OR/WA BLM and FS Region 6 Units where Suspected or Documented:
Both the Forest Service and BLM have listed the purple martin as a Sensitive Species/Special Status Species in Oregon.
The purple martin has been documented or is suspected of occurring on four National Forests (FWI, SIU, UMP, WIL), one Scenic Area (CRG) and five BLM districts in Oregon (CB, EU, MD, RO, SA).
Natural Heritage Program Rank and Status:
Oregon State Rank: S2B; breeding population imperiled in Oregon.
Washington State Rank: S3B; breeding population rare or uncommon.
National Rank: N5B; breeding population common and widespread.
Global Rank: G5; widespread, abundant, and secure through its range.
Oregon State Status: SC; sensitive critical.
Washington State Status: C; candidate for listing; currently under review.
SOC; species of concern; an unofficial status, the species appears to be in jeopardy, but insufficient information to support listing.
Figure 1. NatureServe map of the conservation status of the purple martin in the United States and Canada. A species is not shown in a jurisdiction if it is not known to breed in the jurisdiction or if it occurs only accidentally or casually in the jurisdiction. Thus, the species may occur in a jurisdiction as a seasonal non-breeding resident or as a migratory transient but this will not be indicated on this map. Natureserve 2007.
Purple martins are the largest member of the swallow family in North America. Three races (subspecies) are recognized: (1)Progne subis subis being a lowland, highly colonial nester breeding in eastern North America and eastern Mexico, (2) Progne subis hesperia breeding in the deserts of Arizona , western Mexico, and Baja California, and (3) Progne subis arboricola being primarily solitary (occasionally loosely colonial) nesters in montane aspen forests as well as breeding along the Pacific coast of the United States and Canada, and in the Rocky Mountains (Brown 1997, Purple Martin Conservation Association (PMCA) 2006, Wiggins 2005). There remains considerable uncertainty regarding the relationship of the Pacific Northwest, Rocky Mountain, and southwestern desert forms (Brown 1997).
It is 178-203mm in length, weighing about 50g. The plumage of adult males is a glossy dark purple, usually appearing black. Females have gray upperparts with some purple coloration, whitish underparts, some speckling on the sides, with a gray breast band and throat. The head, nape and rump tend to be slightly darker. Both sexes have a forked tail (Gough et al 1998, PMCA 2006, Sauer and Droege 1992).
In their first year, males resemble females but often show some purple coloration. The subadult plumage of one-year and older male and females is distinct enough that they can be distinguished from each other, and also from the plumages of the adult males and females. Because of this, breeding martins have four distinct sex and age classes during the breeding season; (1) adult male, (2) adult female, (3) subadult male, and (4) subadult female. After nestlings fledge and join the population, they become a fifth sex/age class, as juveniles cannot be sexed by plumage differences (PMCA 2006).
In flight they resemble the European starling, but with a forked tail and longer wings. They fly like typical swallows with short glides alternating with very rapid flapping (National Geographic 1999).
In addition to plumage differences, martins can also be sexed by their behaviors. One of the easiest ways to tell all breeding-age males (both adult and subadult) from females is by their song. Only male martins sing the extremely common song that ends with a rapidly clicking, "krieeek" sound (PMCA 2006).
The male purple martin is easily told from other swallows by its entirely dark plumage. It is vaguely similar to the starling but has a smaller bill, longer wings and a darker plumage. Female purple martins are similar to bank and northern rough-winged swallows but are larger, and flap more slowly. At close range, the darker upperparts of the martin are evident (Gough et al 1998).
Purple martins are neotropical migrants, spending the non-breeding season in Brazil and migrating to North America to nest (Gough et al 1998, PMCA 2006).
The purple martin migrates mainly along the coast. It arrives in the southern U.S. by early February and northern states and southern Canada in April (Morton and Derrickson 1990). It migrates through Costa Rica from August to mid-October and late January-April (Stiles and Skutch 1989). It is present in South America mostly September-March (Ridgely and Tudor 1989).
