Unfortunately Nick (what is it they say about assumption ) neither body mass nor condition has any noticeable significance for overwinterers against fresh migrants.
Species like Chiffchaff and Blackcap in this instance undergo a partial winter moult and a complete summer moult, so birds from either would have identical plumage in spring. The effects of their spring migration has little if any perceivable bearing (through wear and abrasion) on their appearance once they finally arrive here.
As for body mass, you're right in that it's unperceivable to the human eye for a intents and purposes. Don't forget that your plump Blackcap (undoubtably heavier in weight due to your fat balls than those fresh in spring migrants) is likely to still appear plumper due to the effect of her trying to insulate herself with air in amongst her feathers against our cold winter. Whilst fresh spring birds may perhaps be slightly lighter in weight it's not perceivable in the field and many (most?) stop off to gorge themselves on route so arrive at a healthy weight anyway. I've seen many autumnal eastern vagrants in the UK (which have travelled thousands of miles) which appeared healthy enough and certainly had no external signs of malnutrition yet when caught were quite severely underweight and by the same token, retraps have highlighted the speed with which they can, under the right conditions etc, put that weight back on.
As for their song, it's unfortunately all supposition on our behalf. Sonograms may be a way forward but then how do we seperate those winterers and new arrivals in the first place? Back to square one
An interesting subject. Certainly not the last word on it. Let's see what spring and observations bring
Nick Hilton said
Fri Mar 11 10:17 PM, 2011
Typical - just been on Birdguides and Sand Martin recorded at Chelford (Cheshire) today !!!!!! (over a water near you tomorrow !!!!)
Nick Hilton said
Fri Mar 11 10:15 PM, 2011
How about body mass and condition ?
Difficult I know but I have noticed the female Blackcap that has frequented my garden over the last month or so is particuly plump and in fine condition (presumably from all the fat balls she's been tucking into). Would it not be a sensible assumption that a bird that had travelled 1500 miles would not be in top condition and comparitively lighter (I appreciate trying to judge body mass in the field would be somewhat difficult but general "condition" should be judgeable !!)
From doing years of visiting the same spot on a weekly basis my records note that early in the season migrants songs tend to be quite half-hearted, just a few bars, as though they were practising and not too sure !! Potentially migrants in full song early in the season could be over-wintering birds (on the basis they have been "practising" earlier !!!)
A minefield, I know, but an interesting subject ! (hopefully the first will be Sand Martin and then this debate will be obsolete !!!!!!!!!!!!!!!)
Ian McKerchar said
Fri Mar 11 9:56 PM, 2011
And if you could Henry I'd be really interested to know! Personally and from experience with known overwinterers, I really couldn't begin to seperate them from true fresh spring migrants on song (not to mention plumage!)
Henry Cook said
Fri Mar 11 8:47 PM, 2011
Tough question Ian! From my experience in Cornwall, overwintering Chiffchaffs and Blackcaps often sing throughout the winter which makes it even tougher to detect fresh migrants down there. What I suspect are the true migrants sing with more gusto when they arrive, however this is speculation as I can't confidently tell wintering and long-distance migrants apart on plumage.
Ian McKerchar said
Fri Mar 11 8:39 PM, 2011
But is your first spring Chiffchaff a true migrant or an overwinterer having an early blast like they do Peter
Pete Astles said
Fri Mar 11 8:36 PM, 2011
Chiff Chaff is the top one for me. The first one I hear always cheers me up a quintessential sound of spring. I know there are more glamorous birds but the first Chiffy and the first Cuckoo always do it for me. By the way old Cheshire custom the first Cuckoo you hear take your shoe off it brings good luck for the rest of the year. You look a divi but so what ? think of all that luck coming your way !!
Ian Campbell said
Fri Mar 11 4:40 PM, 2011
The first Wheatear passed through Portland Bill Observatory on Tuesday of this week. Cheers Ian
Ian McKerchar said
Thu Mar 10 9:30 PM, 2011
And therefore Chiffchaffs don't count
Or Blackcaps
-- Edited by Ian McKerchar on Thursday 10th of March 2011 09:31:09 PM
Joey Eccles said
Thu Mar 10 9:14 PM, 2011
The south?
Henry Cook said
Thu Mar 10 8:19 PM, 2011
Let's see where in GM gets the first proper summer migrant! Any bets?
Ian McKerchar said
Thu Mar 10 8:10 PM, 2011
Tony Coatsworth wrote:
From Birdguides today - keep those eyes to the skies
Won't necessarily see many Wheatears if you do...
Tony Coatsworth said
Thu Mar 10 7:05 PM, 2011
From Birdguides today - keep those eyes to the skies
14:50 10/03/11 Sand Martin Suffolk Thorington Street
12:30 10/03/11 Northern Wheatear Guernsey Pulias Headland
Also a load of Frogspawn appeared in my pond
Species like Chiffchaff and Blackcap in this instance undergo a partial winter moult and a complete summer moult, so birds from either would have identical plumage in spring. The effects of their spring migration has little if any perceivable bearing (through wear and abrasion) on their appearance once they finally arrive here.
As for body mass, you're right in that it's unperceivable to the human eye for a intents and purposes. Don't forget that your plump Blackcap (undoubtably heavier in weight due to your fat balls than those fresh in spring migrants) is likely to still appear plumper due to the effect of her trying to insulate herself with air in amongst her feathers against our cold winter. Whilst fresh spring birds may perhaps be slightly lighter in weight it's not perceivable in the field and many (most?) stop off to gorge themselves on route so arrive at a healthy weight anyway. I've seen many autumnal eastern vagrants in the UK (which have travelled thousands of miles) which appeared healthy enough and certainly had no external signs of malnutrition yet when caught were quite severely underweight and by the same token, retraps have highlighted the speed with which they can, under the right conditions etc, put that weight back on.
As for their song, it's unfortunately all supposition on our behalf. Sonograms may be a way forward but then how do we seperate those winterers and new arrivals in the first place? Back to square one
An interesting subject. Certainly not the last word on it. Let's see what spring and observations bring
Difficult I know but I have noticed the female Blackcap that has frequented my garden over the last month or so is particuly plump and in fine condition (presumably from all the fat balls she's been tucking into). Would it not be a sensible assumption that a bird that had travelled 1500 miles would not be in top condition and comparitively lighter (I appreciate trying to judge body mass in the field would be somewhat difficult but general "condition" should be judgeable !!)
From doing years of visiting the same spot on a weekly basis my records note that early in the season migrants songs tend to be quite half-hearted, just a few bars, as though they were practising and not too sure !! Potentially migrants in full song early in the season could be over-wintering birds (on the basis they have been "practising" earlier !!!)
A minefield, I know, but an interesting subject ! (hopefully the first will be Sand Martin and then this debate will be obsolete !!!!!!!!!!!!!!!)
From my experience in Cornwall, overwintering Chiffchaffs and Blackcaps often sing throughout the winter which makes it even tougher to detect fresh migrants down there. What I suspect are the true migrants sing with more gusto when they arrive, however this is speculation as I can't confidently tell wintering and long-distance migrants apart on plumage.
Cheers Ian
Or Blackcaps
-- Edited by Ian McKerchar on Thursday 10th of March 2011 09:31:09 PM
Won't necessarily see many Wheatears if you do...