The Barn Swallow

Angela Turner

• Publisher: T & AD Poyser
• Year: 2010
• Print ISBN: 9780713665581
• eBook ISBN: 9781408128213
• Edition: 1
• Topic: Scienze biologiche
• Subtopic: Zoologia

The Barn Swallow is a familiar and popular bird throughout the world.

It is one of the most widely distributed bird species, breeding in North America, Europe, Asia and North Africa and wintering in South America, southern Africa, southern Asia and even northern Australia. Its habit of nesting close to human habitation has made this elegant bird a part of farmyard and village life and a welcome herald of spring.

This book examines all aspects of the life of this endearing bird, with chapters on its flying skills and feeding habits, mate choice, breeding strategies, nest sites, eggs and incubation, nestling rearing, productivity and survival, migratory behaviour and population dynamics. It also considers changes in populations and behaviour in relation to intensive agriculture and climate change.

The Barn Swallow is both engaging and authoritative; birdwatchers will enjoy amazing insights into the life of the species, such as the importance of tail feathers when finding a mate, or the sinister way that some birds kill of the chicks of rivals. Academic scholars will appreciate the book's broad overview of current research on this species.

CHAPTER 1

The swallows

The hirundines are a most inoffensive, harmless, entertaining, social, and useful tribe of birds.

Gilbert White, 1789

Barn Swallows are familiar birds in many parts of the world. Their willingness to nest and forage close to people has made them a part of the fabric of farmyard and village life. They are welcomed in spring, are a symbol of good luck and have a place in numerous legends and superstitions, as well as in poetry. They are popular among bird-ringers and scientists, too, and are among the most well-studied bird species in the world.

The Barn Swallow is one of 83 species belonging to the Hirundinidae, the family of birds comprising the swallows and martins (collectively known as hirundines) (Turner 2004). These small- to medium-sized passerines, ranging from the 10 g White-thighed Swallow to the 60 g New World martins, are all specialist aerial-feeders, pursuing and catching insects in flight. Consequently, they look rather similar with features such as a streamlined body, long wings and a forked tail that aid aerial hunting. Many have contrasting dark upperparts, often metallic blue or green, and paler white, buff or rufous underparts. They are also characterised by markings such as the red forehead and throat, the dark breast-band, and the white tail spots of the European Barn Swallow and the white rump of the Northern House Martin. Yet, despite these similarities, a fascinating diversity exists in their distribution, ecology and behaviour, between and sometimes within species.

Hirundines occur almost everywhere except the Arctic and Antarctic, but are most diverse in sub-Saharan Africa where some 30 species breed. The extent of the species’ distributions varies widely, though. The White-tailed Swallow, for example, occurs in a range of less than 15,000 km2 around Mega and Yavello, in southern Ethiopia; in contrast, the Barn Swallow breeds in North America, Europe, North Africa, and northern and central Asia. Hirundines are also found in many types of habitat, as long as there is a place to nest and open areas for feeding. Many breed in grasslands, along rivers and by wetlands. Those that associate with people now inhabit farmland, villages and towns. Although absent from dense forest, some, such as the Square-tailed Saw-wing, breed in forest clearings. Others, such as the White-banded and Black-collared Swallows, breed along forested rivers.

An intriguing aspect of the biology of hirundines is the way that many species build nests of mud. Others nest in pre-existing holes or make their own by burrowing. Although natural nest sites are still widely used by some species, others now use human artefacts, from nestboxes to bridges to our own homes. Indeed some, such as the Purple Martin and the Barn Swallow, now almost always nest in such sites. Another well-studied behaviour of hirundines is their sociality. Many species will nest close together and some, such as the Cliff Swallow, nest in large colonies. Only a few species, such as the Mangrove Swallow, are solitary nesters, defending a large territory.

Although many hirundines are still poorly studied, we know a great deal about a few species, including the Tree Swallow, Purple Martin, Collared Sand Martin and Cliff Swallow. The Barn Swallow itself has had more scientific papers written about it than have other hirundines, and probably most other birds. Indeed there are too many studies to mention; consequently I refer to reviews, such as Cramp (1988) and Brown & Brown (1999a), as much as possible. There are many studies of the biology of local populations. There are also long-term projects considering wider issues such as why females choose certain males as mates and why males have long outer tail feathers.