In earlier times their breeding was presumably dependent upon the presence of available tree cavities that served as nest sites. Today, however, they nest almost exclusively in artificial nest boxes (Finlay 1971). East of the Rockies purple martins are colonial nesters and are totally dependent on human-supplied housing (PMCA 2001). West of the Rockies and in the deserts they largely nest in their ancestral ways, in abandoned woodpecker nest cavities (PMCA 2006) located in the mid-story of the canopy (Gough et al 1998). In the Pacific Northwest, purple martins are beginning to use gourds and clusters of single-unit boxes for nesting (PMCA 2006).
At natural sites, they breed in single pairs or small groups. East of the Rockies they usually nest in colonies (Sauer and Droege 1992). Colony size in the eastern portions of the range depends on the number of the nesting cavities available. In human-supplied structures, colony size is typically less than 12 pairs, but much larger colonies can form at sites with large martin “apartments” (Brown 1997). Once established at a nest location, martins usually come back every year to the same site (Thomson 2001). Males compete for nest sites within the colony. Females are also known to fight over nest sites. The larger the colony, the more the birds fight over territory. Although birds in colonies face increased risk of parasites and increased competition for resources, reproductive success is not highly dependent on colony size (Copley et al. 1999, Davis and Brown 1999, PMCA 2001, Russell and Gauthreaux 1999). Both male and female purple martins typically breed first as one-year old subadults (Wiggins 2005).
The pair bond of the purple martin is monogamous. The male and female cooperate equally in building the nest out of mud, grass and twigs (PMCA 2006, Thomson 2001). Observations indicate that most nest building takes place in the morning; the birds are not generally around the colony in the afternoon (Finlay 1971).
The female lays from two to eight (usually 4-5; Sauer and Droege 1992)pure-white eggs at a rate of one egg per day (Gough et al 1998, Thomson 2001, PMCA 2006). Eggs are usually laid in the early morning on successive days (Allen and Nice, 1952). Female martins mated to adult males began laying eggs up to two weeks before those mated to yearling males (Finlay 1971).
The female incubates the clutch for approximately fifteen days (Gough et al 1998, PMCA 2006, Sauer and Droege 1992, Thomson 2001). Males guard the nest when females go off to feed (Sauer and Droege 1992).
Both parents feed the young for a period of 26-32 days until the young fledge. The young continue to be dependent on their parents for food and training for an additional one to two weeks after fledging during which time they learn to forage by following the parents (Copley et al. 1999, Davis and Brown 1999, PMCA 2006, Russell and Gauthreaux 1999). It's not uncommon for the fledglings to return to their human-supplied housing at night to sleep during this period (PMCA 2006, Sauer and Droege 1992).
There are usually one, but sometimes two broods per season; on rare occasions there will be three (Ehrlich et al 1988, Gough et al 1998, Sauer and Droege 1992). Depending on the location, a few or many of the breeding males may be subadults (Finlay 1971, Sauer and Droege 1992). Most individuals breed for two to three seasons (Sauer and Droege 1992).
Purple Martins, like all swallows, are aerial insectivores (PMCA 2006). Martins are extremely agile and fast fliers, normally flying at 45 mph or more, which aids them in their quest for food (PMCA 2001). Compared to most other swallow species, martins feed at relatively high altitudes (50 to150 m), moving to relatively low altitudes and closer to their nest sites later in the day (Brown 1997). They feed exclusively on flying insects while foraging over fields, water, or marshes (Gough et al 1998, PMCA 2006, Sauer and Droege 1992). Martins catch insects in flight although they occasionally forage by walking along the ground (Sauer and Droege 1992). Purple martins have a diverse diet that includes a wide range of flying insects such as dragonflies, damselflies, grasshoppers, moths, wasps, beetles, bees, junebugs, flying ants, butterflies, and others (Gough et al 1998, PMCA 2001, PMCA 2006, Sauer and Droege 1992).
They do not eat mosquitoes as some believe and is often claimed by companies that manufacture martin housing. An intensive seven year diet study conducted at PMCA headquarters in Edinboro, PA failed to find a single mosquito among the 500 diet samples collected from parent martins bringing beakfuls of insects to their young. The samples were collected from martins during all hours of the day, all season long, and in numerous habitats, including mosquito-infested ones. Purple martins and freshwater mosquitoes rarely ever cross paths. Martins are daytime feeders, and feed high in the sky; mosquitoes, on the other hand, stay low in damp places during daylight hours, or only come out at night (PMCA 2006).
