 the trend recorded between 1994 and 2004 during which this colony declined by 12%. Many of the gannet colonies appear to have plenty of unused, suitable nesting habitat and thus have considerable potential for further expansion. Overall the Scottish population increased by 33% between the 2003/04 and 2013/14 gannet censuses, or by 2.9% per annum5.
Note: During analysis of the 2014 survey, the images used to assess the population at Bass Rock in 2009 were re-counted. This gave a revised colony total of 60,853 AOS for 20097, 5,371 AOS higher than the total given in previous editions of this report and elsewhere. However, this change for 2009 does not affect any of the data presented in the tables for the UK and Scotland.
Figure 3. Trend in breeding productivity (no. of chicks fledged per pair) of northern gannet in Scotland, 1986-2018. Based on SMP data; view the methods of analysis.
Data on northern gannet productivity have been collected each year at several gannetries in Scotland. Productivity at these monitored colonies has generally been high, seldom lower than 0.60 chicks fledged per pair, and appears to have increased over the study period. Productivity was low in the years 1987, 1990 and 1993, but the reasons for this are unclear. However, in 1993, productivity was severely reduced on Ailsa Craig due to poor weather (including snow and ice) in May. In 2015, northern gannet again had a successful breeding season on Ailsa Craig fledging 0.90 chicks per pair. During 2018, gannets in Scotland suffered a freezing spring followed by a very warm summer which may have contributed to the low productivity recorded that year (0.73 chicks fledged per pair).
**change between census in 2003-04 and colony surveyed in 2015.
Figure 4. Abundance of northern gannet at Bempton Cliffs, England, 1986–2017.
Only one northern gannet colony exists in England, at Bempton Cliffs in Humberside. This colony has been increasing steadily since its formation in the 1960s although, in recent years, the growth rate appears to have escalated. A steep increase can be seen between counts in 2004 and 2017, although there is an uncharacteristic decrease in 2005. Between 2008 and 2009 numbers increased by just over 900 AON from 6,954 to 7,859. During the survey in 2009, a further 1,470 non-breeding immature birds were counted in 'club' areas of the gannetry which suggested further increases could be expected. Predictably, the high rate of increase was sustained in 2017, when 13,392 nests were counted. On average, approximately 700 AON have been added each year since 2009. Gannets at Bempton Cliffs were not counted in 2018.
The productivity of gannets breeding at Bempton Cliffs shows no statistically significant variation over time; on average 0.80 chicks were fledged per nest between 1986 and 2018.
Figure 5. Abundance of northern gannet on Grassholm, Wales, 1986–2015.
There is just a single gannet colony in Wales, although occasionally single pairs have set-up territories elsewhere without colonies becoming established. Changes in the size of the Grassholm gannetry have been documented since its foundation around 1820. Since the 1940s, when 6,000 apparently occupied sites (AOS) were estimated, the colony has grown rapidly, with 15,500 AOS estimated by aerial survey in 1964. Since 1984, counts have been made from aerial photographs, varying in quality of resolution and coverage. In 2009, using high resolution digital images, 39,282 AOS were recorded – making it the third largest gannetry in the UK and Ireland. The most recent survey in 2015 counted 36,011 AOS.
Directly comparable with counts in 1984, 1999 and 2004, in terms of image quality and coverage, the 2015 count suggests that the colony has decreased by 8% since 2009.
Productivity data have been collected on Grassholm since 2002. Analysis shows no statistically significant variation over time; an average of 0.71 chicks are fledged per nest each year.
Northern gannet does not breed in Northern Ireland.
