I reckon it's the same at every birding site in the county John. Most of us have our local patches and finally when something of rarity value turns up most of us like to go off and see it. The knock-on finding of good birds at a site with other good birds present is famously known as the Patagonia Picnic Table Effect or in Manchester's case from now on, the Hollingworth Car Park effect!
I guess it's obvious that more birders will produce more coverage and hence discover more birds and I'd never heard of it being called the Patagonian Picnic Table Effect before. (Just Googled that. There is a single picnic table south of the small township of Patagonia, Arizona. Birders once found a rarity there, this drew in other birders who found a second rarity. Now it's enshrined in folk law and no birder would pass by without stopping to look. Hence even more discoveries).
But my question wasn't about how birders find birds but how vagrants find each other - and specifically these GN Divers.
Many instances of rarities finding each other must be down one vocalising and drawing in another but unlikely(?) for divers. I agree with Ian that loads of rare/scarce birds are overflying, or landing in, GM but remain undiscovered (e.g. Frigatebird perhaps?) so there could well be 3 (or more) GN Divers scattered around little watched reservoirs in the hills.
I reckon it's the same at every birding site in the county John. Most of us have our local patches and finally when something of rarity value turns up most of us like to go off and see it. The knock-on finding of good birds at a site with other good birds present is famously known as the Patagonia Picnic Table Effect or in Manchester's case from now on, the Hollingworth Car Park effect!
I go along with the more twitchers/birders more birds.somewere like hollingworth has its few regulars,then after the first diver was found there are suddenly 30+ visitors a day to hollingworth,and this leads to more birds being seen.not in this case as i think it was one of the regular watchers who found both,but it happens all over. At penny there are many instances where a decent bird turns up and then from the regular 5 or 6 who get on when they can,a hoard of twitchers turn up then suddenly something else is found,its quite often the sheer numbers of birders grilling a site that finds that extra bird. And in truth who will go to hollingworth once the diver has gone,back to the 2 or 3 regulars,so until they stumble on something rare,the place is under watched,just like penny,how many do the full circuit,or go to the west end regular.hardly any apart from a couple of us,then when a slav grebe is found at the west end,we have every man and his dog at that end,for 2 days then back to normal no one,but there could be a night heron or two at that end for months and no one would know,until it flew past horrocks hide on its way off,it would be deemed as a fly through.
-- Edited by JOHN TYMON on Saturday 28th of November 2009 08:05:21 AM
Interesting this; Is it possible that certain species of birds just follow the same 'map' when flying over land. All migrating birds are born with or learn the route that they must follow. Juvenile birds do seem to wander about so the GNDivers at Hollingworth lake may just have taken the same route and seen the lake as they passed over.
As we're specifically talking about vagrants here Dave (county and national), then by and large that'll be a no from me
Interesting this; Is it possible that certain species of birds just follow the same 'map' when flying over land. All migrating birds are born with or learn the route that they must follow. Juvenile birds do seem to wander about so the GNDivers at Hollingworth lake may just have taken the same route and seen the lake as they passed over.
Years ago when I was in a Cessna for the first time flying out of Barton airport I was asking about navigation and the pilot just said follow the train tracks below. In the distance there were 3 other planes following exactly the same train tracks.
- A fascinating topic this, which brings to mind the mid/late winter of 2002. On 25th January, It was very cold and I was birding alone around Marsden lake, Low Barns (a small Durham Wildlife Trust reserve). The lake was largely frozen over, but out of only 5/6 Aythya ducks lolling about on the ice by an open patch of water, I picked out a female Ring-necked Duck; a site "tick" for me. This individual hung around into April, when another visiting birder noticed it had been joined by a drake. After some days I called in to see both birds and was enjoying watching the drake actively feeding/diving when it popped up within seconds an impossible distance from where it had submerged; there was a second drake! There were three Ring-necked Ducks therefore for a brief week or so, making Low Barns temporarily the "Ring-necked Duck UK capital." I pondered on whether or not the presence of the female had somehow "drawn in" the males; and still have no real answer. It may well be that many more vagrants than we ever see are generally wafting about in greater numbers than we suspect, and they vocally or visually actively seek company. Another contributory explanation may be that birds are brilliant at finding suitable habitat to their liking, especially when "lost" and selection would confer survival value to such an attribute. In support of the "ideal habitat" argument, I did find another drake Ring-neck Duck here on 28th February 2007, so Marsden Lake would appear to be simply to their liking.
