Club Project: Western Purple Martin Nest Boxes

Staffan Lindgren

Purple Martins, Progne subis, are the largest swallows in North America. The Western Purple Martin subspecies, Progne subis arboricola, is distinct from its eastern cousin in several respects. It originally nested in available cavities made by Northern Flicker and other primary cavity nesters in snags. Due to on-going clear-cut forestry practices and agricultural and urban development, such snags became increasingly rare, leading to near extinction of the species in BC. By the early 1980’s, fewer than 10 nesting pairs were documented along the eastern coast of Vancouver Island.

Figure 1. Female Western Purple Martin at her nest box on Newcastle Island. Photo: Staffan Lindgren.

When a few Purple Martins were observed nesting successfully in cavities in old untreated offshore pilings in Esquimalt Harbour and at Cowichan Bay 1985, the BC Provincial Government had a small number of individual nest boxes added to the pilings to see if Purple Martins would use the boxes. The following year several of the boxes were used by Purple Martins. The BC Provincial Government then let a contract to have 200 nest boxes built. These nest boxes were distributed to naturalist groups to install at marinas and offshore pilings sites from Victoria to Campbell River. The following year Purple Martins were seen nesting in some of the new nest boxes.

Over the years the population has slowly increased and additional nest boxes were added to each site, under the direction of the Georgia Basin Ecological Assessment and Restoration Society (GBEARS), in Nanaimo. The current population is now estimated at ~1,200 pairs. However, the Western Purple Martin is still considered vulnerable as they are sensitive to inclement summer weather, starving after only 3-4 days if unable to catch large aerial prey (e.g., dragonflies and moths) that they feed on and feed to their growing young. 

Nest boxes originally set up many years ago are now seriously deteriorating, and require replacement. Of 1700 boxes currently distributed among 100 sites, ~ 500 require replacement within the next few years (B. Cousens, pers. com.) Therefore, Nature Nanaimo is engaging club members to build some replacement nest boxes.

Figure 2. A mounted Purple Martin nest box. This model is slightly different from the boxes we built.

In the fall of 2018, Nature Nanaimo decided to apply for funding to build nest boxes for Purple Martin in support of the conservation efforts led by the Georgia Basin Ecological Assessment and Restoration Society (GBEARS). A proposal was written by Staffan Lindgren, aided by Nature Nanaimo members Bruce Cousens and Charlene Lee who are spearheading the conservation efforts by GBEARS. The proposal was submitted to BC Nature and the BC Naturalists Foundation, and we were notified in February that we had been successful.

At subsequent meetings a sign-up list was provided to recruit Nature Nanaimo volunteers, and we had a very good response, with a total of 24 members signing up. Josef-Mathias Baur offered the use of his well-equipped workshop for the work, and he quickly took charge of acquiring lumber and miscellaneous equipment needed. Staffan Lindgren purchased additional materials needed, as well as 2 electric staple guns to prevent injury due to the number of staples needed for the aluminum roofing.

Figure 3. Nature Nanaimo volunteers cutting the lumber for Purple Martin nest boxes. Photo: Staffan Lindgren.

The work started on March 19 with five volunteers. Over the following weeks, boards were cut, and about 60 boxes were assembled by 11 of the volunteers. The final boxes were assembled on April 9.

When informed of the completion of the nest box building, Bruce Cousens requested that we make predator guards, which consist of 2×2 inch stucco metal mesh, which is mounted on top of the boxes. Helena Kreowska offered her carport for this part, and three of us completed 60 guards on April 16.

Figure 4. Staffan Lindgren, Helena Kreowska, and Josef-Mathias Baur with some completed traps, one of which has Josef’s custom-designed roof.

In total, volunteers contributed 100 hours of labour to this project. Nest boxes are being handed to GBEARS for mounting in batches of 10. The nest boxes will replace old deteriorated boxes that are as much as 36 years old.

Figure 4. Example of the card acknowledging the funding from BC Nature and the BC Naturalists Foundation and mounted under the porch of each box. Photo: Staffan Lindgren
Figure 5. Bill Lesiuk making Predator guards. Photo: Staffan Lindgren

In summary, this was a very successful project. A big thank you is due to all Nature Nanaimo members who volunteered. The Purple Martins also thank you.