Blackcap age (1 Viewer)

Jon Turner · Jan 23, 2011

I ringed this Blackcap as a 5M in my garden this morning, and as you can see from the photos, it is showing a lot of brown in the black crown. Much more than I would expect after post-juvenile moult last year. I also ringed a more normal male with just a hint of brown on the forehead.

Anyone seen this feature in winter Blackcaps before?

DMKSlater · Jan 23, 2011

5M for me, lot of black tho as you say.

Dave

grahamarchy · Jan 26, 2011

DMKSlater said:
5M for me, lot of black tho as you say.

Dave

this is not uncommon in blackcaps. They often have feathers of the brown/orange colour admixed in with the black cap. Some have browny tips to the feathers that wear down over the winter to leave a shiny black cap when the time comes for breeding. so it is worth looking under the tip colour.
in your pictures where the feathers part you can see that they are black underneath with a browny tip.

still a clear male. although 5 ing it based on these picture is impossible.

Jon Turner · Jan 26, 2011

grahamarchy said:
this is not uncommon in blackcaps. They often have feathers of the brown/orange colour admixed in with the black cap. Some have browny tips to the feathers that wear down over the winter to leave a shiny black cap when the time comes for breeding. so it is worth looking under the tip colour.
in your pictures where the feathers part you can see that they are black underneath with a browny tip.

still a clear male. although 5 ing it based on these picture is impossible.

Thanks both, I aged it as a five on shape of tail feathers.

I hadn't seen one with this much brown on the black cap before and I have done lots of Blackcaps in my garden in winter over the last 16 years.

John Morgan · Feb 1, 2011

Jon Turner said:
Thanks both, I aged it as a five on shape of tail feathers.

I hadn't seen one with this much brown on the black cap before and I have done lots of Blackcaps in my garden in winter over the last 16 years.

You didn't mention the extent of greater covert moult. With such a lot of juvenile feathers in the cap, one might have expected an interesting number of ogc.

Mark Grantham · Feb 3, 2011

This variation is quite normal, if uncommon, in Blackcaps and these will be proper adult-type feathers rather than retained juveniule feathers.

grahamarchy · Feb 4, 2011

i agree with Mark - i have seen these tipped feather on age code 6 before, so most likely to be adult type feathers with orangey tips and black bases rather than retained Juvenile feathers. Interesting variation though.

Jon Turner · Feb 4, 2011

Praps I'll change it to a 6 then! I can't get a net up in this wind to see if I can retrap it! Strange that it had very pointed tail feathers.

grahamarchy · Feb 5, 2011

it could well be a 5. the juvenile versus adult feathers usually refers to those grown in the nest (juvenile) and those moulted after fledging (adult type). The argument here was that the bird could either have retained some feathers on its head that it grew in the nest or it could have grown these feathers- that show the orange colour after the first moult. The main point is that you cannot tell the age from the head alone. using the tail shape and Old Greater Coverts id features will give you an accurate age.

Motmot · Feb 5, 2011

grahamarchy said:
it could well be a 5. the juvenile versus adult feathers usually refers to those grown in the nest (juvenile) and those moulted after fledging (adult type). The argument here was that the bird could either have retained some feathers on its head that it grew in the nest or it could have grown these feathers- that show the orange colour after the first moult. The main point is that you cannot tell the age from the head alone. using the tail shape and Old Greater Coverts id features will give you an accurate age.

Yep very true, not a problem for a 5. Check this individual aged 5 on plumage which showed a mixed cap on April 20th:

John Morgan · Feb 5, 2011

While I would prefer not to muddy the waters any more, it needs to be said that in some passerines with sexual plumage dimorphism, old females have been recorded showing some male characters. I can't put my hand on any references just now, but perhaps somebody here can help.

I've only seen it once, in a putative female Red-backed Shriike that was half-way to male. I say putative, but as it was autumn bird not in its hatching year, a male should have been considerably better marked.

Jon Turner · Feb 5, 2011

John Morgan said:
While I would prefer not to muddy the waters any more, it needs to be said that in some passerines with sexual plumage dimorphism, old females have been recorded showing some male characters. I can't put my hand on any references just now, but perhaps somebody here can help.

I've only seen it once, in a putative female Red-backed Shriike that was half-way to male. I say putative, but as it was autumn bird not in its hatching year, a male should have been considerably better marked.

I did partially think I should have made the original question one of both age and sex. I didn't have the courage to mention gynandromorphism, but is it possible here?

John Morgan · Feb 7, 2011

Jon Turner said:
I did partially think I should have made the original question one of both age and sex. I didn't have the courage to mention gynandromorphism, but is it possible here?

I'm not sure we could propose gyandrotrophism for this bird as there does not seem to be the usual left-right division that typifies that condition.

I see no reason to reject the idea of older female Blackcaps getting some degree of black in the crown feathers. An increasing ratio of male hormone is presumably the reason why the brown feathers of juvenile males are replaced with black (and perhaps a little brown) during the pj moult at 1- to 3-months-old. If that same change of ratio occurs in females, but much more slowly than in males, or if production of female hormone declines with age as it seems to in mammals, then who knows...

One of the great things about science is recognising there exists stuff we don't yet know. It not only keeps us on our toes, but it also stops the subject from becoming boring

What a pity there is no known way of ageing most passerines after the first post-breeding moult takes place in their 2nd calendar year of life.

ESTEBANNIC · Feb 7, 2011

John Morgan said:
While I would prefer not to muddy the waters any more, it needs to be said that in some passerines with sexual plumage dimorphism, old females have been recorded showing some male characters. I can't put my hand on any references just now, but perhaps somebody here can help.

I've only seen it once, in a putative female Red-backed Shriike that was half-way to male. I say putative, but as it was autumn bird not in its hatching year, a male should have been considerably better marked.

True in Sardianian warblers. We have ringed "old" females that could pass for males with dark heads.

Blackcap age (1 Viewer)

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