BC Purple Martin Stewardship and Recovery Program

NEW 2013! - Status Report on the Western Purple Martin in BC  -  see Recent Publications section below for citation

Purple Martins are the largest swallow in North America. The western subspecies (Progne subis arboricola), which occurs exclusively west of the Rocky Mountains from sw. BC to s. California (and is separate and genetically distinct from the eastern subspecies, P. s. subis), is Blue-listed in British Columbia and recovering from a severe population decline in the mid-late 1900s. Historically, Western Purple Martins nested in woodpecker holes in old trees or snags in open woodland areas or near freshwater and likely made extensive use of fire-killed stands - wildfire was originally a common forest renewal process in dry rain shadow areas throughout the Strait of Georgia and south into Puget Sound, WA. Due to timber harvest, fire prevention, snag removal, burned timber salvage and agricultural and urban development throughout their original breeding range on coastal lowlands around the Georgia Basin, this habitat type has been lost. Resident populations of non-native European Starlings and House Sparrows that became established in BC in the early-mid 1900s also provide strong competition for any remaining nest cavities (but are likely NOT the sole or primary cause of the decline).

As other suitable habitat was lost, martins shifted to nesting in woodpecker cavities in abundant old and decaying untreated wooden pilings remaining from early industrial development around the Strait of Georgia (as well as in Puget Sound, WA, and along the lower Columbia River), and as these old pilings fell or were replaced with creosote-treated pilings (and later steel and concrete pilings), in which woodpeckers cannot excavate nest cavities, their numbers steadily declined due to the slowly declining supply of usable nest cavity sites. By the early 1980s, when old untreated pilings were almost entirely gone, the BC population of Western Purple Martins was reduced to less than 10 known breeding pairs.

Since then, the British Columbia population of Purple Martins has rebounded to over 200 pairs by 2002,  650 pairs by 2007, 800 pairs by 2012 and 1,200 pairs by 2016-2018. This is due to the volunteer-based nest box program begun in the Georgia Basin area in 1986, as well as a similar program begun a decade earlier (1975) by conservation volunteers in Puget Sound, Washington.

This growth has not been continuous... After nearly two decades of gradual population increase since nest boxes were provided on marine pilings, the BC population increased dramatically between 2003 and 2006, due mainly to good weather conditions throughout the breeding season in these years, resulting in an ample food supply of flying insects for both adults and nestlings. As for other swallows, the nesting success and fledgling production of Purple Martins is highly sensitive to adverse (wet) weather-induced reduction in food supply availability, and yearling (subadult) recruitment and population growth or decline are highly dependent on reproductive success. An article about the history of the recovery of Purple Martins in BC, up to and including 2004, was printed in BirdWatch Canada (winter 2005 No. 30, p.21-22), a publication of Bird Studies Canada, and is available here in .PDF format.

After stalling for several years at 500-650 pairs (2006-10) due to low fledgling production and yearling (subadult) recruitment as a result of 4-5 nesting seasons with long cool wet periods that limited food availability and reduced nestling survival, the BC population again began to increase annually, reaching our initial interim target of 800 pairs in 2012 and 1,200 pairs in 2016, where growth has again stalled temporarily due to several years with cool wet periods in May-June, causing substantial (to 40-50%) nestling losses and low reproductive success, fledging production and resulting yearling recruitment.

Since 2002, GBEARS has provided overall co-coordination and scientific direction, monitoring and management of the BC Purple Martin Stewardship and Recovery Program. As part of this program, nest boxes are put up at potential new colony sites as well as existing ones. Each box is numbered with a unique number that includes the year of installation. Abundance, nesting success and production at each colony site are monitored and recorded.

Also, Western Purple Martin nestlings from each colony were banded with numbered bands which allow us to track their migratory routes, dispersal and recruitment and colony and nest box selection throughout their lives, without further capture or disturbance.  Bands read with spotting scopes in later years indicate that martins fledged from any one colony return to nest at many different colonies throughout the Strait of Georgia and Puget Sound, providing extensive genetic mixing within at least the BC and Puget Sound, WA, population, with occasional dispersal to the lower Columbia River Basin and possibly to Oregon and California.

