BC Purple Martin Stewardship and Recovery Program

Purple Martins are the largest swallow in North America. The western subspecies (Progne subis arboricola) is threatened in British Columbia. Historically, 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. Due to logging, fire prevention, snag removal, burned timber salvage and agricultural and urban development throughout their original breeding range around the Georgia Basin, this habitat has been destroyed. Increasing populations of non-native European Starlings and House Sparrows also provide strong competition for any remaining nest cavities. By the early 1980s the BC population of western Purple Martins was reduced to less than 10 breeding pairs.

Since then, the British Columbia population of Purple Martins has rebounded to over 200 pairs by 2002 and ~650 pairs by 2007. This is largely 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 in Puget Sound, Washington, in 1975.

The BC population increased dramatically between 2003 and 2006, due in part to good weather conditions throughout the breeding season, resulting in an ample food supply of flying insects for both adults and nestlings. As for other swallows, the nesting success of Purple Martins is highly sensitive to adverse weather-induced reduction in food supply availability. 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.

d 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 Oregon and possibly 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. These are believed to be western longevity records for males and females in the wild. Most martins that survive their first winter live only 2-3 years and very few exceed 5 years of age.

In addition, the long term banding study is now providing 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.

In 2005 and 2006 a survey of remaining historic and potential new freshwater nesting sites was conducted in preparation for re-introducing 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 very scarce, particularly on south Vancouver Is. and in the Lower Mainland. Many former nesting sites in the wild have been lost to various forms of development, the snags have fallen or been removed 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.

There are currently active colonies established at the locations shown in the following map (2010):

* 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 Dewdney (2006) and Mission (2007) also not shown.

Nest Box Construction and Mounting Plans

If you would like to build your own 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 give you any help or further information you might need.

When choosing suitable nest box locations for attracting Purple Martins, it's important to keep in mind that western Purple Martins like to nest in clusters of single boxes 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 martins and tend to be taken over by non-native European Starlings and House Sparrows, which then become part of the problem. They show a strong preference for coastal locations and do not accept nest boxes placed in typical upland "back yard" situations.

As of 2007, almost all occupied Purple Martin colonies in BC are located on pilings along the marine coastal foreshore in bays, estuaries, and marinas, within or beyond the intertidal zone. 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.

Apart from 1-2 recent site colonizations along the lower Fraser River, east of Vancouver (after a 40+ year absence!), there are still no nest box sites in use inland of the marine coast or over freshwater in the Georgia Basin. Purple Martins historically used fresh water sites for nesting here and we hope to re-introduce 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 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, 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 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.
 

Purple Martin Recovery Sponsor Spotlights

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

Western Purple Martin genetic relationships - comparison of 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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Last modified: 02/02/09