Breeding status of Merlins Falco columbarius in the UK in 2008

Figures & data

Figure 1. Distribution of 10-km squares occupied by Merlins in the UK between 1968 and 2007. Black squares indicate those surveyed by RSG members, and grey squares indicate those selected randomly for coverage by RSPB staff and volunteers in 2008. The white squares were not covered during the survey.

Table 1. Classification criteria for Merlin survey records.

Classification	Criteria
Breeding pair	Direct or indirect evidence of a breeding attempt. - nest with eggs or young found. - recently fledged young observed or heard. - used nest, eggshell fragments found. - adult leaving or returning to a nest site. A pair of Merlin engaging in courtship behaviour (copulation, food delivery, nest-site prospecting), or at least one Merlin showing territorial behaviour (repeatedly alarm calling, mobbing potential predator). A pair of Merlin seen during the breeding season at a potential breeding site. At least one Merlin holding territory (bird seen or heard at the same location on at least two visits separated by more than 1 week). Presence of accumulated signs (pellets, prey remains, whitewash, moulted feathers) indicating occurrence of breeding attempt.
Occupied territory	A single bird seen during the breeding season in apparently suitable habitat. Signs of Merlin occupation (but no birds sighted) at a location on two or more visits.

Figure 2. Populations of Merlins in regions with high levels of survey coverage in 1993–94 and 2008. The grey squares indicate the 10-km squares that received full coverage in both national surveys.

Table 2. Number of Raptor Study Group (RSG) and random 10-km squares covered and counts of occupied territories and breeding pairs in each country during the 2008 Merlin survey. Note that no RSG squares were surveyed in Wales in 2008.

Country	Number of RSG squares	No. of breeding pairs (and occupied territories) in RSG squares	No. of random squares	No. of breeding pairs (and occupied territories) in random squares
Scotland	118	161 (180)	41	41 (55)
England	78	101 (122)	10	16 (16)
Wales – Stratum 1	–	–	15	17 (21)
Wales – Stratum 2	–	–	9	5 (7)
Northern Ireland	15	10 (14)	7	2 (3)
UK	211	272 (316)	82	81 (102)

Table 3. National population estimates for Merlins derived from the 1993–94 and 2008 surveys, and percentage change across the two surveys. Numbers in parentheses represent the 95% confidence intervals of the estimates. Where estimates are not accompanied by confidence intervals, a complete survey was undertaken. In the ‘Change in population estimate (%)’ column, (n.s.) indicates that a bootstrap test showed the 1993–94 and 2008 did not differ significantly from one another at P = 0.05 (see methods).

Country	Occupied territories in 2008	Breeding pairs in 2008	Breeding pairs in 1993-94	Change in population estimate (%)
Scotland	947 (688–1238)	733 (512–979)	785 (602–994)	–7 (n.s.)
England	322 (173–518)	301 (151–496)	401	–25 (n.s.)
Wales	123 (76–178)	94 (62–130)	81	16 (n.s.)
Northern Ireland	49 (27–81)	34 (12–66)	–	–
Britain	1392 (1081–1720)	1128 (849–1427)	1291 (1108–1500)^a	–13 (n.s.)
UK	1441 (1116–1823)	1162 (891–1462)	–	–
^aThis total includes a minimum of 24 pairs estimated for areas where access was denied to fieldworkers (see Rebecca & Bainbridge 1998).

Table 4. Counts and estimates of population change for seven regional Merlin populations with high levels of survey coverage during the 1993–94 and 2008 national surveys. See Fig. 2 for information on the location of the regional populations. An asterisk (*) indicates the region is a Special Protection Area (SPA) with Merlin as a qualifying feature. Figures in parentheses in the ‘Breeding pairs in 2008’ column represent the expected site total for each SPA.

Regional population	Number of squares	Breeding pairs in 1993–94	Breeding pairs in 2008	% change in pairs
Orkney	13	16	17	6
Northeast Scotland	42	90	66	–27
Northumbria	17	39	12	–69
North York Moors*	13	36	19 (c. 35)	–47
South Pennine Moors*	14	55	29 (c. 58)	–47
Wales	17	29	18	–38
Southwest England	3	6	1	–83

Rebecca , G. W. and Bainbridge , I. P. 1998 . The breeding status of the Merlin Falco columbarius in Britain in 1993–94 . Bird Study , 45 : 172 – 187 .

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