After the chicks fledge, purple martins begin to form large roosting flocks at night after the nesting season and before their southward migration (Russell and Gauthreaux 1999, Sauer and Droege 1992). From late June to early September, martins often congregate in pre-migratory roosts that may contain up to one hundred thousand birds or more. Usually all members leave the roost in early morning to feed and return again in the evening. Earlier in the summer, birds normally depart from the roost in all directions for feeding purposes. Later in the summer the departures turn southward as migration begins. Martins are willing to travel far for food, often traveling 80-100 kilometers from the roost daily. They often follow specific flight corridors when returning to the roost (Russell and Gauthreaux 1999).
Range, Distribution, and Abundance:
The Purple Martin can be found throughout nearly the entire United States east of the Rocky Mountains. Although declining in many western states, it is also found in isolated areas in Canada, Oregon, Washington, California, Utah, Colorado, Arizona, New Mexico and Mexico. The bird is an early spring migrant returning from its winter grounds in South America (National Geographic 1999).
Figure 2. Range depicted for New World only. The scale of the maps may cause narrow coastal ranges or ranges on small islands not to appear. Not all vagrant or small disjunct occurrences are depicted. For migratory birds, some individuals occur outside of the passage migrant range depicted. NatureServe 2007. Data provided by NatureServe in collaboration with Robert Ridgely, James Zook, The Nature Conservancy - Migratory Bird Program, Conservation International - CABS, World Wildlife Fund - US, and Environment Canada - WILDSPACE
Martin populations in the Rocky Mountains, the desert southwest, and particularly the Pacific Northwest have been poorly studied (Wiggins 2005). Where they do occur, they are not as abundant as in the eastern United States (Figure 3).
Figure 3. These maps indicate the number of birds seen on BBS routes, grouped into convenient categories of relative abundance. The maps predict the average number of birds of the species that could be seen in about 2.5 hours of birdwatching along roadsides (by very good birders). They are based on mean counts on BBS routes over the interval 1994 - 2003. . BBS info from http://pick4.pick.uga.edu/mp/20q?go=http://www.mbr-pwrc.usgs.gov/bbs/ Surveys conducted by the Oregon Department of Fish and Wildlife in 1998 documented 784 pairs and 112 colonies1 in Oregon (ODFW 1999). Colony sizes ranged from 1-55 pairs (11 pair average). The abundance of the birds were considered uncommon or local. This species was not detected in Clackamas, Marion, Jackson, Josephine, Washington and Yamhill Counties. They concluded that the breeding range is smaller than it was in 1940. Purple martins were “lacking” in Klamath and Jackson Counties, where they formerly were known to nest.
According to the Washington Department of Fish and Wildlife, purple martins in Washington occur primarily along the shorelines of Puget Sound, the northern shores of the Olympic Peninsula, Grays Harbor, Long Beach and extend up the Columbia River for 150-175 miles (WDFW 2003).
Figure 4. A compilation of purple martin observation data from GeoBob, NRIS fauna, ORNHIC and miscellaneous observations.
Based on data collected from the North American Breeding Bird Survey (BBS), there was a significant population increase in central North America between 1966-1988, and a significant population increase in western North America between 1978-1988 (Sauer and Droege 1992). The western population had been experiencing decreases due to starling competition for nest sites; house sparrows also may take over martin nest cavities (Natureserve 2007).
Figure 5. This map provides a best guess of population change for the species over its North American range. Areas of increase are blue, and areas of decline are red. Areas where there is no apparent trend, or where we do not have enough information to say that a trend exists, are also indicated. Note that these maps are supposed to provide a general view of population change for the long-term. They do not provide much insight into short-term changes within the 1966 - 2003 period. . BBS info from http://pick4.pick.uga.edu/mp/20q?go=http://www.mbr-pwrc.usgs.gov/bbs/ Habitat Associations:
Purple martin is an aerial feeder that utilizes a wide variety of terrestrial habitats including cropland, hedgerow, desert, grasslands, savanna, shrubland, chaparral, suburban, orchard, conifer woodland and hardwood woodlands. Generally, they inhabit open areas and prefer an open water source nearby. They often drink and bathe while skimming over open water. Having water nearby also helps support plentiful insects for food (PMCA 2001). Martins adapt well in and around people, but are out-competed by starlings and sparrows in urban areas.
