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). BBS data suggest increases throughout the UK since 1994. Analysis has shown that the population fluctuations are most strongly related to variable losses on their wintering grounds (Baillie & Peach 1992). 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). Annual survival rates from RAS sites in the UK for 1998–2004 were correlated positively with mean monthly rainfall during the early austral summer in southern Africa (Robinson et al. 2008). 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 apparently 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). Brood sizes increased up to the late 1980s, and may now be falling again. Climatic warming is leading to both an earlier start and later finish to the breeding season for European Swallows, but there has been increased chick mortality in hot, dry summers and reduced post-fledging survival because of poor conditions for birds migrating through North Africa (Turner 2009).

Population changes

Table of population changes for Swallow

Source	Period (yrs)	Years	Plots (n)	Change (%)	Lower limit	Upper limit
CBC/BBS England	39	1967-2006	439	23	-12	75
	25	1981-2006	649	19	-4	46
	10	1996-2006	1352	27	19	35
	5	2001-2006	1444	17	11	24
BBS UK	11	1995-2006	1679	32	26	39
	10	1996-2006	1736	28	22	34
	5	2001-2006	1901	13	9	17
BBS England	11	1995-2006	1285	28	22	37
	10	1996-2006	1323	25	19	33
	5	2001-2006	1444	16	10	21
BBS Scotland	11	1995-2006	149	31	13	50
	10	1996-2006	153	30	15	47
	5	2001-2006	160	11	1	27
BBS Wales	11	1995-2006	158	49	22	86
	10	1996-2006	166	36	14	63
	5	2001-2006	189	12	1	24
BBS N.Ireland	11	1995-2006	75	39	8	74
	10	1996-2006	81	33	8	56
	5	2001-2006	93	7	-8	19

Productivity trends

Table of productivity changes for Swallow

Variable	Period (yrs)	Years	Mean annual sample	Trend	Modelled in first year	Modelled in 2006	Change
Clutch size	38	1968-2006	220	Curvilinear	4.46 eggs	4.51 eggs	1.2%
Brood size	38	1968-2006	378	Curvilinear	4.07 chicks	4.12 chicks	1.3%
Daily failure rate (eggs)	38	1968-2006	280	None
Daily failure rate (chicks)	38	1968-2006	251	Linear increase	0.28% nests/day	0.53% nests/day	89.3%
Laying date	38	1968-2006	105	Curvilinear	Jun 20	Jun 12	-8 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., 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