Changes in the abundance and distribution of a montane specialist bird, the Dotterel Charadrius morinellus, in the UK over 25 years

Figures & data

Figure 1. The distribution of sites with suitable habitat for breeding Dotterel in Britain and regional boundaries used in analyses: (1) England & Wales, (2) South Scotland, (3) East Highlands, (4) Tayside Highlands, (5) Central Highlands, (6) SW Highlands, (7) West Highlands, (8) North Highlands. Unsurveyed sites, randomly selected sites and SPA/SSSI sites including the following: Ben Alder (SSSI & SPA); Beinn Dearg (SSSI & SPA); Lochnagar (SPA); Cairngorms (SSSI & SPA); Caenlochan (SSSI & SPA); Drumochter Hills (SSSI & SPA); Creag Meagaidh (SSSI & SPA); Ben Wyvis (SSSI & SPA); Monadhliath (SSSI); Fafernie (SSSI) and Beinn A’ Ghlo (SSSI). Glas Tulaichean was also included, as it is within the amended Cairngorms SPA although Dotterel is not a specific qualifying feature of the site.

Table 1. Survey coverage of potential breeding habitat in Visit 1 and Visit 2 of the 2011 UK Dotterel survey.

	Area potential breeding habitat		Visit 1				Visit 2
			Random		SPA/SSSI		Random		SPA/SSSI
Region	km^2	% Surveyed^a	No. Sites	Area (km^2)	No. Sites	Area (km^2)	No. Sites	Area (km^2)	No. Sites	Area (km^2)
1. England & Wales	36.7	45.9	2	1.3	0	0	10	16.9	0	0
2. South Scotland	21.3	52.3	3	5.5	0	0	6	11.1	0	0
3. East Highlands	199.4	68	17	25.6	37	105.1	19	29.9	38	105.7
4. Tayside Highlands	60	25.6	11	13.8	0	0	12	15.3	0	0
5. Central Highlands	94.4	52.9	20	24.3	11	22.9	24	27	11	22.9
6. SW Highlands	35.3	43.1	11	13.6	1	0.9	12	14.3	1	0.9
7. West Highlands	134.6	31.2	23	26.3	0	0	38	41.9	0	0
8. North Highlands	87.1	58.4	14	19.2	8	23.5	19	27.4	8	23.5
All	668.9	50.4	101	129.6	57	152.4	140	183.9	58	153

^a % Area potential breeding habitat surveyed in Visit 2.

Table 2. Calculation of population estimate replicates using bootstraps of random counts and correction factor estimates. Process completed for each region separately and regional population estimate replicates summed to give national population estimate replicates.

Region constants		Region bootstraps
SPA/SSSI count total	Unsurveyed area	Random counts	Correction factor	Corrected random counts	Extrapolate corrected random	Corrected SPA/SSSI counts	Region population estimate replicates
x	y	a1	b1	a1*b1 = C1	C1*y = D1	b1*x = E1	D1 + E1 = F1
		.	.	.	.	.	.
		.	.	.	.	.	.
		a99	b999	a999*b999 = C999	C999*y = D999	b999*x = E999	D999 + E999 = F999

Figure 2. The distribution of sites occupied during the first visit (pre-breeding) and second visit (breeding) surveys.

Figure 3. Occupied and unoccupied sites surveyed in Scotland in each National survey; (a) 1987/88, (b) 1999 and (c) 2011.

Table 3. Percentage of survey sites occupied (number sites surveyed in brackets) and regional densities of breeding Dotterel during each national survey (corrected number of breeding males/total area surveyed).

	(a) Percentage of survey sites occupied (%)			(b) Breeding density (males/km^2)
Region	1987/88	1999	2011^a	1987/88	1999	2011^a
1. England & Wales	50 (6)	0 (6)	0 (10)	0.24	0.00	0.00
2. South Scotland	18 (11)	10 (10)	0 (6)	0.11	0.06	0.00
3. East Highlands	77 (52)	51 (55)	35 (57)	2.91	2.06	1.53
4. Tayside Highlands	30 (10)	13 (8)	0 (12)	0.43	0.46	0.00
5. Central Highlands	68 (19)	39 (28)	31 (35)	1.90	2.05	0.92
6. SW Highlands	43 (7)	13 (8)	8 (13)	0.33	0.21	0.13
7. West Highlands	56 (36)	17 (36)	5 (38)	0.67	0.34	0.29
8. North Highlands	44 (32)	39 (23)	11 (27)	0.92	1.18	0.71
All	57 (173)	33 (174)	19 (198)	1.60	1.35	0.90

^aData presented here from Visit 2 only.

Table 4. Numbers of breeding male Dotterel (plus 95% confidence intervals) and estimates of population change from the three national surveys.

	1987/88	1999	2011	% Change
	Breeding males	Breeding males	Breeding males	1987/88 to 2011	1999–2011
1. England & Wales	9 (4–21)	0	0	−100	–
2. South Scotland	2 (1–4)	2 (0–16)	0	−100	–
3. East Highlands	580 (496–667)	380 (337–619)	257 (170–396)	−55.7	−32.4*
4. Tayside Highlands	26 (13–53)	29 (0–90)	0	−100	−100
5. Central Highlands	181 (132–248)	205 (81–426)	72 (39–139)	−60.2	−64.7
6. SW Highlands	11 (5–27)	8 (0–45)	5 (0–24)	−54.5	−39.9
7. West Highlands	91 (68–104)	28 (14–63)	39 (0–112)	−57.1	37.6
8. North Highlands	81 (63–104)	95 (73–216)	49 (21–135)	−39.5	−48.2
All	981 (873–1101)	747 (676–1232)	423 (279–644)	−56.9	−43.3*

*Statistically significant at P < 0.05.

Table 5. Pairwise comparisons of estimated numbers of breeding Dotterel on sites surveyed (a) in each national survey 1987/88, 1999 and 2011 and (b) in 2011 national survey and in ongoing monitoring 2012 and 2013. Z-scores, two tailed probability values and effect size (r) are shown above the diagonal (number of sites in brackets), the year with the greater number of Dotterel below the diagonal (if P< 0.05).

(a)	1987/88	1999	2011
1987/88		Z = −3.54, P < 0.001, r = −0.29 (77)	Z = −4.42, P < 0.001, r = −0.38 (67)
1999	1987/88)>		Z = −2.73, P = 0.006, r = −0.26 (55)
2011	1987/88 >	1999 >
(b)	2011	2012	2013
2011		Z = −0.310 P = 0.765, r = −0.04 (23)	Z = −0.398, P = 0.698, r = −0.05 (33)
2012	–		Z = 0.480, P = 0.6411, r = 0.07 (26)
2013	–	–