What about the passenger pigeon.

Well over several millions I think, but honnestly I don't now much about that.

The question raises that of when do a colony start and end?

Best to you ANders.

ED

To my knowledge Red-billed quelea bird found in Africa lives and breeds in huge flocks.

I agree with Etienne Sir but Passenger pigeons are extinct now.

Dear Etienne and Arvind, 

Thank you very much. I had already listed these species, but also made a list of ten other species that and been observed in numbers exceeding 100,000. Actually, I was more interested in your 'personal' observations. 

All the best wishes, 

Anders

Hi Anders. Below the abstract of an our little work on heronries in China - Perhaps, should be of some use

Waterbirds 27(Mar 2004):126-128 ·

We counted the heronries at two study areas in China, where important but unknown numbers breed. At Poyang Lake, within a 1,800 km2 area, we found ten heronries with Little Egret (Egretta garzetta), Intermediate Egret (Egretta intermedia), Great White Egret (Ardea alba), Cattle Egret (Bubulcus ibis), Chinese Pond Heron (Ardeola bacchus), and Black-crowned Night Heron (Nycticorax nycticorax), and at Tai Lake we found five heronries within a 4000 km2 area. Heronry size ranged from a few hundred nests to 36,400 nests. Several heronries were located within human settlements, in contrast with the sites used in Europe and in North America, where herons tend to avoid human disturbance. An extrapolation of the mean densities observed at the two study areas, for all the zones of mainland China that are cultivated mostly with rice, provide a first estimate of a total numbers of up to some five million nests of herons and egrets, which is much higher than previously suggested for China.

All the best

Paolo

Dear Paolo, 

Great example, thank you so much. 

All the best, 

Anders

Dear Anders,

years before we reviewed all the group/colony size measures of those bird and mammal species that had group size distributions (raw data) in the literature available for us. That paper comes with a Table containing maximal values as well. We had only cca 15 bird species, none had maximal values at 100,000 or higher. Since you consider food limitation, thus body size should also be considered, I mention that we had a maximum value of 14,900 pairs for the American White Pelicane -- a very large-bodied bird.

Find the paper here: 

https://www.researchgate.net/publication/237385831_Measures_of_sociality_two_different_views_of_group_size

With all the best wishes,

Lajos

Article Measures of sociality: two different views of group size

Mr Moller,

In the electronic plataform eBird you can find some information for this.

In Chile, we had recorded huge numbers in one locality of :

Please provide information on species name, date, year, locality, coordinates.

Franklin's gull (32.000), 15-02-2011, "Rocuant - El Morro", -36.7354449 S -73.0929422 E. Recorded by Fabrice Schmitt.

Sooty shearwater (100.000), 12-02-2014, "Beach Huape", -39.9182616 S -73.5322022 E. Recorded by Heraldo Norambuena

Magellanic penguins (130.000), 01-12-2013, "Isla Magdalena", -52.920555 S, -70.5597 E. Recorded by Santiago Imberti.

My best wishes

Fernando

Dear Lajos and Fernando, 

Thank you very much for your help. 

All the best wishes, 

Anders

Apparently, about a million Amur Falcons congregate in Nagaland, India during passage - sometimes termed as the largest single species raptor congregation in the world.

http://www.birdlife.org/asia/news/action-amur-falcons-brings-hope-end-hunting-nagaland

Dear Abhishek Raj, 

Thank you for your reply. 

Yours sincerely, 

Anders Pape Møller

Dickcissels (Spiza americana) form large feeding aggregations and can rapidly exploit locally abundant food sources, including commercially grown cereal grains.  On their wintering grounds in South America, individual roost sizes of Dickcissels could reach up to three million birds.    

See the following publications:

Basili, G. D., and S. A. Temple.  1999.  Dickcissels and crop damage in Venezuela: defining the problem with ecological models.  Ecological Applications 9:732-739.

Basili, G. D., and S. A. Temple. 1999. Demographic characteristics of Dickcissels in winter. Studies in Avian Biology 19:281-288.

Basili, G. D., and S. A. Temple. 1999.  Winter Ecology, behavior, and conservation needs of Dickcissels in Venezuela.  Studies in Avian Biology 19:289-299.

Basili, G. D. 1997. Continental-scale ecology and conservation of Dickcissels. PhD Dissertation, University of Wisconsin, Madison, Wisconsin, USA.

ffrench, R. P.  1967.  The Dickcissel on its wintering grounds in Trinidad.  Living Bird 6:123-140.

Dear Lawrence, 

Thank you so much. I will check the references that you kindly proposed. 

Yours sincerely, 

Anders Pape Møller

Plenty of useful bird data is available at ebird:

http://ebird.org/ebird/eBirdReports?cmd=Start

Kind regards,

Holger Woyt

Dear Holger, 

Thank you very much. I already checked bird. 

All the best wishes, 

Anders

Bramblings (Fringilla montifringlilla) have been reported to aggregate during winter in large flocks occasionally.

There is a report on "Surfbirds" on 2-4 million individuals in Austria, Lödersdorf  on 17 Jan 2009 (there is a footage on YouTube as well). Another large aggregation was reported in northern Slovenia sometimes in 2005. I only saw pictures of the Slovenian one (I never had the chance to go and see it) and it was really impressing. A similarly large flock was reported in the Hungarian literature sometimes around 1802 (I have to check for a more exact date; I read it in a nice book that collected all recorded unusual phenomena of weather and nature in Hungary).

