Danielle Nugent Professor Cromartie

Essay 1-A Family and its NicheHirundinidae

Swallows belong to the Hirundinidae family; this family of songbirds also includes

martins. They are known for their playful whimsical flight, quick movements, and sudden

changes in direction. The ecological niche of the Hirundinidae family encompasses a wide

range around the world. These songbirds have made adaptations to their habitats and lifestyle

in order to be successful. Two evident adaptations are their wing morphology and ability to

construct specialized nests pertaining to their environment. These adaptations along with

several others have allowed the Hirundinidae family to be successful.

The Hirundinidae family consists of swallows and martins with about 89 species in 15

genera worldwide. To the inexpert eye, swallows look distressingly similar. The Hirundinidae

family is composed of small to medium-sized songbirds about four to nine inches long. They

have long pointed wings with either forked or square tails. Swallows tend to have more of a

forked tail and martins tend to have a squarer tail. Both swallows and martins have short wide

bills and inconspicuous legs. These birds are excellent fliers and perches, but have difficulty

walking due to their short leg morphology (Parker, 1982). Their plumage varies from brown,

gray, iridescent blue or green, with contrasting patches of reddish brown or white in some

species. Most species of swallows are sexually dimorphic (Elphick, Dunning, & Sibley, 2001).

These characteristics make the Hirundinidae family unique from other species of birds.

Hirundinidae can be classified as phylum Chordate, class Aves, and order Passeriformes.

Their taxonomy is well known especially the species in North America. Through recent

comparisons of DNA and plentiful information on history, the genealogy and evolution of this

family is well understood. However, the assignment of species to genera remains unclear due

to taxonomists debate as to what constitutes as a genus among them. The genera worldwide

ranges from 10 to 35, and currently is considered 15 (Elphick, Dunning, & Sibley, 2001).

Attempts to find Hirundinidae common ancestors have been conducted by comparing DNA

sequences. Although there is no definite answer, it has been found members of this family

loosely belong to a large conglomeration of passerine birds, including Old World warblers,

babblers, titmice, and many other small insectivores (Elphick, Dunning, & Sibley, 2001). DNA

sequence comparisons uncovered that swallows are monophyletic and are composed of two

clades, river martins (Pseudochelidoninae) and the typical swallows (Hirundininae).

Hirundinidae can be further split into three divisions mud nesters, core martins, and basal

relicts. Although DNA sequencing can successfully identify different divisions, their common

ancestor remains a mystery. Moyle et al. (2005) concluded that “a more likely explanation for

their distribution is that their progenitors once occurred from Africa across southern Asia to

Australia, and they subsequently became extinct in southern Asia.” Although swallows

behavior and ecology are well understood, their phylogeny remains unclear.

The Hirundinidae family can be found worldwide on every continent besides Antarctica.

The greatest diversity is found in Africa and South America. Roughly nine in six genera species

can be found in North American, there are also five accidental species (Elphick, Dunning, &

Sibley, 2001). Seasonal migration is an adaptation in response to changes of weather. Like

many other birds, swallows and martins generally breed in temperate regions and migrate to

warmer areas to spend the winters (Walters, 2011). According to Thompson III (2005),

swallows are migratory birds and usually migrate in large mixed-species roosting flocks in late

summer before migrations.

Swallows diet consists almost exclusively of aerial insects. They are excellent agile fliers

and have the ability to catch insects and drink water on their wings (Parker, 1982). In the

Hirundinidae family, different species have adapted specialize hunting styles. The Violet-green

Swallow (Tachycineta bicolor), Cliff Swallow (Petrochelidon pyrrhonota), and Purple Martin

(Progne subis) tend to feed at higher altitude than other species. During breeding season Barn

Swallows (Hirundo rustica) and Northern Rough-winged Swallows (Stelgidopteryx serripennis)

feed at lower altitudes over water and fields. Generally swallows like to feed in open habitats

over large fields or low water. One example of a specific adaptation in the Hirundinidae family

is found in the Tree Swallow (T. bicolor). Tree Swallows can feed on berries during the winter

when insects become scarce. Tree Swallows are the only species capable of digest the wax in

bayberries (Elphick, Dunning, & Sibley, 2001).

Swallows have also shown their ability to evolve their niche through nest construction.

Nest construction is more diverse in the Hirundinidae than any other family of oscine birds.

Nest construction can be traced back through their evolutionary history. Swallows have

developed three alternative strategies of nesting: burrowing, cave-adopting, and mud nest.