In 2007 a 10-year old adult male banded in 1997 and a 9-year old adult female banded in 1998 were both identified from their band numbers and nested successfully. The female returned and nested successfully again in 2008 as a 10-year old bird. This female and a second previously unseen female returned and nested as 11-year old birds in 2009, but neither nest was successful and neither of these birds has been seen again since. These are believed to be western longevity records to date for males and females in the wild. Most martins that survive their first winter live only 2-3 years and relatively few (<10%) exceed 5 years of age.

In addition, this long term banding study provides valuable information on the population dynamics and variable age composition of the BC population, which is important for understanding changes in the rate of growth or decline of the population due to variations in nesting success, fledgling production and recruitment of new subadult birds, and thus the progress and overall success of the recovery program. (Some of these results may be applicable generally to other equally weather-dependent but less closely monitored swallow populations as well.) This long-term population dynamics and age composition study is unique for Purple Martins in Canada and for Western Purple Martins in western North America, and has been supported in part by the Canadian Wildlife Service, The Baillie Fund of Bird Studies Canada, The Canadian Wildlife Foundation and Timber West..

In 2005 and 2006 a survey of remaining historic and potential new freshwater nesting sites was conducted in preparation for re-introducing Western Purple Martins into naturally occurring nesting cavity situations in the wild. In general, suitable freshwater sites with snags for mounting a few "starter" nest boxes and containing natural cavities for new colonies to expand into as they grow were scarce, particularly on south Vancouver Is. and in the Lower Mainland. Many historic freshwater nesting sites have been lost to various forms of development, the snags have fallen or been removed (often most or all of the remaining snags are redcedar, which decay very slowly, so remain sound and stand intact for many decades but have few if any woodpecker cavities suitable for nesting) and very little suitable 'traditional' nesting habitat remains in the Georgia Basin.

So far 15 freshwater nest box sites have been established  in the Lower Mainland and lower Fraser Valley and 10 have been initiated on the east coast of Vancouver Island and the Gulf Islands, some on pilings and others on flooded snags (at left, Crofton Lake). Three of these sites were first occupied by Western Purple Martins in 2013, at Westwood Lake in Nanaimo and Comox Lake near Courtenay on east Vancouver Island, and at Burnaby lake in Vancouver on the BC Lower Mainland, and others have been occupied since. At several locations martins are nesting in cavities in old abandoned pilings left from earlier industrial activity, and they have begun using snag cavities in at least one location (Crofton Lake, right). We hope and expect to see this trend continue in future, with potential use of cavities in snags on upland sites when suitable habitat can be provided.

There are currently ~120 active colonies established - most active colony locations are shown in the following map (2018):

* Shaded area indicates historic breeding range of Purple Martin in BC; colonies in Puget Sound, WA, (dark grey) not shown. New nesting sites in the lower Fraser River valley east of Vancouver at Mission (2007-8, 2013-18) and Harrison Mills (2013-18) and in Johnstone Strait between Port Neville and Port McNeill (2013-18) also not shown.

Nest Box Construction and Mounting Plans

If you would like to build your own Western Purple Martin nest boxes, click here for the nest box plans and here for instructions on how to mount them. If you want copies of these document files, save them to a file on your computer and print them from that file. (Tip: If the drawings appear difficult to read, click on them to increase screen zoom magnification.) Please contact us before putting up nest boxes, so we can keep track of where they are and also provide any help or further information you might need.

When choosing suitable nest box locations for attracting Western Purple Martins, it's important to keep in mind that they like to nest in clusters of single boxes, usually placed in open spaces beside or over water (rather than the familiar multi-compartment "condos" placed over land for the eastern subspecies). In BC eastern martin apartment houses are NOT accepted by western martins and tend to be taken over by non-native European Starlings and House Sparrows, which then exclude martins and become part of the problem. They show a strong preference for open coastal marine or freshwater locations and do not accept nest boxes placed in typical upland "back yard" situations, but are just beginning to show interest in upland sites as coastal colonies become saturated.

