The crowd of self-styled “twitchers” was hoping to catch sight of the Siberian accentor, brought to the UK on unseasonal easterly winds.
The bird had made one appearance on the Shetland Isles last week, but was later spotted in a car park behind the gas terminal in Easington, on the Holderness coast.
By dawn today, 400 spotters had arrived at the site, east of Hull and north of Spurn Point. By breakfast, their numbers had swelled to 900, waiting patiently to be led to a fence overlooking the site, where they could get a better view.
Among them was Keith Holland, 49, who had left his home in Bexleyheath, South London, at 4am, after seeing an alert on a bird watchers’ forum.
Mr Holland, an analyst in a scientific laboratory, said: “Some birds could be a once in a lifetime opportunity. I had to get there and, for me, personally, this is definitely up there as one of the top ten birds I’ve seen.
“I’ve had some great views and shots of the bird - I’ve been about 20 feet away.”
RSPB volunteer Tim Jones, 25, who helped marshall the spotters, said: “This is a mega rare bird and it’s only the second time its been Britain and the first time on the British mainland.
“They are not meant to be here but the recent weather has blown them off course.”
The accentor is distant relative of the common British dunnock but is distinguished by its black and creamy facial markings. Its natural breeding ground is in northern Siberia on both sides of the Ural mountains.
Mr Jones said: “We have had people from all over, and we are expecting more to turn up as the news travels.
“Only around 150 people can look through the fence and see the bird at one time and we have been organising a queue system. People can see the bird for ten minutes, then go to the back of the queue and wait their turn again.”