They nest in tree cavities, abandoned woodpecker holes (including those in saguaro cacti), and crevices in rocks. In areas that lack natural nesting habitat, bird-houses and hollow gourds put up by humans are often used for nesting (Sauer and Droege 1992). In Oregon, purple martins typically nested in dead Jeffrey pine (Pinus jeffreyi) or spruce, but also in building crevices and more recently in nest boxes and under bridges (Gabrielson and Jewitt 1940, Marshall et al. 2003). A recent study by Horvath (2000) in Oregon found that purple martins nested primarily over water, in nest boxes, gourds, pilings, and snags. In rural areas in Washington, martins nest at low-elevation coastal sites, utilizing wood pilings over water and occasionally holes in trees (Smith et al. 1997). Similar sites are used in south coastal British Columbia, but nest boxes have become an increasingly important resource there and are apparently responsible for maintaining local populations of martins (Campbell et al. 1997). In eastern North America, purple martins historically nested along forest edges and clearings, especially near areas of water (Brown 1997, Ducey 2000). Nest sites included holes in trees as well as niches on cliffs. At some point in the past 300 years, eastern martin populations began nesting in man-made structures and are now restricted to breeding in martin houses, gourds (erected by humans), holes in buildings, or niches in traffic lights and street lamps (Brown 1997). Early reports suggest that eastern martin populations began their nest-site shift before European colonization; Catesby (1731) noted martins utilizing hollowed-out gourds erected by Native Americans in the southeastern United States in the early 1700s.
Historically, purple martins were thought to forage around their nesting sites (Brown 1997). The situation in eastern North America today is very different (Wiggins (2005). Although martin foraging habitat still appears to depend on the locality of suitable nesting sites, such sites are now typically suburban areas or even heavily populated cities. Purple martins (the hesperia subspecies) in the desert Southwest may feed far from their nesting sites over habitat in which they do not nest (Phillips et al. 1964, Brown 1997).
The attraction to areas of open water may relate to a number of nesting and foraging factors: 1) the presence of partially submerged, dead trees with nesting cavities, 2) a reliable source of insect prey such as dragonflies and damselflies as well as ephemeral blooms of other aquatic insects (e.g., Chironomidae), and 3) importance as a foraging area early in the season or at high altitudes, when cold temperatures often drive martins to feed low over the water (Riggs 1947, Brown 1997).
The biggest factors limiting populations are the availability of and competition for nest sites, especially with European starlings (Wiggins 2005). Populations of Purple Martins have declined in many areas for two main reasons; (1) the reduction of natural cavities (e.g., hollow trees, snags) from human activities (e.g., logging), and (2) competition for nest sites from invasive species such as the English sparrow and European starling (PMCA 2001).
In the Pacific Northwest, where martins still nest in tree cavities, competition from starlings can lead to local extirpation, as has happened in coastal areas of Oregon (Horvath 2000). At established colony sites, house sparrows and starlings will fight with martins, kill their nestlings, and/or break eggs. Allowing house sparrows and starlings to nest in martin housing will significantly reduce martin occupancy and productivity (PMCA 2006
Land management activities that affect hydrological processes may have significant consequences for martin populations, including changes in water flow from activities such as road building, timber harvesting, and livestock grazing. Alterations in local water flow and retention may lead to decreased insect abundance and thus poor reproductive success by purple martins (Wiggins 2005).
Brown (1997) noted the potential for pesticide ingestion by purple martins on wintering grounds in Brazil, but there have been no studies of pesticide accumulations to determine if this is indeed the case.
The most commonly noted cause of mortality is exposure to adverse weather conditions (Wiggins 2005). Since purple martins feed only on flying insects, spring and summer populations are extremely vulnerable to starvation and are periodically decimated during extended periods of cool and/or rainy weather and the resultant lack of insect food. Bad weather that persists for three or more days in a row is often lethal causing high casualties of purple martins (PMCA 2006, Sauer and Droege 1992).
Martins are also susceptible to human interference on their wintering grounds, as they often stage and roost in large flocks within urban areas (Hill 1988).
