Swallow

Listen to example recordings of the main vocalisations of Swallow, provided by xeno-canto contributors.

This species can be found on the following statutory and conservation listings and schedules.

UK Birds of Conservation Concern	Green listed
Species of European Conservation Concern	Least Concern
IUCN Red List of Threatened Species (global)	Least Concern
Schedule 1 license required (to disturb)	No
Birds Directive Annex 1	No
Listed on the Annexes of	Bern(III)

Swallow was originally amber listed partly on the strength of a decline on CBC plots in the early 1980s, but later modelling of UK population change from CBC gave evidence of fluctuations but not of long-term decline (Robinson et al. 2003). Nevertheless, the species continued to qualify for amber listing through its 'depleted' status across the European continent (BirdLife International 2004). Following further review of its status in Europe, the species was moved to the UK green list in 2015 (Eaton et al. 2015). The trend has been broadly stable across Europe since 1980 (PECBMS: PECBMS 2020a>).

BBS data suggest shallow increases occurred in England, Scotland and Wales from 1995 until around 2010. The BBS map of change in relative density between 1994-96 and 2007-09, however, indicates that decreases had occurred during that period in Northern Ireland and in eastern coastal regions of Britain, with the strongest increases in western Britain. More recent BBS records indicate that declines have occurred in all four UK countries over the last ten years, reversing the earlier increases.

UK breeding population

-23% decrease (1995–2020)

Recorded breeding in 95% of 10-km squares, the Swallow has the most extensive distribution of any summer migrant in Britain & Ireland. It is absent only from a few areas of northern Scotland and from central London. It occurs at high densities throughout Ireland.

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Occupied 10-km squares in UK

No. occupied in breeding season	2860
% occupied in breeding season	95
No. occupied in winter	305
% occupied in winter	10

European Distribution Map

European Breeding Bird Atlas 2

Breeding Season Habitats

Most frequent in	Villages
Also common in	Pasture Farmland

Relative frequency by habitat

Relative occurrence in different habitat types during the breeding season.

Overall range size has changed little over the course of the atlases, although gains point to a small northward expansion.

Swallows usually arrive from April onwards with birds beginning to depart in September; stragglers may be present into October.

View a summary of recoveries in the Online Ringing Report.

Foreign locations of birds ringed or recovered in Britain & Ireland

View number ringed each year in the Online Ringing Report

Maximum Age from Ringing	11 years 1 months 11 days (set in 1936)
Typical Lifespan	2 years with breeding typically at 1 year
Adult Survival	0.374±0.011   (Male: 0.372±0.031 Female: 0.337±0.029)
Juvenile Survival	0.395 (in first year)

Wing Length	Adults	125.6±3.6 | Range 121–131mm, N=8326
	Juveniles	123±3.2 | Range 118-128mm, N=16641
	Males	126.7±3 | Range 122–131mm, N=3341
	Females	124.6±3 | Range 120–129mm, N=3795

Body Weight	Adults	19.9±1.75 | Range 17.2–23.0g, N=6897
	Juveniles	19.9±2.0234 | Range 17.5–22.3g, N=14764
	Males	19.9±1.69 | Range 17.4–23.0g, N=2776
	Females	19.8±1.79 | Range 17.1–23.0g, N=3157

Feather measurements and photos on featherbase

Ring size	A
Field Codes	2-letter: SL | 5-letter code: SWALL | Euring: 9920

For information in another language (where available) click on a linked name

Causes of change

The reasons for change are currently unclear. Although agricultural intensification is likely to be a primary driver, over-winter survival and changes in habitat on the breeding grounds may both be having an effect.

Further information on causes of change

Population fluctuations are most strongly related to variable levels of survival (Robinson et al. 2014), most likely on their wintering grounds (Baillie & Peach 1992). More particularly, annual 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). A review of research into threats to adult survival of several hirundine species, including Swallow, identified weather conditions throughout the annual cycle as a key threat (Imlay & Leonard 2019). There is also evidence suggesting that weather conditions experienced by Swallows during winter may have carry over effects which could affect breeding productivity the following summer (Saino et al. 2012).

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 size increased up to the late 1980s, however current data show no difference in brood size compared to the late 1960s, while nest losses have increased and the number of fledglings per breeding attempt shows no trend. A Danish study over 22 years found that the number of nesting pairs and the rate at which birds made feeding visits to nests declined in parallel with declines in insect abundance (Moller 2019); however numbers of fledglings were not counted by this study. Further evidence is therefore needed to confirm whether agricultural intensification and changes in insect abundance may have been sufficient to directly affect nest productivity and hence cause population changes at local and wider scales.

Climatic warming is leading to an earlier start to the breeding season for European Swallows, and analysis of phenological data has found that the arrival date in the UK has advanced, between the 1960s and 2000s, by 15 days (Newson et al. 2016), with the laying date also advancing (see above). Facey et al. (2020) found that nestling mass was negatively correlated with temperature, although the relationship with other weather conditions was complex and fledgling body mass was less sensitive to weather, hence the lower nestling body mass does not necessarily have any subsequent effect on juvenile survival and hence on population trends. However, Turner (2009) found that 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. A study in eastern Germany also highlighted reduced breeding success despite earlier breeding, and suggested that a mismatch between local and large-scale climatic changes may mean that, for this species, earlier breeding was not sufficient in that region to respond to climate change (Grimm et al. 2015).

Information about conservation actions

The decline of the Swallow in some parts of the UK may relate to agricultural intensification and changes of land use. There is evidence from several studies in Europe, including one in the UK, that the retention of cattle for meat or dairy farming may improve breeding performance and colony size and buffer Swallow declines ( Moller 2001 ; Evans et al. 2007; Gruebler et al. 2010; Ambrosini et al. 2012; Sicurella et al. 2014), with the presence of manure heaps also important ( Gruebler et al. 2010), and the presence of greater numbers of hayfields within 200 m of the colony increasing colony size at farms without livestock (Sicurella et al. 2014).

Artificial nests have also been suggested as a possible conservation option. In a study in Denmark, artificial nests had a low predation rate which was similar to natural nests, and showed higher breeding productivity. The author speculated that this could be due to the saving of energy and time costs from nest construction ( Teglhoj et al. 2018).