Rare bird questions

[kas]

As I have only been birding a few years I havent yet got to the twitching stage. But I have taken alot of enjoyment reading about rare birds that turn up, especially the recent influx of American birds that have been blown :flyaway: in. But I have a few questions. :brains:

If a bird is blown over the Atlantic from America, does it stand any chance of getting back across the Atlantic to America?

If not what happens to it?

Have any British birds been blown over the Atlantic to America?

And finally what percentage of rare birds are actually discovered? :stuck:
(This question probably has the same answer as how long is a piece of string, but thought I'd ask it anyway

Many thanks kas :t:

[Crowquette]

I am just glad that the government officials haven't figured out yet how to require birds to have immigration visas! Lol With the Avian Flu situation looming worldwide though, I bet they are working on it. :( But all joking aside, I bet if a bird ends up blown across an ocean it finds a climate as close to what it knew at home and does its best to live out the remainder of its days as happily as possible.

Hugs,
Crowquette

[Jos Stratford]

Hi there,

a few answers to the best of my knowledge...

If a bird is blown over the Atlantic from America, does it stand any chance of getting back across the Atlantic to America?

Depends on the bird
- for the small passerines and simliar, the chance is very very remote. They are more likely, if they survive, to winter in Britain or southern Europe (several have been discovered in mid-winter in the UK - Baltimore Oriole, Golden-winged Warbler as examples), then presumably try to undertake a northerly migration this side of the Atlantic - most would be lost to the birdwatching public as they move into the great European land mass, but the Belted Kingfisher of the spring seems to have been an example of this

- for waders and some wildfowl, the chances are still low, but I'd say better. As breeders of the high latitudes, going far enough north from Europe and from America equals the same place, give or take a few large lumps of ice :). I think some waders are suspected to reorientate. Otherwise it's up and down in Europe year after year, as evidenced by regular East Coast records in August and occasional records in Finland etc.

Have any British birds been blown over the Atlantic to America?

Yes, certianly some of the waders and gulls, eg the likes of Redshank et al are 'regular'ish and I think some passerines have been too (but might be wrong there). Obviously prevailing winds favour westward movement of birds over the Atlantic, accounting for the far greater incidence over here.

And finally what percentage of rare birds are actually discovered?

Depends where they land - on Scilly in October, it's going to be 'most', on the Cornish headlands, it's going to be 'a lot of them', on the Irish west coast, 'some of them' and if in inland Britain, 'a percentage of them'! Also would depend on the type of bird - waders much more likely to be found than Nighthawks, ducks more likely than warblers, etc etc.


Hope that answers to a degree!

[delia todd]

As I have only been birding a few years I havent yet got to the twitching stage. But I have taken alot of enjoyment reading about rare birds that turn up, especially the recent influx of American birds that have been blown :flyaway: in. But I have a few questions. :brains:

If a bird is blown over the Atlantic from America, does it stand any chance of getting back across the Atlantic to America?

If not what happens to it?

Have any British birds been blown over the Atlantic to America?

And finally what percentage of rare birds are actually discovered? :stuck:
(This question probably has the same answer as how long is a piece of string, but thought I'd ask it anyway

Many thanks kas :t:

Kas - what interesting questions, I've had some of them half-formed in my mind for a while. Thank you for asking them.

D

ps Jos's post came in before mine - he's come up with the goods as usual. Thanks Jos.

D

[alcedo.atthis]

"If a bird is blown over the Atlantic from America, does it stand any chance of getting back across the Atlantic to America?"

Some birds (Canada Geese) actually fly to here, under their "own steam" and presumably make the return under their "own steam" unless like 6TU2 they are shot by visiting wildfowlers from over the pond, from whence the birds came, but that's another annoying story.

"If not what happens to it?"

Take the Wren. Originated across the pond, doing quite well here.
Are "all" White-headed Ducks in Europe introduced, or have man introduction ancestry. Who knows?

(Snipped) and answered by Jos


Regards

Malky

[Henry B]

Kas, I,m sorry I can not help with the bird questions,but I have solved the piece of string puzzle.....it,s 23.5" inches,hope this helps..

[alcedo.atthis]

"Kas, I,m sorry I can not help with the bird questions,but I have solved the piece of string puzzle.....it,s 23.5" inches,hope this helps.."


Ahh, but at what temperature??


Regards

Malky

[David FG]

"If a bird is blown over the Atlantic from America, does it stand any chance of getting back across the Atlantic to America?"

