pair incubates the egg while the other goes fishing. When the bird that has been fishing returns, the other bird leaves the colony in search of food. When food is abundant, changeovers at the nest occur every 1-2 days, but if food is scarce the incubating bird can be left for longer. This year, most incubation shifts have lasted around three days, with one bird remaining at its nest for 8 days before being relieved by its mate.
If this apparent food scarcity lasts through the chick-feeding stage, chick survival could be reduced – time will tell.