As of 2018, most occupied Western Purple Martin colonies in BC were still located on pilings along the marine coastal foreshore in bays, estuaries, and marinas, in or beyond the intertidal zone within the Georgia Basin. They are also at least 50-100m away from trees and other tall structures on the foreshore that might provide hunting perches and approach cover for ambush predators, mainly small hawks and falcons.

Apart from several early site colonizations along the lower Fraser River, east of Vancouver (after a 40+ year absence!) in 2006-07, of which a small colony near Harrison Mills remains active, and more recent occupations since 2013 at an increasing number of lakes and wetlands near the coast (e.g. Buttertubs Marsh, Westwood and First Lakes in Nanaimo, Crofton Lake near Crofton, Comox Lake near Courtenay, Burnaby Lake in Vancouver. etc.), there are no nest box sites in use inland of the marine coast in the Georgia Basin. Purple Martins in BC historically used fresh water sites for nesting here and results of monitoring since the 2013 nesting season indicate we are beginning to have some success re-introducing them to similar suitable nest sites without House Sparrow populations or large numbers of Starlings. For this reason we encourage placement of nest box clusters on snags, pilings, and other offshore structures at fresh water sites on lakes and marshes. It may take a few more years for them to adapt to this situation, but if they do take a liking to your fresh water colony site please let us know.

It's also important to note that, unlike other native cavity-nesting members of the swallow family that nest in both the wild and in human-supplied nest boxes, Western Purple Martins in BC are currently completely dependant on human-provided nest boxes and would not be nesting in the province at all without them. (The nearest known original snag-nesting site is at Fort Lewis in southern Puget Sound, Washington.) One long term objective and major challenge of the Stewardship and Recovery Program in BC is to re-introduce martins to nest sites in their original habitat (or a reasonable modern equivalent) where they may become self-sustaining, rather than develop a population of semi-domesticated birds entirely dependant on ongoing human provision and maintenance of nest sites. Recovery results so far suggest this goal is very likely achievable in time, given a continued strong stewardship effort, continued population growth and the existence of sufficient natural cavities in snags in suitable habitat in the wild. Recent documentation of Western Purple Martins nesting successfully in woodpecker cavities in mechanical harvester-topped and killed "created snags" in central Oregon (M. Hane, unpub. data) provides additional promise in this regard.
 

B.C. Purple Martin Recovery Program Sponsor Spotlights

Gold ($20,000 & over)

2007 - VanCity enviroFund

Silver ($10,000 – 19,999)

2006 - Environment Canada EcoAction                      2005 - VanCity enviroFund

Bronze ($5,000 – 9,999)

2013 - HSRDC Canada Summer Jobs                        2013 - Western Purple Martin Foundation
2012 - Western Purple Martin Foundation                  2011 - HRSDC Canada Summer Jobs                       
2009 - HRSDC Canada Summer Jobs                        2008 - HRSDC Canada Summer Jobs                       
2008 - BC Transmission Corporation                          2007 - HRSDC Canada Summer Jobs                       
2006 - HRSDC Summer Career Placement              2005 - Environment Canada EcoAction                      
2005 - HRSDC Summer Career Placement

For more information, see our Recent Publications below, visit our Purple Martin Links, or find out about our Adopt-a-Purple-Martin Program

Recent Publications

NEW 2013! - Status Report on the Western Purple Martin in BC, with previously unpublished results of biological research and population monitoring

Cousens, N. B. F., and J. C. Lee. 2012. Status Report on the Western Purple Martin (Progne subis arboricola) in British Columbia. Prepared for the British Columbia Ministry of Environment, Victoria, BC. 117 pp. (Electronic resource).

Western Purple Martin genetic relationships - comparison of eastern and western populations using mitochondrial DNA analysis

Baker, A. J., A. D. Greenslade, L. M. Darling and J. C. Finlay. 2008. High genetic diversity in the Blue-listed British Columbia population of the Purple Martin maintained by multiple sources of immigrants. Conservation Genetics, Vol. 9, Num. 3, June 2008.

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