Burrowing has been found to be the primitive form of nesting. Cavity-adopting and mud-

nesting clades branched off from burrowers. Mud nester are part of the New World birds, they

have been shown to increase in complexity. Researchers Sheldon and Winkler (1993) have

found that “the use of mud by swallows appears to be independently derived from its use in

nest building by other birds; swallows are apparently the only birds that build an elevated

attached nest composed entirely of mud.” More than half mud nesters live in Africa; due to the

environment, they have had to alter their nesting habits in order adapt to their environment

(Elphick, Dunning, & Sibley, 2001).

Breeding sociality in Hirundinidae family greatly varies. Each species has a different

style of breeding. Some like the Northern Rough-winged Swallow (S. serripennis) are dispersed

breeders, meaning they do not nest in clusters but spread out. Some like the Barn Swallow (H.

rustica) and the Purple Martin (P. subis) are fundamentally territorial and tend to nest under

bridges. And others like the Cliff Swallow (P. pyrrhonota) and Bank Swallow (Riparia riparia) are

obligate colonial nesters. Colonial nesters live in colonies of several to thousands of nests; this

method of nesting has its disadvantages, but also advantages. Disadvantages include being

more susceptible to predators and parasites. Being close together can be a disadvantage for

swallows because it makes them easy prey; for example, a snake can easily go from nest to nest

devastating a colony. The advantages to colonial nesters include the ability to communicate and

share information about food (Elphick, Dunning, & Sibley, 2001).

Humans have created an interesting paradox for members of the Hirundinidae family.

Human activity has increased the number of Barn Swallows (H. rustica), Cliff Swallows (P.

pyrrhonota), Cave Swallows (Petrochelidon fulva), Tree Swallows (T. bicolor), and some

subspecies of Purple Martins. On the other hand, development has dramatically decreased

swallows native habitats. Species like the Purple Martin (P. subis) and Tree Swallow (T. bicolor)

have had to relocate and change their way of life (Elphick, Dunning, & Sibley, 2001). There is no

research on the effects of deforestation, agriculture, and pollution but it is predicted that these

factors have a negative impact on swallows, reducing the number of nest sites and prey.

Swallows and martins are especially adapted to aerial life. “The nature of the

evolutionary forces that produced such limited ranges in birds with such strong flight remains

one of the most intriguing problems in swallow biology” (Elphick, Dunning, & Sibley, 2001).

Swallows are known for their flight, it has been their key to evolution. “Avian flight morphology

is affected by a mixture of selection pressures and is thus an interesting example of how

different selection forces initiate changes in morphological traits” (Florentino et al., 2004).

Swallows are known for their unique flight patterns. Although their wings are beautiful there is

more to them then appearance. It is now understood that tails morphology is favored by

nature rather than sexual section. Swallows use their wings as an advantage for catching prey

and avoiding predators. Tail morphology plays a vital role in their ability to fly. Longer tails

cause aerodynamic drag; shorter tails allow for swallows to make tighter turns. This is

extremely helpful when it comes to their hunting strategies. Tighter turns are beneficial during

foraging. Streamers are beneficial to maneuverability but have a detrimental impact on

velocity and acceleration. Short narrow streamers are more beneficial for hunting food.

Depending on their diet swallows have evolved and developed different tail morphology.

Swallows that prey on larger insects generally tend to have larger tail streams to aid in

maneuverability. Swallows that prey on smaller insects have developed shorted tail streamers

in order to increase their velocity, and acceleration (Lope et al., 2004).

In the words of Charles Darwin, “it is not the strongest of the species that survive nor

the most intelligent, it is the one that is most adaptable to change.” Organisms adapt to their

environment in order to survive. After examining the Hirundinidae family as a whole, several

adaptations stand out in their ecological niche: their ability to alter their nest construction to fit

their environment and their physiological wing morphology. In the case of the Hirundinidae

family, their success for evolution and struggle for existence lies within their wing morphology.

Literature cited

Dunning, Elphick, & Sibley D. (2001). The Sibley Guide to Bird Life and Behavior. Alfred a Knopf

Inc. New York. Pp 351.

Lope et al. (2004). Vane emargination of outer tail feathers improves flight manoeuvarbility in

Streamerless Hirundines, Hirundinidae. Biological Sciences, 271, 1831- 1838.

Moyle et al. (2005). Phylogeny of swallows (Aves: Hirundinidae) estimated from nuclear and

mitochondrial DNA sequences. Molecular Phylogenetic and Evolution, 35, 254-270.

Parker, S. (1982). Synopsis and Classification of Living Organisms McGraw-Hill. New York, New

York.

Sheldon and Winkler. (1993). Evolution of nest construction in swallows (Hirundinidae): A

molecular phylogenetic perspective. National Academy of Science, 90, 5705-5707.

Thompson III. (2005). Identify Yourself The 50 Most Common Birding Identification Challenges.

Houghton Mufflin Company. New York. Pp 392

Walters. (2011). Bird Watch. The University of Chicago Press. Chicago. Pp 227.