BTO - Breeding Birds of the Wider Countryside: Swallow

SWALLOW
Hirundo rustica

• Population
changes

• Productivity
trends

• Additional
information

Conservation listings

Europe: SPEC category 3 (depleted)
UK: amber (European status)

Long-term trend

UK, England: fluctuating, with no long-term trend

UK population size

726,000 territories in 2000 (1988–91 Atlas estimate updated using CBC/BBS trend: BiE04, APEP06)

Status summary

Swallow was originally amber-listed partly on the strength of a perceived CBC decline, but continues to qualify through its widespread decline across the European continent (BirdLife International 2004). Modern methods of estimating population change from CBC give evidence of fluctuations but not for long-term decline in the UK (Robinson et al. 2003). Detailed analysis has shown that the population fluctuations are most strongly related to losses on their wintering grounds (Baillie & Peach 1992). More recently, population change has been shown to be correlated with rainfall in the western Sahel prior to the birds' spring passage through West Africa, but with neither cattle numbers nor nest-site availability in the UK (Robinson et al. 2003). It is likely that, in eastern parts of the UK, the loss of livestock farming and grazed grassland, together with arable intensification, has caused the Swallow population to decline, while an increase in the area of pasture in the west and north has promoted a population increase which has more than compensated for declines elsewhere (Evans & Robinson 2004). A link between regional changes in the availability of preferred feeding habitats and the regional patterns of UK population change again suggests that habitat change on the breeding grounds may explain population trend, at least partly ( Henderson et al. 2007). Recent BBS data suggest increases throughout the UK since 1994. Brood sizes increased up to the late 1980s, and may now be falling again. The trend towards earlier laying can be partly explained by recent climate change (Crick & Sparks 1999).

Population changes

Table of population changes for Swallow

Source	Period (yrs)	Years	Plots (n)	Change (%)	Lower limit	Upper limit
CBC/BBS England	38	1967-2005	400	20	-13	68
	25	1980-2005	576	8	-14	31
	10	1995-2005	1260	28	22	35
	5	2000-2005	1330	14	9	21
BBS UK	10	1995-2005	1604	32	24	41
	5	2000-2005	1750	14	9	20
BBS England	10	1995-2005	1224	26	19	33
	5	2000-2005	1321	15	9	21
BBS Scotland	10	1995-2005	144	35	18	58
	5	2000-2005	148	16	5	30
BBS Wales	10	1995-2005	153	48	23	78
	5	2000-2005	180	15	1	31
BBS N.Ireland	10	1995-2005	73	39	8	77
	5	2000-2005	88	5	-10	19

Productivity trends

Table of productivity changes for Swallow

Variable	Period (yrs)	Years	Mean annual sample	Trend	Modelled in first year	Modelled in 2005	Change
Clutch size	37	1968-2005	201	None
Brood size	37	1968-2005	338	Curvilinear	4.07 chicks	4.14 chicks	1.7%
Daily failure rate (eggs)	37	1968-2005	254	None
Daily failure rate (chicks)	37	1968-2005	224	None
Laying date	37	1968-2005	97	Curvilinear	Jun 20	Jun 13	-7 days

Insufficient data on CES
available for this species

Additional information


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This report should be cited as: Baillie, S.R., Marchant, J.H., Crick, H.Q.P., Noble, D.G., Balmer, D.E., Barimore, C., Coombes, R.H., Downie, I.S., Freeman, S.N., Joys, A.C., Leech, D.I., Raven, M.J., Robinson, R.A. & Thewlis, R.M. (2007) Breeding Birds in the Wider Countryside: their conservation status 2007. BTO Research Report No. 487. BTO, Thetford. (http://www.bto.org/birdtrends) Pages maintained by Susan Waghorn and Iain Downie: Last updated 3 January, 2008