Purple martins are protected by The Migratory Bird Treaty Act. Currently, there are no published management plans or conservation strategies for purple martins (Wiggins 2005). However, there is a network of concerned volunteers, coordinated by the Purple Martin Conservation Association (PMCA; www.purplemartin.org), that promotes continent-wide interest in improving conditions for purple martins, primarily nesting conditions. The PMCA web site provides a wealth of information on all aspects of martin biology (Wiggins 2005).
Although not designed as a range-wide or even a regional management plan, state-based Partners in Flight (PIF) management recommendations for purple martin are currently the only published frameworks from which regional plans could be constructed (Wiggins 2005). The purple martin is a focal species for open water and snags. PIF recommendations and management suggestions for the purple martin from the Conservation Strategy for Landbirds in Lowlands and Valleys of Western Oregon and Washington (Altman 2000) include the following:
Where ecologically appropriate and where European starling and house sparrow presence is minimal, initiate the following actions within or adjacent to open water:
retain old pilings for potential use as nest sites
retain or create >1.2 snags/ha (3/ac) >30 cm (12 in) dbh and >6 m (20 ft) high (above water)
use nest boxes as short-term management until natural cavities are available
open air space and easy access to cavities (i.e., no physical obstructions within 10m)
Increase population of purple martins to >1,000 pairs (includes non-water nesting birds) in the next 10 years (by 2010) through expansion of existing colonies and establishment of new colonies.
All attempts to establish colonies should consider the European starling population in the area.
Avoid applying insecticides within 12 km (7.5 m) of nesting colonies (Rodrick and Milner 1991).
Where there is open water, the important condition for landbirds is the presence of snags for nesting cavities and colony establishment (Altman 2000). Purple martins also depend on healthy populations of primary cavity constructors such as flickers and woodpeckers to create their nesting sites. Open, wet meadows are particularly important as martin foraging areas. Maintaining the integrity (vegetative composition as well as water flow) of existing meadows, as well as creating new wet meadow habitat (e.g., via fire disturbance) would provide long-term habitat sustainability for purple martins (Wiggins 2005).
Traditionally, forest management guidelines recognize snags as important nest trees for martins and other secondary cavity nesting species. However, Gillihan and Levad (2002) found that 71 of 80 purple martin nests in western Colorado were in live trees. They also suggested that current, widespread fire suppression policies within western forests may be negatively affecting purple martins. Reducing or eliminating wildfire as a natural disturbance results in the loss of potential nesting habitat, as snag recruitment is severely curtailed.
For land managers in western montane forests, providing adequate stands of mature aspen is the key management practice that will support viable populations of purple martins. However, it is also critical to maintain patches of open, wet meadow habitat as foraging habitat since such sites are strongly preferred by breeding martins (Gillihan and Levad 2002). As mentioned earlier, long-term land management policies (e.g., relaxed fire suppression) that promote aspen regeneration, open habitats, and natural water flow regimes will ensure the sustainability of preferred purple martin habitats.
Data are needed on all aspects of nesting ecology and habitat relationships. Horvath (2000) found that the dependence of Oregon martins on man-made structures appeared to be due, at least partly, to competitive exclusion from natural nest holes by European starlings. In coastal areas, starlings have taken over many of the nest sites historically used by purple martins. Martins breeding inland, however, faced almost no competition from starlings and utilized snags as their primary nesting substrate. These observations suggest that western populations of purple martins should be monitored, with special attention paid to any apparent displacements by European starlings. To reduce this potential displacement, purple martin nest boxes now often incorporate European starling-resistant entrance holes (Kostka 2001). Should native bird species (e.g., tree swallows, bluebirds) try to take over empty martin housing, the entrance holes can be temporarily plugged and appropriate, single-unit housing can be placed elsewhere. Once native birds have accepted the new housing, the martin housing can be reopened. Martin housing should be stored inside for the winter (or closed up) to keep paper wasps, squirrels, and other birds from claiming the house before martins return (PMCA 2006).
Other pertinent information (references to Survey Protocols, etc):
Populations have been augmented by nest boxes in some areas. Over one million people in the United States have erected nest boxes for purple martins. To successfully attract martins, the nest box must be placed in an open area and periodically checked for invasive species. Because purple martins nest later than most other bird species, it has been suggested that martin houses be erected late in the season (timing dependent on latitude) so that these man-made cavities become available when martins are ready to begin nesting. This also reduces the likelihood that martins would be competing with other species for these cavities at that time. Many people enjoy watching the spectacular agility of martins in flight, as well as listening to their song. Insect control benefits also prompt landowners to erect nest sites for purple martins (PMCA 2001, Copley et al. 1999).