Kind regards,

Gábor Magyar

Dear Gábor Magyar, 

Thank you so much for your help. 

All the best wishes, 

Anders 

It may not be the largest bird flock ever reported but in terms of its relative size compared to the world population the wintering habits of the Spectacled Eider (Somateria fischeri) is notable, since it seems to winter in a huge concentration in the Bering sea south of St Lawrence Island in large single-species flocks of 10 000 individuals or more (cf. "At-Sea Distribution of Spectacled Eiders: A 120-Year-Old Mystery Resolved by Margaret R. Petersen, William W. Larned and David C. Douglas, The Auk Vol. 116, No. 4 (Oct., 1999), pp. 1009--1020). The estimated world population of the species is 330,000-390,000 individuals and 333,000 individuals were estimated to winter in the indicated area.

Gábor Magyar

The highest count reported on ebird for Australia were 3,000,000 Short-tailed Shearwater Ardenna tenuirostris in Tasmania in January this year.

http://ebird.org/ebird/australia/sightings?listType=high_count&locInfo.regionType=country&locInfo.regionCode=AU&beginYear=1900&endYear=2016&continuous=true&sortBy=how_many&o=desc

Are you considering historical accounts of species such as the passenger pigeon? Also, there may be some information describing the large mermerations of red-winged blackbirds in the early 1900s. 

Heather

When I was in the Platte River Valley in Nebraska a few springs ago, I was floored by the flocks of Snow Geese. The flocks of Sandhill Cranes were impressive as well. Both were in flocks numbering the tens of thousands.

In Yakima, Washington, (46.64307, -120.58254) there is a known wintering roost congregation of American Robins (Turdus migratorius) that is estimated to contain well over 150,000 birds.  I've been involved with trying to estimate numbers of this known roost site for a few years and we routinely count over a 4 evening period close to 80,000 birds entering the roost area.  There are many more birds that undoubtedly go uncounted.  It is an impressive spectacle to see so many robins entering one small area to roost every evening during winter.

Dear Colleagues,

Thank you kindly for your help and references.

Yours sincerely,

Anders Pape Møller  

favorite bird flock photo:

http://www.dailymail.co.uk/news/article-2108788/Flock-awe-Even-elephants-scared-jumbo-cloud-tiny-red-billed-birds.html

Most of the worlds flyways have semi-regular large flocking events:

Eilat

http://ibrceilat.blogspot.com/2015/05/the-best-ever-raptor-day-count-in-eilat.html

https://www.hawkmountain.org/science/veracruz-mexico/page.aspx?id=3578

http://insider.si.edu/2014/11/panama-shatters-raptor-migration-record/

Australia: 2 million Oriental Pratincole on a beach

http://www.awsg.org.au/stilt/Stilt-57.pdf

250,000 shorebirds in Laguna Ojo de Liebr

http://www.calwater.ca.gov/Admin_Record/C-056771.pdf

Dear Robert Scott Clemens, 

Thank you very much for your reply. 

Yours sincerely, 

Anders Pape Møller

Here some recent information: 

One of the world’s biggest colonies of penguins is at risk from a volcano that has erupted on their small sub-Antarctic island in a British overseas territory.

British scientists fear that Mt Curry’s eruption could have a serious impact on the 1.2m chinstrap penguins and nearly 200,000 macaroni penguins based on Zavodovski, one of the South Sandwich islands.

The colony of chinstraps is the largest of the species in the world, but there are now fears over their fate due to the ash and smoke drifting from the volcano. It erupted in March and is still spewing columns of smoke that have been captured by satellite images and fishermen.

The island is so remote that experts at the British Antarctic Survey (BAS) say it will be impossible to assess what impact the eruption has had until an expedition visits in December 2016 or January 2017, but the risk to the penguins is that at worst they could be buried alive in ash, burned or suffer breathing difficulties.

The danger to the 55cm tall chinstraps comes from the fact the eruption began during their moulting season. During this time, which can last six weeks from the first to the last bird in the colony, the penguins are not waterproof and cannot go into the water.

“They can’t escape. We don’t really know how bad things are on the island, it may be that they’re fine, it may be that they’re not. But there is a concern,” said Mike Dunn, seabird ecologist at BAS. “Had they not been moulting at the time, there would be no issue at all, because the penguins would simply swim off.”

This article was published by The Guardian on 06 Jul 2016.

At the end of the sixties, roots comprising several millions of bramblings were known in the French Pyrénées. In December 1967, a roost in the Pyrénées-Atlantiques comprised around 20 million birds (Héméry and Letoquin 1976, http://documents.irevues.inist.fr/bitstream/handle/2042/58486/LATERREETLAVIE_1976_1_52.pdf?sequence=1.

Thank you kindly for your help,  Anders

http://ebird.org/ebird/view/checklist/S18808991

Thank you very much. 

Yours sincerely, 

Anders Pape Møller

A wintering roosting places close to Setubal (Portugal) of more than 2.6 millions of Woodpigeons (Columba palumbus) at 5 December 2003