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Barn swallow

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Barn Swallow
European subspecies,
H. r. rustica in Denmark
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Aves
Order:
Passeriformes
Family:
Hirundinidae
Genus:
Hirundo
Species:
H. rustica
Binomial name
Hirundo rustica
Linnaeus, 1758

The Barn Swallow (Hirundo rustica) is the most common species of swallow. A distinctive passerine bird possessing blue upperparts, a long, deeply forked tail and curved, pointed wings, it occurs in Europe, Asia, Africa and the Americas.[2] It is often just called Swallow in northern Europe, where it is the only common member of the swallow family. The scientific name derives from two Latin words: hirundo meaning "swallow" and rusticus meaning "of the country".

There are several subspecies of the Barn Swallow breeding across the Northern Hemisphere and wintering further south. Its huge range means that the Barn Swallow is not endangered as a species. All its subspecies are migratory, and the wintering grounds cover most of the Southern Hemisphere down to northern Australia.

The Barn Swallow is a bird of open country which usually uses man-made structures to breed, and consequently has spread with human expansion. There are frequent cultural references in literary and religious works due to its close proximity to humans and annual migration. It builds a cup nest from mud pellets in barns or similar structures, and feeds on insects caught on the wing. The appearance and beneficial habits of this species mean that is tolerated by the humans with whom it lives so closely, and this acceptance was reinforced in the past by superstitions regarding the bird and its nest.

Description

Adult European subspecies in England

The adult male of the nominate European subspecies H. r. rustica is 17–19 cm long including 2–7 cm of elongated outer tail feathers. It has a wingspan of 32–34.5 cm and weighs 16–22 grams. It has steel blue upperparts and a rufous forehead, chin and throat, separated from the off-white underparts by a broad dark blue-black breast band. The outer tail feathers are elongated, giving the distinctive deeply-forked "swallow tail". There is a line of white spots across the outer end of the upper tail.[3]

The female is similar to the male, but the tail streamers are shorter, the blue of the upperparts and breast band is less glossy, and the underparts are paler. The juvenile is browner, has a paler rufous face and whiter underparts. It also lacks the long tail streamers.[2]

The song of the Barn Swallow is a cheerful warble, often ending with su-seer, the second note higher-pitched but falling. Calls include witt or witt-witt, and a loud splee-plink when excited.[3]. The alarm calls include a sharp siflitt for predators like cats, and a flitt-flitt for birds of prey like the Hobby.[4]

Although this species is distinctive in most of its range, in Africa the short tail streamers of the juvenile Barn Swallow invite confusion with juvenile Red-chested Swallow. However, the latter has a narrower breast band and more white in the tail.[5]

Taxonomy

The Barn Swallow was first formally described by Linnaeus in his Systema Naturae in 1758 as a member of the genus Hirundo.[6] This the only member of that genus to have a breeding range extending into the New World, the majority of Hirundo species being native to Africa. This genus of blue-backed swallows is sometimes called the "barn swallows".[2]

There are few taxonomic problems within the genus, but the Red-chested Swallow, Hirundo lucida, (Hartlaub, 1858) resident in West Africa, the Congo basin and Ethiopia was formerly considered to be a subspecies of Barn Swallow. Red-chested Swallow differs in being slightly smaller than its migratory relative, it has a narrower blue breast band, and the adult has shorter tail streamers. In flight, it also looks paler underneath.[5]

Subspecies

European subspecies,
H. r. rustica in Poland

The nominate European subspecies breeds in Europe and Asia, as far north as the Arctic Circle, south to North Africa, the Middle East and Sikkim, and east to the Yenisei River. It migrates on a broad front to winter in Africa, Arabia, and the Indian subcontinent.[2]

The subspecies H. r. transitiva, breeds in the Middle East from southern Turkey to Israel and is partially resident, but some birds winter in East Africa. It resembles the resident Egyptian subspecies H. r. savignii, since both have orange-red underparts, but the latter has a complete broad breast band and deeper red hue to the underparts.[2][4]

H. r. tytleri has deep orange-red underparts and an incomplete breast band. It breeds in central Siberia south to northern Mongolia and winters from eastern Bengal east to Thailand and Malaysia. It hybridises with H. r. gutturalis in the Amur area. It is thought that the two eastern Asia forms were once geographically separate, but the nest sites provided by expanding human habitation allowed the ranges to overlap.[2]

The subspecies H. r. gutturalis has whitish underparts and a broken breast band. It breeds from the eastern Himalayas to Japan and Korea. It winters across tropical Asia from India and Sri Lanka east to Indonesia and New Guinea. Increasing numbers are wintering in Australia. This subspecies wanders to northwestern North America, but is easily distinguished from the breeding subspecies there, which has reddish underparts.[2]

