I have managed to study 3 Moorhens over the past few months. The first one back in July was a young juvenile whose flight feathers were only about half grown (unfortunately no pictures). The next two were netted at Arnot Hill Park in Arnold with the help of Chris one of the park rangers. Both were hatched this year (age code of 3). Hopefully the photos show the development and progression through the partial post juvenile moult of the body feathers ('Moult in Birds' by Ginn & Melville).
The first bird, FS03241, was caught in September and is showing a mixture of white and brown/grey feathers on the belly and breast, off white under the chin, upperparts olivaceous brown with little sheen and a greyish- brown iris.
The second bird, FS03242, was caught in October and has less white on the underparts, though still marked, and the upperparts show a mixture of juvenile brown and adult type ash- grey feathers especially on the head and nape. The iris is pretty red, by January it should be crimson. This bird has a wing length of 185mm which indicates it may be a male.
The 9th primary feather was narrow and pointed on both birds. ('Identification Guide to European Non-Passerines' by Baker) Neither bird had the red band on the legs or the red and yellow bill as seen on adults.
This is part of the on going study of the birds of Arnot Hill Park and our thanks go to Chris and Michael, the park rangers, and to Gedling Borough Council for their support.