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Cuckoo, September (1 Viewer)
- Thread starter Earnest lad
- Start date
lou salomon
the birdonist
juvenile, cannot be sexed.
Earnest lad
Well-known member
Thank you 
Sorry to persist, but please may I be advised: which aspects indicate juvenile?
Sorry to persist, but please may I be advised: which aspects indicate juvenile?
BobbitWorm45
Well-known member
One of the things is that it was in September. Adults will have returned to Africa by this time.
lou salomon
the birdonist
basically the broad white fringes.
KenM
Well-known member
Thank you
Sorry to persist, but please may I be advised: which aspects indicate juvenile?
Also the brown wash to the upper-parts.
Cheers
Earnest lad
Well-known member
Thank you everyone for those most helpful tips, for future reference.
SteveClifton
Well-known member
KenM
Well-known member
Yes I’ve seen “hepatic” Cuckoo in Cyprus during April, don’t know what the incidence might be during September in the UK...?
SteveClifton
Well-known member
The question EL asked was about how to separate adults from juveniles Ken.
I'm no expert, but this paper (http://www.jolyon.co.uk/research/publications/Kolecek%20et%20al%202018%20cuckoo%20chick%20colour.pdf) indicates that in eastern Europe as many as 25% of adult females are rufous in colour.
Sample size in that study was not huge, but in the following link, there is an indication that in Germany at least 14% of females could be rufous: https://www.birdforum.net/showthread.php?t=245275
The incidents of such rufous/brown adults in September is perhaps a topic for another debate, but for sure, the presence of brown tones in Common Cuckoos is no way to separate adults from juveniles.
This link seems to indicate that subtle brown tones are much more common in adult females than the field guides would have us believe, since they typically only illustrate grey adult males: https://www.flickr.com/photos/timmelling/42121491431
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Deb Burhinus
Used to be well known! 😎
just to add to the most obvious feature mentioned by Lou, also juveniles have dark irises (turning to bright yellow in adults) as photo shows, along with pale patch on the nape which is quite visible in the field.
Adult females are grey with varying amounts of buffy or rufous tinges to the throat and upper breast however the rufous morph adult female is unmistakably a very rich reddish brown and gives a very different impression of ‘rufous brown’ imo from juveniles in the field due to the lack of pale fringes or compared to ‘grey’ adults in the field that may show limited buff/brown - one of my old forest patches use to hold a rufous morph female (as distinct from a grey morph brownish female) who looked stunning, especially in sunlight.
I had a link somewhere on the possible reasons for polymorphism in females ..
here it is - it makes for interesting reading
https://www.nature.com/articles/s41598-019-44024-6
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Earnest lad
Well-known member
rollingthunder
Well-known member
A juvenile at that time of year should have a subtle ‘scaly’ appearance to the upperparts due to pale edging of the feathers and the pale nape spot is usually a feature that is easily seen in the field particularly on a perching individual imo.
Good birding -
Laurie:t:
Good birding -
Laurie:t:
Earnest lad
Well-known member
Thank you. I appreciate the tip about the pale nape which was new to me and now I know that I shall be able to keep my eye open for that in future o
