Purple Martin Colony 2013
The Six baby martins are preparing to leave the nest. The camera view is now poor due to the feather dust and wax that comes off the feathers as they open up. The dust sticks to the camera lens. We can no longer clean the lens as disturbing the nest now could cause the babies to jump out prematurely.
Be sure to scroll down for information about Purple Martins.
Purple Martin (Progne subis)
The Purple Martin is the largest member of the swallow family in North America. It is approximately 7-8 inches in length. Adult males (which exhibit adult plumage typically after two years of age) are uniformly dark in color – with its wings and tail dark black and the remainder of the body feathers showing an iridescent purplish-blue black color. Adult females are noticeably lighter in appearance. The females exhibit a grayish breast, neck and forehead with whitish colored feathers on her stomach (belly). Similar to the male, she also has black wing and tail feathers and iridescent purplish blue-black feathers on her back and shoulders (although much less conspicuous). The under tail covert feathers on the adult female also help to distinguish her from sub-adult females because they are generally white with gray centers. Sub-adult females (which are females that are approximately one year old) look very similar to adult females except the under tail covert feathers are typically all white in color. The sub-adult females exhibit less iridescence on the back and shoulders as well. Sub-adult males also look similar to the sub-adult females except they usually have a darker throat and blotches of dark purplish black feathers on its breast, stomach and often under its tail (covert feathers).
Purple Martins feed almost entirely on flying insects that they capture on the wing. Martins are often touted as eating thousands of mosquitoes. Although they will eat mosquitoes, this is somewhat of a myth, as Purple Martins are generally active (searching for food) during the daylight hours and mosquitoes are typically most active during evening hours. Additionally, Martins often feed at higher altitudes (generally several hundred feet in the air) than mosquitoes would typically be found. The types of insects that Martins also eat includes bees, wasps, flies, dragonflies, beetles and just about any other insect that they can capture.
There are three subspecies of Purple Martins found in North America. The Eastern subspecies Progne subis subis which is generally found east of the Rocky Mountains as far north as Alberta (northwestern range) and Nova Scotia (northeastern range), Canada. The Western subspecies Progne subis arboricola is found primarily along the western coast and mountains as far north as British Columbia and southern Alaska. The desert southwest hosts the third subspecies, Progne subis hesparia.
Purple Martins are colonial birds’ which means that they typically nest in colonies. When the Martins return to North America from their wintering grounds in South America, the males will establish a territory that usually comprises one or more nest chambers depending on the type and design of housing that is offered. Once a territory is established, a male will defend it against other males and will sing in an attempt to attract a female. Once pairs are formed, the pair will roost together at night in the cavity they have selected. Nest building begins within a few days to several weeks later. Both the male and female participate in construction of the nest, although the female typically does most of the work. Throughout this period of time the male Purple Martin performs a vocalization that is known as “dawn-song”. Dawn-song is performed by male Martins during the pre-dawn and early morning hours of the day. This vocalization is believed to serve as a mechanism to attract other Martins to the colony site, particularly sub-adult birds that typically arrive at the breeding grounds four to six weeks after the adult birds have returned during spring migration. The males usually perform dawn-song while flying (often hundreds of feet) above the colony site. There are numerous other vocalizations that Martins perform however, there are two other sounds that are commonly heard at the colony site, the first is a “cheer-cheer” sound and the other is a “zweet” sound. The “cheer-cheer” song is often associated with the greeting of other Martins at the colony site, and the “zweet” call is a warning or alarm signal and is usually indicative of a predator in the area.
The incubation period (the amount of time it takes for the eggs to hatch) for Purple Martins is approximately 15 days. Eggs are laid typically one per day, generally in the early morning hours and the size of the clutch is between 3-8 eggs, with the average size clutch being 5 eggs. The eggs are pure white in color and are approximately one inch long by 5/8 of an inch wide. Incubation is done by the female via her brood patch which is a portion of her belly where she molts (loses) her feathers which allows for the heat generated by her body to be transferred to the eggs and the development of the embryos. Incubation usually starts the day before the last egg is laid. The eggs in the clutch typically hatch within approximately two days of each other and in some instances the eggs may all hatch within the same day. One additional interesting observation associated with the Martins is that they will bring green leaves to the nest during the time period when the female is laying eggs through incubation. The collection of green leaves is a behavior exhibited primarily by male Martins (although the female will also add green leaves to the nest). There are several theories as to the purpose of the addition of green leaves. One possibility is that the leaves serve as a natural pesticide by off-gassing a chemical known as hydrocyanic acid. Another possibility is that the green leaves contain moisture that helps to control the temperature/humidity in the nest cavity.
