Sunday, 26 January 2014

How to age and sex Rufous Whistlers

Two Rufous Whistlers - but what age and sex are they?
Charcoal Tank, NSW. March 2010
I have recently been in correspondence discussing how to age and sex Rufous Whistlers Pachycephala rufiventris, so considering that they are one of the most widespread bird species in Australia, I thought I should post a simple guide to this dilemma. 

The problem arises from their plumage moult sequence over the first years of their life. For they take three years to attain full adult plumage, and during the first two years, the males and females are alike (to our eyes and criteria so far discerned). Do the birds know which sex each other is, I'm sure they do, so why can't we tell?

This is not a complete description, indeed there might be errors. However, during future banding trips, I hope to photograph birds of known age (from previously banded birds) and note details which will help to further understand how to age and sex these common birds. The page will then be updated as fits new points to consider.  

Juvenile Rufous Whistler
Charcoal Tank, NSW. January 2011

Juvenile (J) Rufous Whistlers are recognisable by their bright yellow gape, the skin at the base of their bill, light-coloured bill and heavily streaked breast. These are usually being closely attended by adult birds.

Eye - dark brown iris

Bill - pale grey upper mandible, pink/yellow/grey lower  
         mandible, orange yellow inside

Breast - buff and heavily streaked

Throat - grey streaked with dark grey

First-year or Immature  Rufous Whistler
Charcoal tank, NSW. Sept 2012

First-year (1 or 2-) birds, or immature, those in the first year of their life have a similar plumage to the juveniles and adult females. Also the sexes are indistinguishable. The orange/yellow inside of the bill is the most diagnostic feature when in the hand, but not so useful in the field. Then, the pale lower mandible below the darker, but not dark black bill is the best feature to look for.

Eye - brown

Bill - dark grey on top mandible, pink/brown lower mandible.

Breast - pale buff streaked with dark grey.

Throat - grey streaked with dark grey/black.

Adult female Rufous Whistler (3+)
Charcoal tank, NSW. Nov. 2012

Adult female (3 or 3+) birds can be recognised by their black bill, dark red iris and lightly streaked breast. Their throat is white rather than grey as in a first-year bird. However, second-year males (2), i.e. those more than one year since hatching, look very similar. Banded birds can be aged with reference to when previously caught, otherwise behaviour is perhaps the only clue to sex in the field. In spring and summer try to determine whether the bird is behaving like a male or female. And beware of this piece of confusing knowledge - male Rufous Whistlers (and females?) can breed in their second year while in sub-adult plumage or in that similar to females.

Eye - dark deep red

Bill - black top, lower, and inside, pale palate

Breast - light rufous streaked with dark grey

Throat - white, streaked with dark grey

Sub-adult male Rufous Whistler
Charcoal tank, NSW. Sept 2012

Second-year, or sub-adult male (2) i.e. those more than two years since hatching, but less than three. These birds show the beginnings of adult male plumage coming through the immature plumage which was similar to that of a female. A dark grey or black breast band spreads across the top of the breast, and black feathers come in around the face. The throat whitens and loses its streaks. And the iris is red, but not as bright as that in an adult male's eye.

Eye - dull red

Bill - black on top, lower and inside, pale palate

Breast - rich rufous, with narrow dark streaks, faint or
             incomplete breast band

Throat - white and lightly streaked, dark feathers
              around face

Adult male Rufous whistler
Charcoal tank, NSW. Sept 2012 

Adult male (3 or 3+) Rufous Whistlers are the easiest to identify, not only to species but to sex. They have a distinctive rufous breast, belly and undertail coverts, a bright white throat and a black breast-band with linked black feathering up the sides of the throat and across the face. The eye is bright red and the bill glossy black.

Eye - rich red iris

Bill - black top, lower and inside

Breast - rich rufous with a black breast-band

Throat - pure white

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