n.v.m. wrote:
some very interesting shots. how do the parents know who has been fed though.
Thank you,
That is an interesting question. There are about 500 terms couples in this colony and each couple has two to 5 chicks. When an adult flies back from the sea with a fish, they have to pick out there nest and chicks and chicks from other nests run over and try to get a fish yet somehow they manage to feed there chicks. I believe they are able to recognise there chicks and feed them yet it could simply be the colony feeds everyone. While the chicks look similar to us, if you look closely, there are differences and the adults probably see the differences.
a couple of comments - terns are closely related to gulls and gulls have been studied for their localization abilities
- if a human moves an egg a short distance away from that gull's nest, it will recognize its egg and nest and roll the egg back in even against a background of sand and other nest scrapes
- but if the distance the egg is moved is just a bit further, the parent thinks it is another gulls egg and eats it
so, there is some sort of spatial map that birds have that is very effective but has a very sharp cutoff compared with one a mammal might have
as to the 2 chicks, sibling competition is common in terns, gulls, herons, etc. - the parent's fitness is best served by getting at least one chick to survive and both if possible; but the stronger chick (usually older) has less investment in its sibling than the parent does
