BTO - Breeding Birds of the Wider Countryside: Blackbird

BLACKBIRD
Turdus merula

• Population
changes

• Productivity
trends

• Additional
information

Conservation listings

Europe: no SPEC category (concentrated in Europe, conservation status favourable)
UK: green

Long-term trend

UK, England: shallow decline

UK population size

4,935,000 territories in 2000 (1988–91 Atlas estimate updated using CBC/BBS trend: BiE04, APEP06)

Status summary

Both CBC/BBS and CES data show long-term declines in Blackbird abundance, but recent increases suggest that the population has begun to recover. The moderate-decline criteria for amber listing and for BTO alerts are no longer met, and the species is now listed in the green category. CBC results indicate that the decline began in the mid 1970s. Nest success has improved over this period, and it is likely that reduced survival drove the decline (Siriwardena et al. 1998a). Agricultural intensification is likely to have contributed (Fuller et al. 1995), but, since numbers fell in woodland as well as farmland, additional factors probably operated.

Population changes

CBC/BBS UK graph

Table of population changes for Blackbird

Source	Period (yrs)	Years	Plots (n)	Change (%)	Lower limit	Upper limit	Alert	Comment
CBC/BBS UK	39	1967-2006	828	-16	-23	-7
	25	1981-2006	1166	2	-5	9
	10	1996-2006	2292	21	18	24
	5	2001-2006	2406	4	2	6
CBC/BBS England	39	1967-2006	671	-18	-25	-10
	25	1981-2006	938	-1	-9	6
	10	1996-2006	1823	19	16	22
	5	2001-2006	1893	3	2	5
CES adults	22	1984-2006	96	-13	-25	0
	10	1996-2006	107	-9	-15	0
	5	2001-2006	97	-17	-23	-10
CES juveniles	22	1984-2006	86	-25	-45	0	>25
	10	1996-2006	97	8	-4	24
	5	2001-2006	91	12	-7	35
BBS UK	11	1995-2006	2128	22	19	26
	10	1996-2006	2190	20	17	23
	5	2001-2006	2406	5	4	7
BBS England	11	1995-2006	1691	20	17	24
	10	1996-2006	1735	18	16	21
	5	2001-2006	1893	4	2	6
BBS Scotland	11	1995-2006	165	28	12	46
	10	1996-2006	168	28	14	46
	5	2001-2006	180	12	2	21
BBS Wales	11	1995-2006	183	40	29	50
	10	1996-2006	191	37	27	45
	5	2001-2006	223	17	12	21
BBS N.Ireland	11	1995-2006	77	40	10	55
	10	1996-2006	83	20	-1	27
	5	2001-2006	95	-10	-17	-4

CBC/BBS England graph

CES adult abundance graph

CES juvenile abundance graph

BBS UK graph

BBS England graph

BBS Scotland graph

BBS Wales graph

BBS N Ireland graph

Productivity trends

Table of productivity changes for Blackbird

Variable	Period (yrs)	Years	Mean annual sample	Trend	Modelled in first year	Modelled in 2006	Change	Comment
Clutch size	38	1968-2006	118	None
Brood size	38	1968-2006	151	Curvilinear	3.35 chicks	3.38 chicks	1%
Daily failure rate (eggs)	38	1968-2006	179	Curvilinear	2.57% nests/day	3.65% nests/day	42%
Daily failure rate (chicks)	38	1968-2006	154	Linear decline	3.03% nests/day	1.92% nests/day	-36.6%
Laying date	38	1968-2006	143	None
Juvenile to Adult ratio (CES)	22	1984-2006	98	Smoothed trend	122 Index value	100 Index value	-18%
Juvenile to Adult ratio (CES)	10	1996-2006	109	Smoothed trend	89 Index value	100 Index value	12%
Juvenile to Adult ratio (CES)	5	2001-2006	100	Smoothed trend	77 Index value	100 Index value	30%

Clutch size graph

Brood size graph

Egg nest failure graph

Chick nest failure graph

Laying date graph

CES productivity graph

Additional information


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This report should be cited as: Baillie, S.R., Marchant, J.H., Leech, D.I., Joys, A.C., Noble, D.G., Barimore, C., Grantham, M.J., Risely, K. & Robinson, R.A. (2009). Breeding Birds in the Wider Countryside: their conservation status 2008. BTO Research Report No. 516. BTO, Thetford. (http://www.bto.org/birdtrends) Pages maintained by Iain Downie, Mandy T Andrews and Laura Smith: Last updated 18.02.2009