Asian subspecies H. r. gutturalis in Japan

The North American subspecies H. r. erythrogaster differs from the European subspecies in having redder underparts and a narrower, often incomplete, blue breast band. It breeds throughout North America, from Alaska to southern Mexico, migrating to the Lesser Antilles, Costa Rica, Panama and South America to winter.[7] A few may winter in the southernmost parts of the breeding range. Unlike the Eurasian race, which occurs as a vagrant in Alaska and Washington[8], this subspecies funnels through Central America on a narrow front, being abundant on passage in the lowlands of both coasts.[9]

Although over most of this swallow's range the subspecies are not contentious, in eastern Asia a number of additional or alternative forms have been proposed, including saturata, kamtschatica, and mandschurica. Given the uncertainties over the validity of these forms, [10] this article follows the treatments of Turner and Rose [2]

North American subspecies H. r. erythrogaster in Canada

Unexpectedly, DNA analyses show that Barn Swallows from North America colonised the Baikal region of Siberia, a dispersal direction opposite to that for most changes in distribution between North America and Eurasia. [11]

Behaviour

Habitat

The preferred habitat of the Barn Swallow is open country with low vegetation, such as pasture, meadows and farmland, and preferably near water. The Barn Swallow avoids heavily wooded or precipitous areas and densely built-up locations. The presence of accessible open structures like barns to provide breeding sites, and exposed locations such as wires, roof ridges or bare branches for perching, are also important in the breeding range.[3]

Feeding

In flight

Barn Swallows are similar in habits to the other aerial insectivores, including the other swallows and martins and the unrelated swifts (order Apodiformes). They are not particularly fast flyers (estimated at about 11 m/s)[12], but show remarkable manoeuvrability, necessary to feed on flying insects while airborne. They are often seen flying relatively low in open or semi-open areas. It is also estimated that they beat their wings approximately 7-9 times each second.[12]

They typically feed 7-8 m above shallow water or the ground, often following animals or humans to catch disturbed insects, but they will occasionally pick insects from the water surface, walls and plants. In the breeding areas, large flies make up around 70% of the diet, with aphids also a significant component. However, in Europe, Swallows take fewer aphids than House Martins or Sand Martins.[3] In the wintering area Hymenoptera, especially flying ants are important food items. When egg-laying, Barn Swallows hunt in pairs, but will form often large flocks otherwise.[2] The Barn Swallow drinks by skimming low over the surface scooping water with open mouth.[13]

After breeding, Swallows gather in communal roosts, sometimes thousands strong. Reedbeds are regularly favoured, the birds swirling en masse before swooping low over the reeds.[4] Reed beds are an important source of food prior to and whilst on migration. Although the Barn Swallow is a diurnal migrant which can feed on the wing whilst it travels low over ground or water, the reed beds enable fat deposits to be established or replenished. [14]

Breeding

Chicks and eggs in a North American nest which included horse hair lining

The male Barn Swallow returns to the breeding grounds first and selects a nest site, which is then advertised to females with a circling flight and song. The breeding success of the male is related to the length of the tail streamers, longer streamers being more attractive to the female.[3][15] Males with longer tail feathers are on average longer-lived and more disease resistant. Females therefore gain an indirect fitness benefit from this form of selection, since longer tail feathers indicate a genetically stronger individual which will produce offspring with enhanced vitality.[16]

Males with long streamers also have larger white tail spots. Since feather-eating Mallophaga lice prefer white feathers, large white tail spots without parasite damage again demonstrate breeding quality, and there is a positive association between spot size and the number of offspring produced each season.[17]

Both sexes defend the nest, but the male is particularly aggressive and territorial.[2] One established, pairs stay together to breed for life. However, extra-pair copulations are common, making this species genetically polygamous, despite being socially monogamous.[13]

Older chicks in nest

The Barn Swallow, as its name implies, typically nests inside accessible buildings such as barns and stables, or under bridges and wharves. The neat cup-shaped nest is placed on a beam or against a suitable vertical projection. It is constructed by both sexes (although more by the female) with mud pellets collected in their beaks, and lined with grasses, feathers or other soft materials.[2] Barn Swallows may nest colonially where sufficient high-quality nest sites are available. Colonies tend to be larger in North America. Within a colony, the pair defends a territory around the nest, which, for the European subspecies, is four to eight m2 in size.[13]

In North America at least, Barn Swallows frequently engage in a symbiotic relationship with Ospreys. Barn Swallows will build their nest below an Osprey nest, receiving protection from birds of prey which are driven away by the Ospreys (which eat only fish). The Ospreys are alerted to the presence of these predators by the alarm calls of the Swallows.[13]

