Abstract
Sewage ponds with exposed sludge are known to be excellent feeding sites for waders during migration. They still exist in parts of the world but are disappearing in pace with introduction of modern methods which do not involve open exposure of the sludge. Here I report a five-year study from a Swedish plant with open sludge ponds in the 1950s when many similar ones were still active. I counted the waders with frequent visits from 18 April through 2 November, 1952–1956. Ninety-three percent of the dates had a visit in at least one of the years giving an almost complete combined coverage of migration. Nineteen species were recorded at least once. The total average annual number of bird-days was 2868 (5% in spring). Most abundant were the Ruff Calidris pugnax with 35% and Wood Sandpiper Tringa glareola with 32% of all bird days. Temminck’s Stint Calidris temminckii showed the highest spring proportion of bird-days, 30%.
Highlights
Sewage ponds with exposed sludge are known to be excellent feeding sites for waders during migration
In several countries there are a few publications about the birds of sewage treatment plants or sewage farms
The number of years with a visit on a specific date was: (16%) of the dates had a visit in all five years, (15%) in four, (20%) in three, (21%) in two, and 42 (21%) in one year
Summary
The earliest visit was on 22 April and the latest on 2 November, a period of 195 days. The number of years with a visit on a specific date was:. 13 (7%) days were not visited in any of the years. 47%, 64%, 58%, 43%, and 52% of the possible days each year. 514 visits were payed which is 53% of the total number of 975 possible days. Thanks to the fact that the visits were paid on different days in different years, as much as 93%. Of the dates had a count in at least one of the years. The site was surveyed on a variable number of days in each of the five years 1952–1956 Antal besök olika månader och år under perioden 22 april–2 november. Almost all counts were made by myself, but on a few days two friends of mine helped to make the count
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