To give a flavour of the research on Barn Swallows, it is worth mentioning a few long-term studies. Since the 1970s, several aspects of the Barn Swallow’s biology, such as the energetics of breeding, have been studied at Stirling in central Scotland, and this is where I did my own study of the foraging behaviour of Barn Swallows (Turner 1980). In Denmark, Anders Møller has been studying Barn Swallows around Kraghede since 1971, initially looking mainly at mate choice and sexual selection and more recently factors affecting productivity and survival. There are also long-term studies in Spain and Italy on a variety of subjects such as songs, chick begging and immune function. Møller and other scientists are now collaborating on comparative studies of Barn Swallows in Finland, Estonia, Hungary and Algeria as well as Denmark, Italy and Spain. Barn Swallows affected by radiation from the nuclear accident at Chernobyl are also under study. In North America there have been several studies, particularly in New York State and Nebraska, investigating, for example, the costs and benefits of living in a group. There has been little research on mate choice and sexual selection in North American Barn Swallows, compared with that on European ones, but recent and ongoing studies are making up for this lack of knowledge. Barn Swallows are also the focus of various small and large-scale ringing projects. The main study is the EURING Swallow Project, which started in 1998, with the aim of studying the species’ population dynamics and dispersal patterns.

EVOLUTION AND TAXONOMY

Hirundines have a body design adapted for flight, and they form a distinctive family. As well as the streamlining of the body with a short neck and the long, pointed wings, hirundines have short legs with small, weak feet, and reduced leg muscles compared with other songbirds. The bill is short with a wide gape. The wings have ten primaries, with the outermost reduced. The tail has 12 rectrices and in many species it is forked, sometimes with elongated and narrowed outermost tail feathers. The tarsi are short and ridged at the back, and there is sometimes feathering on the toes and tarsi. A unique feature of typical hirundines lies in the structure of the syrinx, the resonating chamber at the bottom of the windpipe, which has more or less complete bronchial rings, instead of the half rings with a membrane at the front found in other songbirds. Two species, the African and White-eyed River Martins, though, stand out as being rather stocky with large bill, legs and feet; internally they have a large syrinx with half bronchial rings. Taxonomists thus put them in a separate subfamily.

Because of the similarities in structure and behaviour of the different species, and their distinctiveness from other songbirds, taxonomists have found it difficult to determine the relationships of hirundines among themselves and with other birds. Features such as nest type and plumage patterns have been useful in determining genera, but there have still been areas of uncertainty. However, studies using molecular techniques have made considerable progress in understanding the phylogeny of hirundines (Sheldon & Winkler 1993; Winkler & Sheldon 1993; Sheldon & Gill 1996; Sheldon et al. 1999, 2005).

The closest relatives of hirundines include the sylviid warblers, babblers, white-eyes, tits and chickadees, and bushtits, from which they diverged some 50 million years ago. Hirundines probably originated in Africa and southern Asia as far as Australia and then expanded into Europe and the New World. Some closely related species provide evidence of this in their relict populations: the Grey-rumped Swallow and the White-backed Swallow occur in Africa and Australia, respectively, and the river martins occur in Africa and south-east Asia, which suggests that their ancestors once had a more extensive distribution in Africa and Asia. The Grey-rumped and White-backed Swallows, along with the African saw-wings, are considered to be relict ‘primitive’ species. When hirundines extended their range beyond Africa and Asia is not known. The small fragile bones of hirundines rarely provide fossils, but a species (known as Hirundo aprica ) resembling the Barn Swallow was present 3.3–3.5 million years ago in North America.

The original hirundines probably excavated their own nest sites, as the modern sand martins do, burrowing into a riverbank or other soft substrate. They spread to the New World where they evolved into many genera that build nests in existing holes. These burrowing and hole-using hirundines are known as the ‘core martins’ and include a number of related groups: the Banded, Mascarene and Brazza’s Martins; the sand martins and tree swallows; the rough-wings and New World martins; and various endemic Neotropical genera.

