Purple Martin

## Description

The purple martin (Progne subis ) is a passerine bird in the swallow family Hirundinidae. It is the largest swallow in North America. Despite its name, the purple martin is not truly purple. The dark blackish-blue feathers have an iridescent sheen caused by the refraction of incident light giving them a bright blue to navy blue or deep purple appearance. In some light they may even appear green in color.

Being migratory, their breeding range extends from central Alberta down through the eastern United States. Subspecies breed in Baja California, Arizona, and New Mexico. Most make a brief stopover in the Yucatán Peninsula or Cuba during pre-breeding migration to North America and during post-breeding migration before reaching their overwintering site in South America.

They are known for their speed, agility, and their characteristic mix of rapid flapping and gliding flight pattern. When approaching their nesting site, they will dive from the sky at great speeds with their wings tucked.

## Appearance

The Purple martin is the largest swallow in North America. Despite their name, these birds are not truly purple. Their dark blackish-blue feathers have an iridescent sheen caused by the refraction of incident light giving them a bright blue to navy blue or deep purple appearance. In some light, they may even appear green in color. Adult males are entirely black with glossy steel blue sheen, the only swallow in North America with such coloration. Adult females are dark on top with some steel blue sheen and lighter underparts. Adults have a slightly forked tail.

## Distribution

Purple martins breed across eastern North America, and also some locations on the west coast from British Columbia to Mexico. In winter, these birds migrate to the Amazon basin. Purple martins inhabit open areas near wetlands, swamps, and wet meadows. They can be found along forest edges, in mountain forests, shrubland, agricultural areas, farms, and in urban settlements.

## Behavior

Purple martins are diurnal social birds; they live and breed in colonies but prefer forage in small groups or in pairs. These birds are agile hunters and eat a variety of winged insects. They primarily feed by hawking, a strategy of catching insects in the air during flight. Rarely, they will come to the ground to eat insects. Purple martins migrate to North America in the spring to breed. Older males typically migrate first and leave the overwintering sites in late December or early January, followed by older females. Younger birds (first yearlings) typically arrive at the breeding grounds up to two months later. When the breeding season is over, Purple martins head south. Some birds leave as early as July and others stay as late as October. Martins generally migrate over land, through Mexico and Central America. When not breeding, martins form large flocks and roost together in great numbers. This behavior begins just prior to the southern migration and continues on the wintering grounds. Purple martins are fairly noisy, chirping, and making sounds that can be described as chortles, rattles, and croaks. The various calls are said to be "throaty and rich" and can be rendered as tchew-wew, pew pew, choo, cher, zweet and zwrack. The males have a gurgling and guttural courtship song, a dawn song, and even a subsong used at the end of the breeding season.

## Diet

Purple martins are carnivores (insectivores). Their diet consists of various insects including fire ants, bugs, flies, butterflies, dragonflies, grasshoppers, crickets, moths, wasps, bees, cicadas, some spiders, and termites.

## Reproduction

Purple martins are serially monogamous and form pairs that last within one nesting season. However, they may also exhibit polygynous behavior when one male may mate with more than one female. Breeding season occurs during May and June. Males arrive in breeding sites before females and establish their territory. A territory can consist of several potential nest sites. After forming a pair, both the male and female inspect available nest sites. Purple martins make their nests in cavities, either natural or artificial. In many places, humans put up real or artificial hollow gourds or houses for martins. The nest is made inside the cavity of such artificial structures and retains a somewhat flat appearance. The nest is a structure of primarily three levels: the first level acts as a foundation and is usually made up of twigs, mud, small pebbles, and even small river mollusk shells; the second level of the nest is made up of grasses, finer smaller twigs; the third level of construction composing the nest, is a small compression usually lined with fresh green leaves where the eggs are laid. Purple martins generally produce only a single brood. The average clutch size is 4 to 6 eggs per nest. Incubation lasts 15-16 days and the female is the main incubator, with some help from the male. Fledging, when the young leave the nest, occurs between 26-32 days after hatch day. The chicks will continue to receive care from both parents for up to a month after fledging and become reproductively mature at 1 year of age.

## Population

### Population threats

Purple martins suffered a severe population crash in the 20th century that was caused by the release and spread of European starlings in North America. European starlings and house sparrows compete with martins for nest cavities; they also kill adult martins, take over the nest and remove eggs or remaining young. Where Purple martins once gathered by the thousands, by the 1980s they had all but disappeared. Today, these birds are experiencing a unique threat to their long-term survival. Nearly all eastern species exclusively nest in artificial gourds and ‘condo’ units provided by human ‘landlords’. A practice that has been experiencing a steady decline in the number of ‘landlords’ offering nesting sites. One study found that nearly 90% of landlords were 50 years of age or older, and that younger generations were not exhibiting the same enthusiasm nor possess the resources to provided martin housing for the species.

### Population number

According to the What Bird resource, the total population size of the Purple martin is 11,000,000 individuals. According to the All About Birds resource the total population size of the species is 7 million birds. Overall, currently, Purple martins are classified as Least Concern (LC) on the IUCN Red List and their numbers today remain stable.

### Ecological niche

Purple martins feed mainly on various insects and play an important role as pest controllers. Thee birds also serve as food items for local predators such as hawks, starlings, owls, gulls, crows, snakes, raccoons, herons, squirrels, and house cats.

## Fun Facts

The current genus name of the Purple martin refers to Procne (Πρόκνη), a mythological girl who was turned into a swallow to save her from her husband. The word 'subis' is Latin and refers to a type of bird that breaks eagles’ eggs; it may have been applied to Purple martins because of their aggression towards birds of prey when martins are nesting.

Purple martins are known for their speed, agility, and their characteristic mix of rapid flapping and gliding flight pattern. When approaching their nesting site, these birds will dive from the sky at great speeds with their wings tucked.

Purple martins are considered synanthropic, meaning they have developed an association with humans over time and benefit from living in close proximity to them. Eastern populations have made a complete transition from nesting in the wild to relying on human-provided nesting sites. Martins have a very strong "site tenacity" and if they are successful in raising a brood, they will often return to the same site to nest year after year.

Purple martins may eat 400 flies in a day; they are also fond of fire ants which may make up a significant portion of their diet.

Purple martins are real acrobats in flight; they not only catch their food on the wing, but they also drink that way too. They skim the surface of the water and collect it with their lower bill.