I agree with Colin Smale (LBC Bird Sightings 30 April...'Red Rump gone') that saying about a particular bird, "it's gone", can be a very tricky report to make with certainty,........ especially when the bird reappears later in the day to one's own embarrassment and to the chagrin of those birders who cancelled their trip/twitch.
I also posted yesterday at much the same time as Colin - 1.16 and 1.15pm respectively - re the disappeared Red-rumped Swallow. At least it had disappeared from the immediate Far Ings area (with people looking for the bird from about dawn to nearly midday without success), but at the back of my mind I couldn't help wondering if it had just moved to somewhere not too far away,eg. to the other (Lincs) side of the Humber Bridge.
The problem for a birder going for a bird, can be compounded by the fact that one may want to get to see a bird before it, perhaps, clears off unexpectedly.....the "Oh! you should have been here 5 minutes ago" syndrome. In that case, especially if a long car journey is involved, one HAS to leave home early, before the first Yes/No reports are put out.
With a reservoir, there's no real problem, eg. re the Bufflehead at Covenham this past weekend : either the bird is on the reservoir or it isn't...."it's gone". With a distinctive large bird, such as the Red-legged Stint at present at Frampton Marsh RSPB, sooner or later "it's gone" will be fairly definite. However, even some large birds can "go" and reappear a few days later, eg. the White Stork and the Great-white Egret at Kirkby-on-Bain earlier in the year (ie. moving around a large area, much of it not covered by birders).
Certain birds are notorious for appearing and disappearing during their stay in an area. One which immediately springs to mind is the Great Grey Shrike. They often roam over such a large area that they can lead birders a very merry dance : hence the advice, " If you've got something better to do that you like, never twitch a Great Grey Shrike ".
Some birds have recently been reported as "gone" but in fact were just lying low for a few hours, eg. the Ring Ouzel at Woodhall Spa.
Indeed, reporting a bird has "gone" can be a very tricky matter and specific knowledge of a particular species' habits can sometimes be most important in coming to a (hopefully) correct decision....
....and sometimes basic common sense can be the answer.
Freddy
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