Fledged young waiting to be fed

Before man-made sites became common, the Barn Swallow nested on cliff faces or in caves, but this is now rare. The female lays two to seven, but typically four or five, reddish-spotted white eggs. The eggs are 20 mm x 14 mm in size, and weight 1.9 g (of which 5 percent is shell). In Europe, the female does almost all the incubation, but in North America the male may incubate up to 25% of the time. The incubation period is normally 14–19 days, with another 18–23 days before the altricial chicks fledge. The fledged young stay with, and are fed by, the parents for about a week after leaving the nest. Occasionally, first-year birds from the first brood will assist in feeding the second brood.[2]

The Barn Swallow will mob intruders such as cats or accipiters that venture too close their nest, often coming within inches of the threat.[16] Adult Barn Swallows have few predators, but some are taken by accipiters, falcons, and owls. Brood parasitism by cowbirds in North America or cuckoos in Eurasia is rare.[13][3]

There are normally two broods, the nest being reused for the second brood, and repaired and reused in subsequent years. Hatching success is 90%, and fledging 70-90%. Average mortality is 70-80% in the first year and 40-70% for the adult. Although the record age is more than 11 years, most survive less than four years.[2]

The Barn Swallow has been recorded as hybridising with Cliff Swallow (Petrochelidon pyrrhonota) and Cave Swallow (P. fulva) in North America, and House Martin (Delichon urbicum) in Eurasia, the latter being one of the most common passerine hybrids.[16]·

Status

The Barn Swallow has an enormous range, with an estimated global extent of 10 million km². Its global population is estimated to be 190 million individuals. Although global population trends have not been quantified, the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as "least concern" on the 2007 IUCN Red List,[1] and has no special status under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) which regulates international trade in specimens of wild animals and plants.[13]

This is a species which has greatly benefited historically from forest clearance, which has created the open habitats it prefers, and from human habitation which have given it an abundance of safe man-made nest sites. There have been local declines through DDT in Israel in the 1950s, competition for nest sites with House Sparrows in the US in the 19th century, and an ongoing gradual decline in numbers in parts of Europe and Asia due to agricultural intensification reducing the availability of insect food. However, there has been an increase in the population in North America during the 20th century with the greater availability of nesting sites, and range expansion, including the colonisation of northern Alberta.[2]

Relationship with humans

A young male

The Barn Swallow is an attractive bird which feeds on flying insects, and has therefore been tolerated by humans when it shares their buildings for nesting. As one of the earlier migrants, this conspicuous species is also seen as an early sign of summer's approach.

It began to adapt to nesting in human structures around 300 years ago. It is believed North American birds began attaching their nests to Native American tepees in the early 1800s, and that birds in Europe subsequently began to use man-made structures and bridges. The spread of humans across North America is thought to have resulted in a dramatic population expansion across that continent. [11]

In literature

Many literary references are based on the Swallow's northward migration as a symbol of spring or summer. The proverb about the necessity for more than one piece of evidence goes back at least to Aristotle's Nicomachean Ethics: "For as one swallow or one day does not make a spring, so one day or a short time does not make a fortunate or happy man."[18]

The Swallow symbolizes the coming of spring and thus love in the Pervigilium Veneris, a late Latin poem. T. S. Eliot quoted the line "Quando fiam uti chelidon [ut tacere desinam]?" ("When will I be like the swallow, so that I can stop being silent?") This refers to a version of the myth of Philomela in which she turns into a swallow and her sister Procne into a Nightingale; in more familiar versions, the two species are reversed.[19] On the other hand, an image of the assembly of Swallows for their southward migration concludes John Keats's ode "To Autumn".

There are mentions of the Swallow in the Bible, although it seems likely that it is confused with the swifts in many translations,[20] and other hirundines also breed in Israel.[4] However, "Yea, the sparrow hath found her a house, And the swallow a nest for herself, where she may lay her young" from Psalms 84:3 is likely to apply to the Barn Swallow.[20]

The swallow is also notably cited in several of William Shakespeare's plays for the swiftness of its flight; for example: "True hope is swift, and flies with swallow’s wings..."Kings it makes gods, from act five of Richard III and "I have horse will follow where the game Makes way, and run like swallows o'er the plain." from the second act of Titus Andronicus. Shakespeare also references the annual migration of the species poetically in The Winter's Tale, act four: "Daffodils, That come before the swallow dares, and take The winds of March with beauty; violets dim,".

