The chicks continue to develop rapidly on all three nests. On Nests 1 and 2 they are peeping over the edge quite often. They move their heads from side to side – a behaviour called qualitative stereopsis which Paul described in a 2013 post on his Wildlifewriter blog. Here is Chick 1 on Nest 2 demonstrating the behaviour. He is looking at 37 on the camera pole.
The ungainly wings seem to grow ever longer and the primary feathers are coming along well. The feather sheaths appear blue because they are filled with blood which supports the feathers by, in effect, “hydraulic pressure” until they grow and stiffen.
Lots of preening helps the feathers out of the sheaths.
The weather has been less windy on the whole and ample fish are coming to the nests. Mealtimes can last an hour or longer with short breaks by one or both chicks before extra room is found.
At this age the chicks are much better at regulating their own body temperature. In the warmer weather, they engage in “gular fluttering” – a rapid cycling of the throat muscles which exchanges heat by evaporation.
Mrs YA has exhibited some interesting behaviour too. She picked up a long piece of bark and for over five minutes tore tiny pieces off. Here is a short segment.
Ospreys use bark to maintain their beaks and may get nutrients and/or trace elements but usually this is intermittent not sustained behaviour.
There have been intruder incidents on all nests – intruders unseen – but the oddest was on Nest 1 when the intruder dropped a stick onto the nest. Obviously s/he felt a helping hand was required!
Many thanks to Paul for his input on avian ecology.