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Has anyone considered that this might be a third Great Northern Diver at Hollingworth? I'm sure I remember someone posting last week that a Diver had flown off high to the West, would it really be likely to come back?
there's little doubt it would have turned back once it saw the smog over Wigan
I don't doubt for one minute that vagrants find each other by call, much as we would shouting to a mate in the crowd at a football match or similar. But that they find each other at the same location in the first place, often amongst thousands of other species must surely be due to chance and perhaps the fact that they're slightly more regular than we give them credit for. For every one White-rumped Sandpiper that's found how many do we think go unnoticed? Does the extra attention that one find brings mean the discovery of further individuals by birders? In the main the latter is certainly true, how often has a the arrival of hoards of twitchers brought the discovery of further vagrants? Very often is the answer.
Certain birds,Waxwings are a good example must find one another by call(Waxwings are VERY vocal birds),quite likely this happens with waders as well.A lot of waders call frequently in flight and this surely must enable them to find birds of the same species.However how GNDs fit into this i'm not sure,either they must have flight calls,or it could just be purely co-incidence that they end up on the same water?
How many times do a small group of Dotterel or Waxwing turn up somewhere and then are joined by others. Even vagrants do, a few years back a White-rumped Sandpiper turned up on the east coast of Suffolk at Breydon Water. Then it was joined by another, then another and then another until all four birds were present together. Even on the west coast that would be an amazing coincidence, but for four western vagrants to find each other on the east is astonishing!!
Like Ian said it may just be chance or like us, when we go on our holiday we all look for the same thing, nice resort, sun loungers, pool etc. It may be the same for birds, they look for suitable habitat be it big fish-filled reservoir or an area with lots of berry bushes and just happen to bump into old friends. Either that or they all have pagers!
Has anyone considered that this might be a third Great Northern Diver at Hollingworth? I'm sure I remember someone posting last week that a Diver had flown off high to the West, would it really be likely to come back?
There are a few similar examples on the systematic list on the website. Most notably Great Northern Diver, Red-throated Diver, Long-tailed Duck and of course Pectoral Sandpiper.
Personally, I believe in chance and that these birds are over flying more often than we give them credit for. Perhaps the initial current Hollingworth GNDiver has been up all night calling for attention which attracted the new over flying juv? Simon could test that theory with few nights spent camping lakeside.
There are many similar examples throughout the UK. Perhaps there's more too it? If you relate it to the movements of people though then the chance theory has a, well, chance! One October whilst birding a tiny Cornish Valley I happened to bump into an old mate who I hadn't seen in years and now resided in Conneticut, USA. How many times have you gone on holiday abroad yet bumped into a friend or atleast someone you know from back home or from close to where you live?
In the immortal words of John Lennon 'give chance a chance'. Well, it was probably something about peace actually but I know what he was getting at.
Today there were 2 Great Northern Divers on Hollinworth Lake with a second bird joining the long stayer. How did they do that? They are not particularly vocal so I doubt the 2nd bird just happening to be overflying Hollinworth and was then attracted down by calls. Alternatively the birds could have recognised each other either by sight but I'm not sure that applies in this case either. My personal favourite is that the first bird has commuted to a nearby water where the second bird was already present and then returned to Hollinworth bringing the second bird with it. Well, it's a theory
I seem to recall there are many strange cases of one rarity attracting others 'out of the blue' Can anyone help me out with some examples?
at that end for months and no one would know,until it flew past horrocks hide on its way off,it would be deemed as a fly through.
Certain birds,Waxwings are a good example must find one another by call(Waxwings are VERY vocal birds),quite likely this happens with waders as well.A lot of waders call frequently in flight and this surely must enable them to find birds of the same species.However how GNDs fit into this i'm not sure,either they must have flight calls,or it could just be purely co-incidence that they end up on the same water?