Friday, 27 December 2013

Brown Treecreepers: 
How to tell their age and sex

I am building up a portfolio of photographs which show how to age and sex various species of Australian birds. These will be posted in a separate blog, but for now I will upload them to this site and would be grateful for any comments prior to collating them on the new site. The birds have all been caught in mist-nets during long-term field studies, mostly run and organised by Mark Clayton or Richard Allen, to whom I am grateful for their knowledge in confirming the birds' plumage patterns, particularly some of the more tricky species.

As a sample of how I intend to progress with the project, here are a few images to aid people in aging and sexing Brown Treecreepers Climacteris picumnus, following differences in their plumages.

Adult (1+) male Brown Treecreeper
04/11/2012, West Wyalong, NSW.
The bird on the left is an adult male, categorised  as 1+, a bird of one or more years old. It is recognisable as an adult by the bold eyestripe and breast markings. The sex is determined by the black freckle spots arranged in a necklace around its throat. The throat's rich buff-orangy colouring is also indicative of age, although more comparative and less useful as a guide if only one bird is seen at a time.

The dark dashes on the breast feathers are the brown edges to the breast feathers which have a wider band of white/buff down the shaft than in those of birds in their first year. Therefore the dashes on the adult birds are farther apart.

First-year (1, juvenile) male Brown Treecreeper
15/12/2013, West Wyalong, NSW.
The bird on the right is a first-year male,
categorised as a 1 juvenile, as it still has folds of skin around the base of its bill, the remains of its juvenile gape.

Again, it has a black necklace of spots. Females, adult and juveniles/first-year birds, have rusty-red spots on their necklace.

First-year birds of both sexes have narrower dark-fleck patterns on their breast feathers. This being due to narrower bands of white along the feather shafts than on adult birds.

The same adult male
When the adult's head is seen from the side, there is a distinct contrast between the prominent eyestripe and buff supercilium, highlighted by a faint white top edge. These markings on the first-year bird are less obvious, as is the contrast between the grey tail tips and the rest of the tail, which in the adult is strong due to the darker upper tail colour. There is a similar difference between the dark primaries and primary coverts of the adult and the grey/brown colour of those of the first-year bird. 

When seen close in the hand, the tips of the adult bird's greater coverts are faded and frayed, while those of the first-year bird are fresh with buff tips. This last point is also a useful diagnostic feature for aging birds of many other species and will be repeated when applicable in further aging and sexing of birds notes as I compile them.

The same  first-year, juvenile.

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