Some birds (Canada Geese) actually fly to here, under their "own steam" and presumably make the return under their "own steam" unless like 6TU2 they are shot by visiting wildfowlers from over the pond, from whence the birds came, but that's another annoying story.

"If not what happens to it?"

Take the Wren. Originated across the pond, doing quite well here.
Are "all" White-headed Ducks in Europe introduced, or have man introduction ancestry. Who knows?

(Snipped) and answered by Jos


Regards

Malky

As far as the Wren goes, is it not more likely that it came 'the other way' - ie from the Americas into Asia and spread from there?

[Bluetail]

And finally what percentage of rare birds are actually discovered?

Depends where they land - on Scilly in October, it's going to be 'most', on the Cornish headlands, it's going to be 'a lot of them', on the Irish west coast, 'some of them' and if in inland Britain, 'a percentage of them'! Also would depend on the type of bird - waders much more likely to be found than Nighthawks, ducks more likely than warblers, etc etc.Here's an old post from uk.rec.birdwatching, cribbed pretty much verbatim.

In the March '97 issue of British Birds there was a paper by Pete Fraser called "How many rarities are we missing?". Fraser analysed the BBRC statistics for 1958-92 and found that, despite steadily increasing observer coverage over the years, there wasn't much variation in the percentage of rarities found at weekends (44% in 1958, reducing to 40% in 1992). Sites well-watched by weekend visitors from the big connurbations showed the most weekend bias; those covered more exclusively by local observers the least.

He then devised a model that ran thus: Assuming that no site is covered with 100% daily efficiency, the rarities found on any given day will consist of (1) a percentage of that day's arrivals, (2) a percentage of the previous day's arrivals which were not discovered then and (3) a (small) number which arrived even earlier, also previously undetected. At well-watched sites he reckoned that 90% of all rarities were discovered, of which 40% were recorded only on one day. At less well-watched sites 70% were recorded on one day only, probably because with less coverage it is easier to lose track of the birds and because fewer are found on the day they arrive. He ended up with an estimate that 60% of rarities remain beyond one day; of these 70% are still present the next day, 70% of those the day after and so on.

Calculations were a question of first finding the best fit between the model and the statistics. In the Isles of Scilly the reduction in numbers of birds found on Monday pointed to an efficiency of 92% on Sundays and less effort on Saturdays (76%) than on weekdays (78%) - which seems logical since Saturday is the big change-over day there.

In 1990-94 the average number of rarities discovered each year was 755, while, at a conservative estimate about 800 were missed. The rate of discovery for passerines, near-passerines and waders was significantly less than for larger birds (unsurprisingly). For passerines, the percentage missed in different areas were:

Fair Isle 11%
Scilly/Cape Clear 11%
Orkney/Shetland 45%
South Coast 53%
East Coast 57%
Elsewhere 60%

What the author didn't cover was whether there are any differences between the different seasons - a pity since, on average, autumn birds stay longer than spring ones and winter ones longer still and I would have thought this would be reflected in variations in the finding efficiencies. (I might be wrong though; I'm no mathematician.)

Anyway, on Fraser's calculations (which I'm sure he wouldn't want taken too seriously) it seems that we're finding less than 50% of the rarities.

[Henry B]

"Kas, I,m sorry I can not help with the bird questions,but I have solved the piece of string puzzle.....it,s 23.5" inches,hope this helps.."


Ahh, but at what temperature??


Regards

Malky
It was taken straight out of my pocket,in the dark..data does not compute data does not compute.....

[alcedo.atthis]

"It was taken straight out of my pocket, in the dark.."


Yes, just like a few of the members.
"The lights are off, they ain't at home" (Variation)

Regards

Malky

[kas]

Thanks everybody, interesting reading. I find bird migration amazing and feel so sorry for the poor wee things that get lost, although I wouldnt complain if a few of them ended up in my patch.
I do believe Caithness is underwatched, so birds will easily pass through here unnoticed.The last 2 species I had heard pass through were Snowy Owl and Black Kite, so that proves the theory that the larger birds are spotted far more.
Orkney throws up quite a few birds each year and we are only about 7 miles across the water from here. I see it out my front window very clearly.
I have learnt alot from this thread :clap: Thankyou again.

And as far as the string question goes I couldnt get the answer as I am too young for imperial mesurements. We were taught metric. 3:-) Ha Ha only joking.