in the newspaper '
Helsingin Sanomat' there was an article on May 1st (yesterday) about the suppositios about ospreys 'mating-for-life' and 'fidelity-to-one-spouse' being uncovered to be a false belief.
A Finnish ornithologist Matts Finnlund has examined an extensive amount of web cam picture material from both the Hailuoto and the Nauvo nests from previous years. he has discovered that the male, arriving to the nest first and thus conquering the territory, mated with one female after another as they arrived at the nest. he thinks that the females left the nest when the male stopped bringing food to them and had thereafter been replaced by another female arriving later. he thinks that another possibility is that a later arriving female had expelled the earlier female.
above i tried to give a short resume of the article's content, which i think was very interesting. i would assume that the male tries to conquer a territory and a nest which is as appealing as possible (meaning as favourable for breeding as possible). the females arrive later and fly around checking the available selection of territories and males and evaluate their abilities of feeding (they go 'nest shopping' and check which male has 'the biggest pay check'). during this checking period the birds mate, too. maybe if the eggs don't start to develop the female moves on... (in the olden days in the countryside in Finland a young human couple spent nights together with their their families consent till the girl got pregnant, even though it was 'a sin' in the eyes of the church. only after the pregnancy was noted, the couple was married, because a marriage without offspring was useless.)
it is possible that the females have a fights over the best bachelors (competition about the most able males in the darwinian sense). on the other hand, the males may choose among the females, too. a male may not feed a female if he 'thinks' she is not attractive enough. the female 'understands' the hint and leaves to look for a more favourable male.
as more information is obtained it seems that the monogamy of birds is only human wishful thinking...
maybe BSs behave in a manner somewhat similar to the ospreys? who knows... maybe all the ladystorks found mates more south this spring and that's why Padis is alone now. (i think we all agree that Padis and his nest are handsome enough even for a more demanding taste...

) these web cams really give valuable information about the behaviour of wild birds, impossible to obtain in any other way!