Once the eggs hatch, the young Martins remain in the nest for approximately 28 days, which is one of the longest nestling periods of any songbird in North America. Most songbirds fledge from the nest within approximately two weeks from the time of hatching. During this time the nestling are cared for by the adult Purple Martins. When the martins hatch they are pink in color and have no feathers. The female Martin will brood her young until the nestling birds are approximately two weeks of age and have developed enough feathers to help maintain their own body temperature. The baby Martins are blind when they hatch and remain that way until the young are approximately 6-7 days old when they begin to partially open their eyes. By about day 10 or 11, the eyes are completely open. Until the Martins are about two weeks old, one parent typically remains in the nest while the other parent is out collecting insects to feed the young. When the parent that is collecting food returns to the nest, the other parent will leave the nest and switch roles. As the young Martins get older the demand for food increases and both parents must be collecting food in order to feed the voracious appetites of their young. Research has shown that the weight of the young Purple Martin peaks at about 20-21 days of age and that it actually exceeds the weight of the adult Martins. Young Martins can fledge the nest from about 25 days of age but typically remain in the nest until about 28 days of age. It should be noted that the may remain in the nest as long as 32 days. It is not uncommon for a brood of Martins to fledge over a several day period. During this time the young that have already fledged will come and go from the nest along with the parents. Once the young Martins fledge, they will return to the colony site to roost at night with the adult birds for up to two weeks after fledging.
It is believed that man has “managed” Purple Martins longer than any other species of wild bird in North America. This relationship extends thousands of years back to Native Americans who attracted Martins to dried-out gourds. From there, colonists did the same and built wood houses for the Martins and this relationship and fascination with the Purple Martin has continued to grow. Over the course of time as the relationship was formed, the Purple Martin has undergone what is called a behavioral tradition shift. This means that the Martins have adapted or learned that nesting in close proximity to man is beneficial to them. Today virtually all Martins nesting east of the Rocky Mountains nest in man-made offered housing.
Predators include snakes, owls and hawks, raccoons, squirrels and cats. Most of these predators can be controlled by providing appropriate predator guards and offering well designed Martin housing which is discussed in more detail below. One of the biggest threats to the success of Purple Martins is the management of two non-native species of cavity nesting birds. These species are the English House Sparrow and the European Starling. Both of these species of birds not only compete with the Purple Martin for nest sites/cavities but will also kill Purple Martins by attacking them in a nest cavity, pecking and destroying their eggs and young and even the adult birds. These two species of birds are not protected by federal or state law and must be controlled and not allowed to nest at your colony site.
It is extremely important that anyone interested in trying to attract Purple Martins, use properly designed housing. Housing (whether it is built or purchased commercially) should be designed so that it can be managed carefully in order to ensure the success of the Purple Martins that use the housing. This means that the housing should be able to be raised and lowered from its pole vertically. Housing that can not be safely raised and lowered with out tipping or tilting the house should not be used or should be modified to allow for proper management. This is generally accomplished by using a winch or pulley system of some sort or perhaps a telescoping pole. Housing should be designed with individual nest compartments that measure at least 12 inches deep by 6 inches wide and 6 inches high. If gourds are used, they should be large gourds with a 10 inch diameter. Unfortunately many Purple Martin houses that are available commercially are designed with inadequate sized compartments (typically 6-inch cubes or less). Keep in mind that the size of an adult Purple Martin is between 7-8 inches. Additionally, the house should be mounted on a pole that is at least 10 – 12 feet above the ground and should be designed so that the orientation can not change or turn in the wind. Housing should also include a predator pole guard which is designed to keep climbing predators from reaching the house and the house itself should have the deeper nest compartments and owl/hawk guards which prevent them from reaching into the nest chamber and pulling out the Martins.
Today, most Purple Martins that are found east of the Rockies depend entirely on man-made housing for nesting. It is very important to understand that if you decide that you are interested in trying to establish a Purple Martin colony and become what is commonly referred to as a Purple Martin “landlord”, that it comes with a responsibility to properly manage your colony. Types of housing include multi-unit “apartments” as well as gourds. Martin housing is available commercially in both forms (as multi-unit structures as well as both natural and “artificial” gourds), that has been designed to allow for easy access to not only clean, but to inspect/manage during the nesting season. Management of a Martin colony primarily consists of monitoring your colony by performing nest checks. These nest checks allow the landlord to identify potential problems which could result in the loss of young or even the success of the entire colony. Potential problems could include infestation of parasites such as blowfly larvae, avian mites, lice, and ticks
Once the young Purple Martins have fledged, the Martins congregate in large pre-migratory flocks. Some of these flocks can amass Purple Martins that number in the hundreds of thousands. Observations have revealed that other species of swallows will also roost with the Purple Martins in these pre-migratory flocks. Purple Martins migrate to South America where they winter. It is believed that most Martins winter in Brazil and Bolivia and there are reports that some of the roosts may number in excess of one million birds. These South American winter roosts often include other species of Martins (including the Gray-breasted Martin and Brown-chested Martin) that are found in South America. It is believed that most Martins leave North America by late October, and based on the research that has been done, the first Martins to return to North America (known as “scouts”) appear in southern Florida within approximately the first week of January. These Martins are birds that breed in the southern range of the Purple Martin’s breeding area. Spring migration continues into the northern breeding range of the Martin through the month of June. Typically the last migrants to return to the breeding grounds are the sub-adult birds.