The remaining hirundines probably originated from nest-excavating species in Africa, and comprise the 38 species that build mud nests, including the Barn Swallow. The majority of these species have sometimes been included in a single genus, Hirundo, and sometimes split into several genera. The latest studies support the classification of mud-nest-building hirundines into five genera, grouped into two clades. One clade comprises the barn swallows belonging to the genus Hirundo and the crag martins in the genus Ptyonoprogne, which build open-cup nests; the other comprises the house martins (Delichon), the cliff swallows (Petrochelidon) and the red-rumped swallows (Cecropis), which build enclosed nests.

The barn swallow group (the genus Hirundo ) can be divided into three clades (Table 1.1). The Barn Swallow itself is one of seven similar species, which have glossy blue upperparts, white tail patches and, apart from the White-throated Blue Swallow, paler underparts, and rufous on the head and often on the throat as well. The Barn, Red-chested and Ethiopian Swallows are particularly closely related and the Red-chested Swallow has been considered conspecific with the Barn Swallow. The Pacific and Welcome Swallows have also been considered conspecific.

The mud-nest-building hirundines have an advantage over hole-users and nest-excavators in that they can effectively build their own ‘hole’ and attach it to any vertical surface, in the absence of natural holes or soft substrates for burrowing. They have thus been able to breed in a variety of open habitats, as long as the climate is not too dry, when wet mud may be unavailable, or too wet, when the nest structure may be compromised. These species have spread from Africa and Asia into Australia, Europe and North America relatively recently and are continuing the invasion, with Barn Swallows now breeding, and Cliff Swallows attempting to breed, in South America.

Table 1.1. The species and ranges of the Barn Swallow genus Hirundo and their ranges.

DISTRIBUTION AND VARIATION

The Barn Swallow breeds in a broad band across Eurasia and North America, as far north as about 68° in Scandinavia and mostly to 63–66°N elsewhere (Figure 1.1). It occurs in a variety of habitats and climatic zones, being absent only from most of the Arctic tundra and from extensive areas of forest and deserts. Vagrants have reached many northerly points and oceanic islands such as northern Alaska, St Lawrence Island, the Pribilof and Aleutian Islands, Greenland, Jan Mayen, Bear Island, Spitsbergen, the Yamal Peninsula, Koryak Upland (north of Kamchatka), the Seychelles, the Hawaiian, Midway, Crozet and Falkland Islands, South Georgia and Tristan da Cunha (Kistchinskiy 1980; Danilov et al. 1984; Cramp 1988; Brown &Brown 1999a).

In the Old World, size and coloration of the underparts vary continuously, size declining from the northwest to the south and east (Cramp 1988). Eight subspecies are recognized (Figure 1.1). The nominate H. r. rustica Linnaeus, 1758 breeds in Europe and North Africa east to the Yenisey River, western China and the central Himalaya and winters mainly in sub-Saharan Africa. Breeding in the winter quarters is conceivable, as birds have been found in breeding condition in September in South Africa (A.P. Møller, pers. comm.). This is a large subspecies (wing length 125 mm in Scandinavia to 121 mm in Pakistan and northern India) with pale underparts, from buff-white to buff-rufous, and a full breast-band.