Theresa Stone, Umpqua National Forest, Roseburg OR
14 September 2007 Updated:
May 2009, by Rob Huff, Oregon State Office, BLM
(Update modified the list of Forest Service and BLM field units that consider this species to be suspected or documented; also, updated species FS and BLM status in Washington (no status, not sensitive)).
References: Allen, R. A., M. M. Nice. 1952. A study of the breeding biology of the purple martin (Progne subis). Amer. Midl. Nat., 47:606-665.
Altman, B. March 2000. Conservation strategy for landbirds in lowlands and valleys of Western Oregon and Washington. Oregon/Washington Partners in Flight. Version 1.0.
Bowditch, J. 1990. A way to stop crow and owl predation at purple martin houses. Purple Martin Update 2(3):8-9.
Brown, C.R. 1997. Purple Martin (Progne subis). In: A. Poole and F. Gill, editors. The birds of North America. No. 287. The Academy of Natural Sciences and the American Ornithologists’ Union, Philadelphia, PA and Washington, D.C.
Campbell, R.W., N.K. Dawe, I. McTaggart-Cowan, J.M. Cooper, G.W. Kaiser, and M.C.E. McNall. 1997. The birds of British Columbia. Vol. 3. Royal British Columbia Museum, Victoria, British Columbia, Canada.
Catesby, M.R. 1731. The natural history of Carolina, Florida and the Bahama Islands. London, U.K.
Coates Manufacturing, "Purple Martin Information" (on-line). Accessed 10/22/00 at http://coatesmfg.com/info.html.
Copley, D., J. Finlay, D. Fraser. 1999. Purple Martins (Progne subis): A British Columbian Success Story. Canadian Field-Naturalist: 226-229.
Davis, J., C. Brown. November 1999. Costs of coloniality and the effect of colony size on reproductive success in Purple Martins. The Condor, 101: 737-745.
Ducey, J.E. 2000. Birds of the untamed west: The history of birdlife in Nebraska, 1750 to 1875. Making History, Omaha, NE.
Ehrlich, P., Dobkin, D., and Wheye, D. (1988). The birders handbook: A field guide to the natural history of North American birds. New York: Simon and Schuster Inc.
Finlay, J.C. 1971. Breeding biology of purple martins at the northern limit of their range. Wilson Bulletin 83:255-269
Gabrielson, I. N. and S. G. Jewett. 1940. Birds of Oregon. Oregon State College, Corvallis, OR.
Gillihan, S. and R. Levad. 2002. Tree-nesting purple martins in the Colorado Rockies. Purple Martin Update 11:4-7.
Ginaven, J. 1990. Using decoys to attract purple martins. Purple Martin Update 2(3):26-27.
Gough, G.A., Sauer, J.R., Iliff, M. Patuxent Bird Identification Infocenter. 1998. Version 97.1. Patuxent Wildlife Research Center, Laurel, MD. http://www.mbr-pwrc.usgs.gov/id/framlst/infocenter.html
Oregon Natural Heritage Information Center (ORNHIC): http://oregonstate.edu/ornhic/ Hill, J.R. III. 1988. A tale of two cities: the purple martin on its Brazilian wintering grounds. Purple Martin Update 1:1-5.
Horvath, E. 1999. Distribution, abundance, and nest-site characteristics of purple martins in Oregon. Oreg. Dept. Fish and Wildl. Wildl. Diversity Prog. Tech. Rept. 99-1-01.
Horvath, E. 2000. Distribution, abundance, and nest site characteristics of purple martins in Oregon. Oregon Birds 26:115-122.
Kostka, K. 2001. A revolutionary new entrance hole design: Duke Snyder’s starling excluder. Purple Martin Update 10:8-10.
Marshall, D.B., M.G. Hunter, and A.L. Contreras. 2003. Birds of Oregon. Oregon State University Press, Corvallis, OR.