In culture

As a result of a campaign by ornithologists, the Barn Swallow has been the national bird of Estonia since 23 June 1960.[21][22]

Although Gilbert White was uncertain whether the Swallow migrated or hibernated in winter, its long travels have been well-observed. A swallow tattoo is popular amongst nautical men, and the tradition was that a sailor had a tattoo of this fellow wanderer after journeying 5000 nautical miles (9260 km, 5755 statute miles) at sea. A sighting of a swallow was a sign that land was near. [23]

In the past, the tolerance for this beneficial insectivore was reinforced by superstitions regarding damage to the Swallow’s nest. Such an act might lead to cows giving bloody milk, or no milk at all, or to hens ceasing to lay. [24] This may be a factor in the longevity of Swallows’ nests. Survival, with suitable annual refurbishment, for 10-15 years is regular, and one nest was said to have been occupied for 48 years.[24]

References

  1. ^ a b "BirdLife International Species factsheet: Hirundo rustica". BirdLife International. Retrieved 2007-11-15.
  2. ^ a b c d e f g h i j k l m n Turner, Angela K (1989). Swallows & martins : an identification guide and handbook. Houghton Mifflin. ISBN 0-395-51174-7. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ a b c d e f Snow, David (1998). The Birds of the Western Palearctic concise edition (2 volumes). Oxford: Oxford University Press. ISBN 019854099X 0-. {{cite book}}: Check |isbn= value: length (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  4. ^ a b c d Mullarney, Killian (1999). Collins Bird Guide. Collins. ISBN 0-00-219728-6. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  5. ^ a b Barlow, Clive (1997). A Field Guide to birds of The Gambia and Senegal. Pica Press. ISBN 1-873403-32-1. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  6. ^ Template:La icon Linnaeus, C (1758). Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Holmiae. (Laurentii Salvii). p. 824.
  7. ^ Hilty, Steven L (2003). Birds of Venezuela. London: Christopher Helm. ISBN 0-7136-6418-5.
  8. ^ Sibley, David (2000). The North American Bird Guide. Pica Press. ISBN 1-873403-78-4. {{cite book}}: Cite has empty unknown parameter: |1= (help)
  9. ^ Stiles, Gary (2003). A guide to the Birds of Costa Rica. Cornell University Press. ISBN 0-7136-6418-5. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  10. ^ Dickinson, Edward; Dekker, René. (2001) "Systematic notes on Asian birds. 13. A preliminary review of the Hirundinidae". Zool. Verh. Leiden 335 , 10.xii.2001: 127-144.— ISSN 0024-1652. Pdf retrieved 17 November 2007
  11. ^ a b Williams, Nigel (2006). "Swallows track human moves" Current Biology Volume 16, Issue 7, 4 April 2006, doi:10.1016/j.cub.2006.03.031 Text retrieved 16 November 2007
  12. ^ a b Park, Kirsty; Rosén, Mikael; Hedenström, Anders (2001) "Kinematics of the barn swallow (Hirundo rustica) over a wide range of speeds in a wind tunnel" The Journal of Experimental Biology 204, 2741–2750 (2001) Pdf retrieved 19 November 2007
  13. ^ a b c d e f Tanya; Roth, Chava. (2002). Hirundo rustica (On-line), University of Michigan Museum of Zoology Animal Diversity Web. Accessed November 19, 2007
  14. ^ Pilastro, Andrea "Euring Projects: The Euring swallow project in Italy" Euring Newsletter Volume 2, December 1998, Abstract retrieved 17 November 2007
  15. ^ Saino, Nicola; Romano, Maria; Sacchi; Roberto; Ninni, Paola; Galeotti, Paolo; Møller, Anders Pape (2003). "Do male barn swallows (Hirundo rustica) experience a trade-off between the expression of multiple sexual signals?" Behavioral Ecology and Sociobiology Volume 54, Number 5 September, 2003. doi 10.1007/s00265-003-0642-z Abstract retrieved 16 November 2007
  16. ^ a b c Møller, Anders Pape; Gregersen, Jens (illustrator) (1994) Sexual Selection and the Barn Swallow. Oxford: Oxford University Press ISBN 0198540280 Full text on Google Book Search, retrieved 16 November 2007
  17. ^ Kose, Mati; Mänd, Raivo: Møller, Anders Pape (1999) Sexual selection for white tail spots in the barn swallow in relation to habitat choice by feather lice Animal Behaviour Volume 58, Issue 6, December 1999, Pages 1201-1205 Abstract retrieved 18 November 2007
  18. ^ Welldon, J. E. C. (translator). The Nicomachean Ethics of Aristotle, Book 1, chapter 6. Macmillan. Retrieved 2007-11-18. {{cite book}}: |first= has generic name (help)
  19. ^ Nims, John Frederick (1981). The Harper Anthology of Poetry. Harper and Row. ISBN 0060448466.
  20. ^ a b Orr, James, (General Editor) (1915). "Definition for Swallow". International Standard Bible Encyclopedia 1915. On-line text retrieved 18 November 2007
  21. ^ The Estonian Embassy in London (on-line) Retrieved 19 November 2007
  22. ^ The Estonia Institute (on-line) symbols page Retrieved 17 November 2007
  23. ^ Vanishing tattoos (on-line) Retrieved 17 November 2007
  24. ^ a b Cocker, Mark (2005). Birds Britannica. Chatto & Windus. ISBN 0701169079. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
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