Seabird 2000
Herring Gull Larus
fuscus
The Herring Gull has a near Holarctic distribution, breeding
mainly in the middle and high latitudes. It is widely distributed
around the coasts of Britain and Ireland, and prefers to nest on
Rocky coastline, with cliffs, islets and offshore islands, though a
range of other habitats are used including sand dunes, shingle
banks and, increasingly, buildings in urban areas. A small
proportion of the population nests inland [1], mainly on lake
islands and moorland. The Herring Gull is an opportunist feeder,
being both predator and scavenger. While primarily a coastal
feeder, it readily avails of the often abundant food supplies
available indirectly from man, especially waste from the fishing
industry and landfill sites. Outside of the breeding season,
Herring Gulls are common along most of the coastline and inshore
waters of Britain and Ireland and also occur inland.
The Herring Gull population experienced a marked increase in
all parts of its west European range through much of the 20th
century and especially in the period from about the 1930s to at
least the 1970s. The main reasons for the rise in population are
considered to be increased protection, especially from egg
collecting and shooting, and the species ability to exploit new
food resources derived from the activities of man, notably discards
and waste from the fishing industry, refuse tips and sewage
outlets. In the last decades of the 20th century, however,
populations stabilised or even declined in parts of the range. In
Britain and Ireland, the population breeding on the coast almost
halved in numbers between Operation Seafarer (1969-70) and the SCR
Census (1985-88) (from 343,586 to 179,717 pairs). Since the late
1980s, the overall population in Britain and Ireland has continued
to decline though local increases have occurred, especially in
England.
Census Methods
During Seabird 2000, the recommended census unit for Herring
Gulls was the apparently occupied nest (AON). Counts of AONs were
conducted from either within the colony or from a suitable vantage
point. Large colonies were surveyed using sample quadrat counts of
AONs. At colonies that could not be accessed (e.g. on marshy ground
or on islands) and where there was no suitable vantage point, flush
counts of individuals attending the colony were made. Counts of
individuals were divided by two to provide a rough approximation of
the number of AONs present. This is the least accurate method for
censusing breeding gulls, as such counts will include an unknown
percentage of non-breeders and attendance at the colony by both
breeders in a pair is highly variable throughout the day and
throughout the breeding season. The accuracy of counts of
individuals is difficult to assess. However, during Seabird 2000,
only 4% of the population estimate for Britain and Ireland was
obtained from counts of individuals, compared to 6% during the SCR
Census (1985-88). Hence the estimates from the two censuses are
comparable in terms of the methods used. In mixed colonies, more
often than not shared with Lesser Black-backed Gulls, the
determination of the proportion of a count to assign to a
particular species provides a further potential source of error, as
the eggs of the two species can not be readily distinguished during
counts. In all but the smallest colonies, where individual nests
may be attributed to any given species, it was recommended that the
proportion of Herring Gulls be determined from sample head counts
representative of the colony as a whole.
Seabird 2000 represents the first attempt to census all inland
breeding colonies of Herring Gulls. However, only 1% of Herring
Gulls in Britain and Ireland breed away from the coast. Coverage in
Seabird 2000, although not complete, was comprehensive across the
different colony types and all major colonies and breeding areas
were censused. The largest gaps were in western and southern
Ireland, particularly the islands off Connemara (Galway) and the
mainland coast of west Cork. However, the former were covered
systematically during the 1995 all-Ireland tern survey and that
indicated very few significant Herring Gull colonies were present
in the area (Hannon et al. 1997). Surveys were not conducted in
inland Durham and of large roof-nesting colonies in Dumfries
(Dumfries and Galloway), Jarrow (Northumberland) and Sunderland
(Tyne & Wear) and in Dover & Folkstone (Kent). Elsewhere,
coverage of roof-nesting gulls was good, with the aid of aerial
surveys in places like south Wales, Gloucester, Glasgow and
Inverness.
Counts of breeding gulls within each admin area during Seabird
2000 and during previous censuses from gull surveys are presented
differently from other species to take into account the variation
in coverage of inland and coastal colonies during Seabird 2000 and
the previous two censuses. Since no inland colonies were surveyed
during Operation Seafarer (1969-70), Table 1 compares counts from
all three censuses from coastal colonies only, but also gives the
total number present in both inland and coastal colonies during
Seabird 2000. Table 3 gives counts of breeding Herring Gulls within
each admin area during Seabird 2000 and during two previous surveys
of roof-nesting gulls in Britain and Ireland, conducted in 1976
(Monaghan & Coulson 1977) and in 1993-95 (Raven & Coulson
1977).
[1] Coastal colonies were regarded as those being within 5km
of the high water mark; inland colonies were further from the sea
than this. All colonies in Orkney, Shetland and the Western Isles
were regarded as coastal.
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