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Post by Tringa on Aug 21, 2015 10:32:43 GMT
Interesting info and comments Alan. I can understand the confusion between pigeons (though for me more with feral pigeons) and raptors. I have been misled quite a few times by a glimpse of a greyish pointed winged, fast flying bird that turned out not to be the raptor I'd hoped for.
I haven't heard of kestrels flying through fences but many years ago I heard a radio programme where someone had seen a goshawk hunting by flying through a stock fence.
Dave
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Post by accipiter on Aug 21, 2015 15:02:00 GMT
Interesting info and comments Alan. I can understand the confusion between pigeons (though for me more with feral pigeons) and raptors. I have been misled quite a few times by a glimpse of a greyish pointed winged, fast flying bird that turned out not to be the raptor I'd hoped for. I haven't heard of kestrels flying through fences but many years ago I heard a radio programme where someone had seen a goshawk hunting by flying through a stock fence. Dave Kestrels are amazing little raptors Dave my only regret is I wish I had done a study on them much early in my life, I think I overlooked them before because they were a common sight and like most people all I had ever saw them do was still hunt or hovering over the fields. Not exactly a bird to produce excitement I thought but how wrong can one be, their piracy antics during the winter of 2012 is something I will never ever forget, neither will the short eared owl I suspect. Alan.
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Post by dogghound on Aug 29, 2015 15:11:41 GMT
Sorry Alan but it's clearly a juvenile male :-).
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Post by accipiter on Aug 29, 2015 16:27:31 GMT
Sorry Alan but it's clearly a juvenile male :-). That would be your prerogative to disagree of course Dan but in doing so you will be disagreeing with some of the top experts in this field, in my case one prefers not to bother as personally I see it as of “no real importance or interest as I may have mentioned previously.” But you may like to read again the information I provided, I have read up extensively on this subject and nothing I have read as changed my mind to the conclusion I came to in my first post. www.tandfonline.com/doi/pdf/10.1080/03078698.1980.9673764 If you have any difficulty with this link you could type in the address I provided in my previous post. Ps One does not think this is “clearly a male” or else all the literature by the experts on this matter would not state it is “very difficult indeed” to sex juvenile kestrels unless one has a " very clear view." Alan
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Post by dogghound on Aug 31, 2015 7:29:15 GMT
Sorry Allan but I have ringed hundreds of kestrels, I'm not arrogant enough to claim to be an expert but I know how to age birds :-). As I explained before, it's got the combination of juvenile feathering and a grey rump so fairly straightforward really.
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Post by accipiter on Aug 31, 2015 10:10:25 GMT
Sorry Allan but I have ringed hundreds of kestrels, I'm not arrogant enough to claim to be an expert but I know how to age birds :-). As I explained before, it's got the combination of juvenile feathering and a grey rump so fairly straightforward really. I thought we were discussing sexing and not ageing Dan and now you are speaking of examining one in the hand which is not available to most birders one would expect and entirely different from looking at a poor photograph too. I have looked again at this photo and I still cannot see a clearly defined grey rump not helped by the fact that this photo was taken in profile but all the same all the experts agree that sexing would still not be 100% accurate as one mentioned previously. But I do agree that this is indeed a juvenile kestrel as confirmed in my previous post. In the meantime I have also discussed this particular point to one or two very good knowledgeable falconers who also agreed it is “not possible to sex juvenile kestrels” to the degree of 100% unless the criteria is applied that I spoke about in my first post e.g. Their moult later in their first winter specifically the tail and upper tail coverts / rump . It is possible to sex 50% of very young kestrels but as I stated previously the rest do not follow the usual tail pattern e. g. grey for males and brown barred for female birds, so this too is still not a 100% reliable method as confirmed in the link one as already provided. Below is the summary of the paper with the important paragraph highlighted, just in case some members experienced difficulties with the link. Moult, Ageing and Sexing of Kestrels by Andrew Village DISCUSSION
In view of the above discrepancies, it would seem impossible to sex juveniles accurately on the colour of the head, rump, upper tail coverts or tail. Our results suggest that although these feathers are rarely grey in females, they are entirely brown in a number of males. This would lead to an apparent preponderance of females if juveniles were sexed solely on plumage colour. Cave (1968) calculated a sex ratio of 63% females at fledging among 912 nestlings sexed on the colour of their tails. Using our data in Table II for tail colour, an equal number of male and female juveniles would contain 42% brown-tailed males and 89% brown-tailed females, i.e. an overall ratio of 66% brown-tailed ("female") birds. The similarity of this figure to Cave's strongly implies that the unequal sex ratio reported was entirely due to the erroneous sexing of juveniles. Some individuals could be sexed in juvenile plumage: for example, those with either (a) grey heads or (b) grey rump, upper tail coverts and tail were invariably males in our sample. Similarly, no males had wing lengths larger than 260 mm and no females were smaller than 240 mm. Distributions of wing length for juvenile Kestrels divided according to the colour of the tail or upper tail coverts. However, these methods applied to a small percentage of juveniles, and most could be accurately sexed only by using the adult feathers that gradually appeared in the plumage during the first winter.
