Breeding abundance

Figure 1: Trend in UK abundance index of mew gull 1986-2010.

The annual sample of mew gull colonies is insufficient to produce reliable trend information. The graph shows an interpolated and extrapolated trend using population estimates obtained from censuses in 1985-88 and 1998-2002. Note that the only comparable census information between these two periods relates to coastal-nesting mew gulls, though in 1998-2002 inland breeders comprised about 60% of the total. The index indicates an increase of 66% between 1986 and 2009; in the longer term, census results for coastal nesters indicate an increase of 24% between 1969-70 and 1985-88.  The reason for the increase in abundance of coastal nesters is not known; it is possible that it may have been an artefact due to less complete coverage during the earlier censuses. American mink are known to have severe negative effects at a local level, taking both eggs, chicks and adults, and causing colony abandonment^1,2, though there appears not to have been a population level effect, perhaps due to control measures taken against mink.

Productivity

Figure 2: Trend in UK productivity (no. of chicks fledged per pair) of mew gull 1986-2010. Based on SMP data; view the methods of analysis (PDF 158 kb).

The sample of colonies for which productivity was studied may not be representative of the UK. Most information comes from a study of the effects of mink control on productivity of gulls and terns in western Scotland², which shows significant depressive effects of mink, for example by an estimated 46% in 2009³.

Population estimates and change 1969-2002 (census data)

* AON = Apparently Occupied Nests

Note: Inland colonies were not counted during the two earlier national censuses so to enable direct comparison the Seabird 2000 figure refers to the coastal population only.

Breeding Abundance

Figure 1: Trend in abundance index (solid line) of coastal-nesting mew gulls in Scotland, 1986-2010 with 95% confidence limits (dotted lines). Based on SMP data; view the methods of analysis (PDF 158 kb).

Coastal nesting mew gulls in Scotland have been increasing since 1969/70 according to national census data. Numbers recorded during Seabird 2000 were 26% higher than during the Seabird Colony Register, and 67% higher than during Operation Seafarer. The abundance trend using the SMP sample (Figure 1) agrees with the national census data over the same period, although suggests a slightly higher abundance at the time of Seabird 2000. The trend over the last decade was relatively stable until 2005 but has declined since then with the index in 2010 only 13% above that of 1986.

Numbers at some large inland mew gull colonies, not part of the analysis above, are known to have declined severely, for unknown reasons. For example, the first systematic survey of colonies at the Correen Hills (Gordon) and Mortlach Hills (Moray) in 1988-89 found 24,500 and 16,200 AON, respectively. By 1995 the Correen Hills colony had declined to 6,400 AON and by 1998 had become extinct. Decreases at the Correen Hills have been only partly been compensated by increases at the Mortlach Hills colonies and by the establishment of other colonies.

Productivity

Figure 2. Trend in productivity (no. of chicks fledged per pair) of mew gull in Scotland, 1986-2010. Based on SMP data; view the methods of analysis (PDF 158 kb).

Most information on the productivity of mew gull in Scotland comes from a study of the effects of mink control on productivity of gulls and terns on west coast islands², so may not be representative of Scotland as a whole. This mammal can have a significant depressive effects, for example by an estimated 46% in 2009 and 2010³. Trapping in recent years, specifically targeting colonies where the mink are most active, has helped to raise the number of young fledged. Trapping effort increased in the late 1990s but may have decreased since, possibly explaining the decline in productivity observed over the last decade.

Population estimates and change 1969-2002 (census data)

* AON = Apparently Occupied Nests

Note: Inland colonies were not counted during the two earlier national censuses so to enable direct comparison the Seabird 2000 figure refers to the coastal population only.

Breeding Abundance

Few mew gulls nest in England: eight pairs were recorded during Operation Seafarer rising to 31 pairs by the Seabird Colony Register. During Seabird 2000, numbers were found to have changed little since the previous survey. All coastal colonies occur from Norfolk to Kent, and generally hold fewer than 20 pairs.

