The arrival in late autumn of Goosanders locally is a sure sign winter is on the way and the adult drakes, with their combination of red bills, glossy green-black heads and glowing, salmon-pink underparts are easy to identify and surely make this species one of the most attractive ducks on the British list.
With the drakes stealing all the limelight, little attention is paid, however, to ‘redheads’, the term used to describe adult females and first-year birds of both sexes. Given reasonable views, in many instances it is possible to age and sex certain individuals. Two photos of ‘redheads’, both taken locally yesterday and kindly sent to me by the photographers, prompted a bit of research and illustrate this nicely. The first was taken by Clive Bowley at Pitsford Reservoir. The clean white, extensive and sharply demarcated chin and throat, along with the darker lores and dark iris, make this an adult female.
Compare this with the one below, which was photographed at Abington Park Lake, Northampton by Keith J Smith www.kjs-images.com. This individual has a much more diffuse area of white restricted mainly to the chin, there are a few small blackish feathers beginning to appear on the throat (difficult to see) and there is a blackish half-collar at the base of the chestnut on the side of the neck which clinches this as a first-winter male. The outer part of the iris is pale which is also a feature of juveniles and many males.
Clive’s image also shows the serrated edges of the mandibles, which gives the genus Mergus the collective name of ‘sawbills’.