Anyway to change the subject slightly I am normally only really interested in a bird’s daily behaviour throughout the seasons but nevertheless one has enjoyed this discussion but I do not think I will be turning my interest to sexing juvenile kestrels any time soon! Ps I hope you do not you do not think I was implying you were arrogant Dan, on the contrary in fact one holds you in the very highest of esteem. All the very best Alan
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Post by dogghound on Sept 1, 2015 12:21:43 GMT
It's got a grey rump and it's a juvenile! Which means it's a male, aging can have everything to do with sexing in some species and visa versa. Females don't show grey rumps until they are mature, and even then many don't even show them when they are mature. You can see very clearly on the second photo where the bird is flying from the fence post that it has got adult male feathering moulting through. The rump is usually the first area to be moulted in this species. So mixed with the other juvenile feathers it's rather straightforward. I really don't understand why you are trying to complicate this with reams of information when the evidence is in the photo. It doesn't matter if you handle them or not, you can age and sex lots of species in the field with close views, good optics or both.
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Post by accipiter on Sept 1, 2015 14:01:12 GMT
Then what I "do not understand" is why all the experts evidence I have provided does not agree with you, having one in the hand “must presents a better prospect than trying to sex one in the field” I suspect, or trying to sex one by a posted photograph besides as I may have mentioned before I am very happy to identify the fact that I have just seen an adult male/ female or juvenile and suspect that most birders would too, although I am very happy to be proved wrong on "that point."
Nevertheless one hopes that the information I gave has been of some interest and provided some food for thought on this particular topic.
Alan
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Post by dogghound on Sept 2, 2015 6:52:50 GMT
Possibly because in a lot of cases you can't sex juveniles, you certainly can't sex them until they have begun to moult. However as this one has started to moult it can be sexed. A fresh juvenile in full juvenile plumage (unlike the bird in the photo) as you slightly say would be difficult/impossible to sex in the field.
Quoted from the paper you have provided.
"Adult Plumage. Males more than a year old were easily distinguished by their dove- grey tail, rump and upper tail coverts...."
As the bird in the photo is in the transitional stage between juvenile and adult feathering and is starting to show the above quoted features you can sex it and age it.
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Post by accipiter on Sept 4, 2015 18:28:47 GMT
Hi Dan this is what Michael Shrubb says on the subject – it is rarely possible to age or sex young kestrels in the field unless by size, although in their first winter they can usually be readily separated from adults by their bright fresh and unworn plumage. Dijkstre et al 1990, however in the Netherlands nestlings once feathered could be reliably sexed on plumage, males having greyish upper tail coverts with narrow pointed cross bars. Cave 1968 working in the same area found a similar pattern. It is not clear how universal this is, as Village et al 1980-. Dr Andrew Village) in a similar study noted that almost 20% of those nestlings ringed in Britain which later proved to be males had solid brown upper tail coverts . Although these accounts seem contradictory, the tail pattern and colouring is a very variable feature in kestrel populations and such variations are a marked racial characteristic of some. These discrepancies may therefore reflect genuine geographic differences.
And this is Gordon Riddle’s take on the subject on sexing and ageing.
Aging and sexing young kestrels is not an “exact science” as although they can be aged approximately by using wing length, this parameter cannot be used to sex them. The measurements of males and females overlap considerably. However the colour pattern of the upper tail coverts can be used to sex individuals if the chicks are three weeks or older and have wing lengths greater than 138 mm. Females have brown upper tail coverts with broad dark bands. This is however is “not totally fool proof.”
As the sexing of juvenile kestrels remains ambiguous I personally prefer not to bother to try to sex them as I like to only deal in 100% reliable facts whenever possible, also for the reasons one has already given.
Ps I have looked at the second photo again and agree there does seem to a grey tail but given all one has read so far by the experts there still remains an element of doubt in mind.
Alan.
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Post by dogghound on Sept 7, 2015 6:20:02 GMT
Well that's your call Allan, I don't fully think your understanding what I am saying. The literature you are quoting is referring to birds in full juvenile plumage which have not begun to moult and or birds which have darker/browner rumps after starting to moult (which can occasionally occur in small numbers of males). However in this case the evidence is quite clear to see in the photo.
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Post by accipiter on Sept 7, 2015 20:20:36 GMT
Thank you Dan for answering.
Alan
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