Productivity

With only a handful of pairs nesting in England, few meaningful data on productivity are received. Monitored pairs tend to be in colonies containing terns which receive most of the targeted effort toward recording breeding performance. Complete failure is usually noticed and recorded but successful years less so. Hence, productivity data for this species is biased toward collecting zeros so the estimated average productivity of 0.17 chicks fledged per pair per year may be low because of this bias. 

Population estimates and change 1969-2002 (census data)

* AON = Apparently Occupied Nests

Note: Inland colonies were not counted during the two earlier national censuses so to enable direct comparison the Seabird 2000 figure refers to the coastal population only.

Breeding Abundance

This species no longer breeds in Wales. Two pairs were recorded during Operation Seafarer but none were found during the later censuses. 

Productivity

No data has been collected as part of the SMP.

Population estimates and change 1969-2002 (census data)

* AON = Apparently Occupied Nests

Note: Inland colonies were not counted during the two earlier national censuses so to enable direct comparison the Seabird 2000 figure refers to the coastal population only.

Breeding Abundance

Figure 1: Abundance of mew gull at Strangford Lough, 1986-2010.

Mew gull numbers at Strangford Lough (Figure 1) increased steadily from the late 1980s to 1999. A sharp decline then occurred during the early 2000s, although a count is missing for 2001 (when access restrictions due to foot and mouth disease were in place). This was followed by a rapid increase from 2002 onward with 532 pairs recorded in 2010, more than eighteen times that recorded in 1986. National census data show numbers increased greatly between Operation Seafarer and Seabird 2000. The steep increase at Strangford Lough during the last decade is likely to be representative of the national situation, as the largest colony in the region, on the Copeland Islands, has increased sevenfold since the previous census, and now holds over 700 pairs. Therefore, total numbers are now at least four times that recorded by Seabird 2000.

Productivity

Very few systematic data on the productivity of the mew gull have been collected in Northern Ireland as part of the SMP.

Population estimates and change 1969-2002 (census data)

* AON = Apparently Occupied Nests

Note: Inland colonies were not counted during the two earlier national censuses so to enable direct comparison the Seabird 2000 figure refers to the coastal population only.

Breeding Abundance

During Seabird 2000, 586 pairs of mew gull were recorded in the Republic of Ireland, five times as many as had been recorded by the Seabird Colony Register, but still 100 fewer pairs than were found by Operation Seafarer. Few data have been collected since, with no regular monitoring at all but the smallest colonies so the current status of the population is unknown.

Productivity

Very few systematic data on the productivity of the mew gull have been collected in the Republic of Ireland as part of the SMP.

Population estimates and change 1969-2002 (census data)

* AON = Apparently Occupied Nests

Note: Inland colonies were not counted during the two earlier national censuses so to enable direct comparison the Seabird 2000 figure refers to the coastal population only.

Breeding Abundance

National census data show numbers increased greatly between the Seabird Colony Register and Seabird 2000, after a large decline from that recorded by Operation Seafarer. Large increases have been recorded at colonies in Northern Ireland over the past decade but the trend in the Republic of Ireland is unknown due to few colonies of any size being surveyed. However, the total Irish population is currently above that recorded by Seabird 2000 as almost 1,300 pairs were recorded in 2010 from just a small sample of colonies.

Productivity

Very few systematic data on the productivity of the mew gull have been collected throughout Ireland as part of the SMP.

Population estimates and change 1969-2002 (census data)

* AON = Apparently Occupied Nests

Note: Inland colonies were not counted during the two earlier national censuses so to enable direct comparison the Seabird 2000 figure refers to the coastal population only.

Breeding Abundance

Only a few pairs of mew gull nest on the Isle of Man. Five pairs were found during the Seabird Colony Register and six pairs during Seabird 2000. No data have been received recently. 

Productivity

No systematic data on productivity have been collected as part of the SMP.

This species does not breed on the Channel Islands.