Census results indicate that northern gannet populations in the Republic of Ireland have been increasing since 1969/70. In 2004, when all gannetries in Ireland were counted, five colonies were known (Little Skellig, Bull Rock, Great Saltee Ireland’s Eye and Clare Island), supporting 36,111 AOS. A census of gannet colonies in Ireland in 2013–2014 showed an increase of 32.8% (47,946 AOS) compared to the 2004 census12. A new (sixth) colony on Lambay had established since the last census (in 2007) and significant increases at all sites were recorded, although Ireland’s Eye apparently reached capacity between 2004 and 2014. The largest proportion of the Irish population nests on Little Skellig, which held 29,683 AOS in 2004 and 35,294 AOS in 2014, an increase of 19%. Factors underlying the sustained growth of the Irish gannet population are not known, but food supply cannot be a limiting factor up to the present time. Recent changes to the EU Common Fisheries Policy have led to a reduction in discards which may, in due course, effect gannet population growth11. No northern gannet abundance data from the Republic of Ireland have been submitted to the SMP since 2015.
Data submitted to the SMP on the productivity of northern gannets in the Republic of Ireland are sparse; thus, no meaningful average productivity value can be given.
Within Ireland, the northern gannet only breeds in the Republic of Ireland. Thus, all data and text for the Republic of Ireland is also pertinent to the status of the species for the whole of Ireland.
This species does not breed in Northern Ireland and data submitted to the SMP on the productivity of northern gannets in the Republic of Ireland are sparse; thus, no meaningful average productivity value can be given.
Northern gannet does not breed on the Isle of Man.
Figure 6. Abundance of northern gannet on Ortac and Les Etacs, 1986–2015.
There are two gannetries in the Channel Islands, on Ortac and Les Etacs, which became established during 1940-45. Small in size compared to some other gannet colonies around the British and Irish coastlines, they nevertheless also show the familiar upward trend in numbers since Operation Seafarer visible at other gannetries. However, the most recent surveys, in 2015, recorded 2,777 AON on Ortac with 5,909 AON on Les Etacs. In summary, Les Etacs has apparently been increasing at a steady rate since 1986 while numbers on Ortac appear relatively stable over the same time period13.
Data submitted to the SMP on the productivity of northern gannets on the Channel Islands are sparse; thus, no meaningful average productivity value can be given.
1 Murray, S. and Wanless, S. 1986. The status of the Gannet in Scotland 1984–85. Scottish Birds, 14, 74–85.
2 Murray, S. and Wanless, S. 1997. The status of the Gannet in Scotland in 1994–95. Scottish Birds, 19, 10–27.
3 Murray, S., Wanless, S. and Harris, M.P. 2006. The status of the Northern Gannet in Scotland in 2003–04. Scottish Birds, 26, 17–29.
4 Wanless, S., Murray, S. and Harris, M.P. 2005. The status of Northern Gannet in Britain and Ireland in 2003/2004. British Birds, 98, 280–294.
5 Murray, S., Smith, I. and Smith, A. 2014. Gannet and Guillemot breeding on Rockall, North Atlantic. Scottish Birds, 34, 13–15.
6 Murray, S., Wanless, S. and Harris, M.P. 2014. The Bass Rock – now the world’s largest Northern Gannet colony. British Birds, 107, 765–769.
7 Murray. S., Harris. M.P. and Wanless, S. 2014. An aerial survey of Northern Gannets Morus bassanus on Scar Rocks, southwest Scotland, in 2014. Seabird, 27, 104–109.
8 Murray, S., Harris, M.P. and Wanless, S. 2015. The status of the gannet in Scotland in 2013-14. Scottish Birds, 35, 3-18.
9 Hamer, K.C., Phillips, R.A., Hill, J.K., Wanless, S. and Wood, A.G. 2001. Contrasting foraging strategies of Gannets Morus bassanus at two North Atlantic colonies. Marine Ecology Progress Series, 224, 283–290.
10 Cook, A.S.C.P. and Robinson, R.A. 2010. How representative is the current monitoring of breeding success in the UK? BTO Research Report, No. 573, BTO, Thetford.
11 Bicknell, A.W.J., Oro, D., Camphuysen, J.C. and Votier, S.C. 2013. Potential consequences of discard reform for seabird communities. Journal of Applied Ecology, 50, 649–658.
12 Newton, S.F., Harris, M.P. and Murray, S. 2015. Census of Gannet Morus bassanus colonies in Ireland in 2013-2014. Irish Birds, 10, 215