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Grey Wagtail

Motacilla cinerea

Key facts

Conservation listings: Global: Least Concern
Europe: Least Concern
UK: red (breeding population decline)
Long-term trend: UK waterways: moderate decline
Population size: 38,000 pairs in 2009 (APEP13: 1988-91 Atlas estimate updated using CBC/BBS trend)
Grey Wagtail © Colin Varndell

Status summary

Grey Wagtails occur at highest densities along fast-flowing upland streams. WBS/WBBS shows a fluctuating population size along waterways, with a fall during the late 1970s and early 1980s from an initial high point in 1974, some increase since the late 1990s, and another steep drop around 2010. The BBS trend matches WBS/WBBS closely: there was an initial increase but from 2002 the trend was steeply downward, especially in Scotland. The species was moved from the green to the amber list in 2002, and subsequently from amber to the UK red list at the latest review in 2015 (Eaton et al. 2015). However, the long term decline is now categorised as moderate rather than rapid, as a result of a slight upturn since around 2012.

The trends for Grey Wagtail are very similar to those for Pied Wagtail, suggesting that similar factors may be affecting these two species. Clutch and brood size of Grey Wagtails rose as the population fell, and are now getting smaller again. Nest failure rates have dropped substantially, and there has been linear increase in the number of fledglings per breeding attempt, suggesting that reduced survival is the likely driver of decline. Numbers across Europe have been broadly stable since 1980 (PECBMS: PECBMS 2017a).

Data and graphs from this page may be downloaded and their source cited - please read this information

WBS/WBBS waterways graph
Smoothed population index, relative to an arbitrary 100 in the year given, with 85% confidence limits in green

Population changes in detail

Source Period
(yrs)
Years Plots
(n)
Change
(%)
Lower
limit
Upper
limit
Alert Comment
WBS/WBBS waterways 41 1975-2016 101 -36 -52 -19 >25
25 1991-2016 131 2 -12 16
10 2006-2016 144 -14 -25 -2
5 2011-2016 128 39 16 59
BBS UK 21 1995-2016 230 1 -12 19
10 2006-2016 271 -25 -34 -17 >25
5 2011-2016 236 28 15 43
BBS England 21 1995-2016 156 13 -6 37
10 2006-2016 190 -16 -27 -7
5 2011-2016 169 22 8 38
BBS Scotland 21 1995-2016 33 -11 -34 27
10 2006-2016 37 -41 -55 -19 >25
Tables show changes with their 90% confidence limits. Alerts are flagged for significant changes only. See here for more information.
BBS acknowledgement

WBS/WBBS waterways graph
WBS/WBBS waterways graph
BBS UK graph
BBS UK graph
BBS  England graph
BBS England graph
BBS  Scotland graph
BBS Scotland graph

Demographic trends

 
Clutch graph
Mean number of fledglings produced per nest - green bars represent standard error and black line shows long-term trend
Brood graph
Mean laying date in Julian days (1st April = Day 90) - green bars represent standard error and black line shows long-term trend
 

More on demographic trends

Variable Period
(yrs)
Years Mean annual
sample
Trend Modelled in
first year
Modelled in
2016
Change Alert Comment
Fledglings per breeding attempt 49 1967-2016 56 Linear increase 2.63 fledglings 3.38 fledglings 28.7%
Clutch size 49 1967-2016 40 Curvilinear 4.79 eggs 4.77 eggs -0.4%
Brood size 49 1967-2016 83 Curvilinear 4.05 chicks 4.15 chicks 2.5%
Nest failure rate at egg stage 49 1967-2016 60 Linear decline 1.72% nests/day 0.97% nests/day -43.6%
Nest failure rate at chick stage 49 1967-2016 59 Linear decline 2.05% nests/day 0.80% nests/day -61.0%
Laying date 49 1967-2016 63 Linear decline May 7 Apr 29 -8 days

For details of analytical methods for the Nest Record Scheme, the Constant Effort Sites (CES) and the Retrapping Adults for Survival (RAS) scheme, please follow links here.

Clutch graph
Mean number of eggs per nest - green bars represent standard error and black line shows long-term trend
Brood graph
Mean number of chicks per nest - green bars represent standard error and black line shows long-term trend
Egg survival graph
Proportion of nests failing per day during incubation - green bars represent 95% confidence limits and black line shows long-term trend
Nestling survival graph
Proportion of nests failing per day during incubation - green bars represent 95% confidence limits and black line shows long-term trend

Causes of change

Causes of population decline and fluctuation may be related to survival rates of juveniles or adults. At present there are not enough data to investigate this idea and more targeted studies, for example RAS projects or analyses to relate survival to weather variables, are needed.

Change factor Primary driver Secondary driver
Demographic Overwinter survival
Ecological Unknown

Further information on causes of change

Research has focused on the possible effects of water quality on this species. No correlation was found between Grey Wagtail breeding density and pH of streams in Scotland (Vickery 1991), a result supported by other authors who established that river acidity was less important than stream width, area of riffle and presence of bankside trees in influencing Grey Wagtail presence (Ormerod & Tyler 1987a). Laying date was three weeks later in acidic rivers than elsewhere in Wales, however, although clutch size, hatching success and brood size did not vary (Ormerod & Tyler 1991).

The species can feed in a range of habitats adjacent to rivers (Vickery 1991, Ormerod & Tyler 1987b) and do not rely on aquatic food sources (Ormerod & Tyler 1991): this may explain why they are less influenced by acidity of rivers, which has been associated with lower invertebrate abundance but not with Grey Wagtail abundance (Ormerod & Tyler 1991). Unhatched eggs collected over two years in Wales, Scotland and southwest Ireland did not contain toxic level of PCBs (Ormerod & Tyler 1992).

Causes of population decline and fluctuation appear to be related to survival rates. Targeted studies, for example RAS projects or analyses to relate survival to weather variables, have the potential to shed light on the population changes of this species.


Woodward, I.D., Massimino, D., Hammond, M.J., Harris, S.J., Leech, D.I., Noble, D.G., Walker, R.H., Barimore, C., Dadam, D., Eglington, S.M., Marchant, J.H., Sullivan, M.J.P., Baillie, S.R. & Robinson, R.A. (2018) BirdTrends 2018: trends in numbers, breeding success and survival for UK breeding birds. Research Report 708. BTO, Thetford. www.bto.org/birdtrends