Two subspecies have localised distributions in Africa and the Middle East: H. r. savignii Stephens, 1817 (wing length 119 mm) in Egypt and H. r. transitiva (Hartert, 1910) (male/female wing length 126/121 mm) in Israel, Lebanon, Jordan and Syria. Both have full breast-bands like rustica, but savignii has dark rufous-chestnut underparts and transitiva is a paler rufous-buff. The Asian subspecies, in contrast, have a narrow breast-band and also differ in the shade of the underparts. There is not a sharp distinction between the subspecies, however, and the form of the breast-band varies clinally. Their breeding ranges require clarification. In eastern Asia, H. r. gutturalis Scopoli, 1786 is small (male/female wing length 116/115 mm) with pale creamy or white underparts. It occurs from the eastern Himalaya and southern, central and eastern China east to Taiwan, Japan and the Kuril Islands, and may breed irregularly in Kamchatka. It winters in southern and south-eastern Asia south to northern Australia. Birds in Sikkim, originally described as a separate subspecies ambigua, are sometimes included in rustica as they have an unbroken breast-band, but their size suggests they are probably nearer gutturalis (Dickinson & Dekker 2001). The darkest Asian subspecies, H. r. tytleri Jerdon, 1864 with uniform rufous-chestnut underparts (wing length 122 mm in Mongolia to 117 mm in southern Siberia), breeds in southern-central Siberia east to Yakutsk and south to northern Inner Mongolia, and winters from eastern India to south-east Asia. H. r. saturata Ridgway, 1883 (male/female wing length 116/115 mm) with rusty-ochre underparts breeds in Kamchatka south to the mid-Amur basin and east to the Sea of Okhotsk. It is not clear, however, whether breeding in Kamchatka is regular. H. r. mandschuricaMeise, 1934 (male/female wing length 114/112 mm) with light-ochre underparts breeds in north-eastern China. The subspecies saturata is often included in gutturalis or tytleri and mandschurica in saturata, although a recent comparison suggests the latter are separate (Dickinson & Dekker 2001; Dickinson et al . 2002). The Kamchatka population was also once designated a separate subspecies, kamtschatica Dybowski, 1883, but is now included in gutturalis/saturata. In west-central Asia, rustica intergrades with tytleri, and tytleri also intergrades with eastern populations. In the lower Amur basin, it is likely that gutturalis is a recent immigrant, arriving with Russian settlers in the seventeenth century, and has hybridised with the Barn Swallows already there (Smirensky & Mishchenko 1981).

The North American subspecies, H. r. erythrogaster Boddaert, 1783 (wing length 120 mm), breeds in North America from south Alaska, south Yukon, central-west Mackenzie, north Saskatchewan, north Manitoba, north Ontario, south-central Quebec and south Newfoundland south to north-west Baja California, Mexico south to Nayarit, Colima, Michoacán and Puebla, the Gulf Coast and north Florida. It is local or absent from only a few areas such as southern Florida, much of Arizona, south Nevada, south California, the higher parts of the Sierra Nevada in California, most of Baja California and coastal parts of Mexico (Brown & Brown 1999a). It winters in Central and South America and has also bred in Buenos Aires Province in Argentina since at least 1980 (Martinez 1983; Paynter 1995; Petracci & Delhey 2004). This subspecies has rufous-buff underparts and the breast-band is narrow and restricted to the sides of the breast. It is perhaps most similar to the east Asian subspecies, and indeed saturata, mandschurica and kamtschatica were once included in erythrogaster.

Figure 1.1. Breeding and main wintering ranges of the Barn Swallow.

The colour of the underparts is strongly variable both between and within populations, however (Cramp 1988). Darker birds can occur in a predominantly pale population and vice versa; for example, in Ukraine about 20% of birds have rufous-chestnut underparts, in Italy more than 10%, in Denmark nearly 4% and in Spain fewer than 2% (Møller 1994a, pers. comm.). In North America, individuals occasionally have whitish underparts; pale-bellied Barn Swallows breeding on islands alo...

Table of contents

• Cover
• Title Page
• Copyright Page
• Contents
• List of Figures
• List of Tables
• Acknowledgements
• Chapter 1 - The swallows
• Chapter 2 - Flight and feeding behaviour
• Chapter 3 - Social behaviour and vocalisations
• Chapter 4 - Attracting and choosing a mate
• Chapter 5 - Breeding strategies
• Chapter 6 - Nest sites and nests
• Chapter 7 - Eggs and incubation
• Chapter 8 - Chicks and parental care
• Chapter 9 - Productivity and survival
• Chapter 10 - Migration and dispersal
• Chapter 11 - Populations
• Appendix: Scientific names of plants and animals mentioned in the text
• Bibliography
• Plates