Mitchell, W. A. 1988. Songbird nest boxes. Section 5.1.8, US Army Corps of engineers wildlife resources management manual. Tech. Rep. EL-88-19. Waterways Expt. Station, Vicksburg, Mississippi. 48 pp.
Morton, E. S., and K. C. Derrickson. 1990. The biological significance of age-specific return schedules in breeding purple martins. Condor 92:1040-1050.
National Geographic Society, 1999. Field guide to the birds of North America Third Edition. Washington, D.C.: National Geographic.
NatureServe. 2007. NatureServe Explorer: An online encyclopedia of life [web application]. Version 6.2. NatureServe, Arlington, Virginia. Available http://www.natureserve.org/explorer.
ODFW. 1999. Distribution, abundance and nest site characteristics of purple martins in Oregon. Report by E. Horvath.
Purple Martin Conservation Association (PMCA). 2006. The Purple Martin Conservation Association in cooperation with Edinboro University of Pennsylvania. http://www.purplemartin.org/
Ridgely, R. S. and G. Tudor. 1989. The birds of South America. Volume 1. University of Texas Press, Austin, USA. 516 pp.
Ridgely, R. S., T. F. Allnutt, T. Brooks, D. K. McNicol, D. W. Mehlman, B. E. Young, and J. R. Zook. 2005. Digital distribution maps of the birds of the western hemisphere, version 2.1. NatureServe, Arlington, Virginia, USA.
Phillips, A. R., J. Marshall, and G. Monson. 1964. The birds of Arizona. University of Arizona Press, Tucson, AZ.
Riggs, C.D. 1947. Purple Martins feeding on emerging may-flies. Wilson Bulletin 59:113-114.
Rodrick E. and R. Milner (tech. eds.). 1991. Management recommendations for Washington’s priority habitats and species. Wash. Dept. Fish and Wildl., Wildl. Manage., Fish Manage., and Habitat Manage. Divisions. Olympia.
Russell, K., S. Gauthreaux. September 1999. Spatial and temporal dynamics of a Purple Martin pre-migratory roost. The Wilson Bulletin, 111: 354-362.
Sauer, J.R., and S. Droege. 1992. Geographical patterns in population trends of Neotropical migrants in North America. Pages 26-42 in J.M. Hagan, III, and D.W. Johnston, editors. Ecology and conservation of Neotropical migrant landbirds. Smithsonian Institution Press, Washington, DC.
Sauer, J. R., J. E. Hines, and J. Fallon. 2005. The North American breeding bird survey, results and analysis 1966 - 2005. Version 6.2.2006. USGS Patuxent Wildlife Research Center , Laurel MD.
Smith, M.R., P.W. Mattocks, Jr., and K.M. Cassidy. 1997. Breeding birds of Washington State. Volume 4. In: K.M. Cassidy, C.E. Grue, M.R. Smith, and K.M. Dvornich, editors. Washington State Gap Analysis – Final Report. Seattle Audubon Society Publications in Zoology No. 1, Seattle, WA.
Stiles, F. G. and A. F. Skutch. 1989. A guide to the birds of Costa Rica. Cornell University Press, Ithaca, New York, USA. 511 pp.
Thomson, M. 2001. "Progne subis" (on-line), Animal Diversity Web. Accessed September 15, 2007 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Progne_subis.html.
Washington Natural Heritage Program: www.dnr.wa.gov/nhp/ WDFW. 2003. Purple martin (Progne subis). Priority habitat and species report, volume IV:birds.
Western Purple Martin Working Group. Interim population objective for the
Pacific population of the Western Purple Martin (Progne subis arboricola). Available from: Stan Kostka at firstname.lastname@example.org).
Wiggins, D. (2005, March 31). Purple Martin (Progne subis): a technical conservation assessment. [Online]. USDA Forest Service, Rocky Mountain Region. Available: http://www.fs.fed.us/r2/projects/scp/assessments/purplemartin.pdf [date of access].
Appendix 1. Western Purple Martin Working Group Interim Population Objective
Interim Population Objective for the Pacific Population of the Western Purple Martin
Western Purple Martin Working Group*,
Stan Kostka, Recording Secretary, email@example.com
Population Objective: Increase the Pacific Coast population of Western Purple Martin (Progne subis arboricola,
Behle 1968) in California, Oregon, Washington, and British Columbia to >6,000 pairs by