Mayne Island participates in the BC Purple Martin Stewardship and Recovery Program, coordinated by the Georgia Basin Ecological Assessment & Restoration Society (GBEARS) out of Nanaimo. Western purple martins are a threatened species on the west coast of Canada and an at-risk Species of Special Concern throughout its breeding range in the western USA, and this project is dedicated to the restoration of the BC population.
Purple martins are the largest members of the swallow family. The males' feathers are a deep, lustrous purple and black. The females are grey with shiny purple highlights on their heads, shoulders and backs. The sub-adult birds of both sexes look more or less like adult females during their first year. The birds winter in South America and migrate to the west coast of North America to breed between mid April and August.
Western purple martins are colonial nesters but prefer single nest boxes clustered together in colonies (rather than the apartment-style bird houses preferred by their eastern cousins). As well, western purple martins currently nest only in boxes mounted on pilings over the water. They used to be more abundant on the west coast, but their numbers declined drastically in the middle of the 20th C. due to competition for nest cavities on land from starlings and house sparrows (which nest earlier), habitat loss (dead tree removal) and changes in building design (fewer nooks & crannies).
Mayne Island began participating in this stewardship and recovery project in 2005 with nest boxes in two locations, and we hosted our first purple martins in 2006. Ten boxes are mounted on isolated pilings next to the Mayne Island Resort's dock in Bennett Bay, and 10 are mounted on the public dock in Miners Bay. Occupancy rates are currently close to 100%, and chick production has tended to increase over the years: 2006 (35); 2007 (42); 2008 (35); 2009 (34); 2010 (56); 2011 (60+); 2012 (60+). The birds are aerial insectivores and are vulnerable to cool, damp weather events that ground their insect supply. This is crucial early in their breeding season when they need adequate food to recover from the rigours of migration and come into breeding condition. It is also critical when their chicks are young. For example, in 2008, 49 chicks were banded, but shortly after banding the weather turned cold and wet and only 35 chicks survived. That weather event reduced chick survival in purple martin colonies throughout the southern Georgia Basin. As a result, fewer birds returned to nest in 2009, hence the low chick number in that year, too.
Stewardship of the colonies involves opening the boxes when the first "scouts" arrive, reading the birds' leg bands to ascertain their provenance, monitoring the birds' activities to estimate the optimal time for chick banding, and cleaning and closing the nest boxes when the birds have migrated south. [The boxes must be kept closed until the martins return or they will be taken over by starlings and house sparrows.]
Our boxes join more than 1100 others on southeastern Vancouver Island, the Gulf & Discovery islands and the lower mainland, the northern-most edge of the western purple martins' breeding range. Mayne Island's participation in this project has been enhanced greatly by the efforts of many volunteers, financial support from Local Islands Trustees, and invaluable support from Parks Canada when a boat is required to access nest boxes for chick banding and maintenance.
From early 2013 Mayne Island Conservancy volunteers have been assisting the Rochet's with these recurring maintenace tasks. For more information about the BC Purple Martin Stewardship and Recovery Project, visit the GBEARS website and click on "projects." For specific information about the project on Mayne, email Herbie Rochet or phone 250-539-2831)
The Conservancy has also made contributions to the project from IBA funds and we receive dedicated donations from our members and others. We thank Cedar Townsend Christie for her most recent donation.
|Female western purple martin bringing food to her chicks in Miners Bay. (photo credit: Bernard Rochet)||Nest box cluster in Bennett Bay (photo credit: Bernard Rochet)|
|Western purple martin chick 9-10 days old and about to be banded (photo credit: Bernard Rochet)||Male (left) and female purple martins on the porch of their nest box (photo credit: Malcolm Jolly)|
Western Bluebird Restoration
Once a common species within Garry Oak ecosystems on Vancouver Island and the southern Gulf Islands, Western Bluebirds (Sialia mexicana) thrived until the 1950s, when their numbers began to decline. Since 1995, they have not been known to nest successfully in this region, and are considered extirpated (locally extinct). Some possible reasons for their absence include the reduction of insect prey due to pesticide use, loss of Garry Oak habitat, removal of standing dead trees, and competition for nest holes with exotic bird species such as European Starlings and English House Sparrows. Western Bluebirds are secondary cavity nesters, meaning that they cannot build their own nest cavities, and depend on old woodpecker cavities, natural holes in trees, or nestboxes.
The five-year Bring Back the Bluebirds Project, led by the Garry Oak Ecosystems Recovery Team, Ecostudies Institute, and the Province of BC, began this spring of 2012 with the translocation of four breeding pairs of Western Bluebirds (two with nestlings) from a healthy population in Washington State. The project aims to re-establish a self-sustaining breeding population on southeastern Vancouver Island and the southern Gulf Islands (the "Salish Sea" area).
September 2014 Update
Last week marked the official end of the 2014 field season for the Bring Back the Bluebirds Project. With 4 families leaving their nesting territories several days earlier than expected, and a 5th showing a decreasing interest in their supplemental feeder, we leave the Cowichan Valley confident that the 5 breeding pairs and their many juveniles are finding an abundance of naturally-occurring prey to build up their energy reserves for their fall migration.
Looking back on the breeding season, this has been an impressive year: we saw both a greater number of bluebirds returned and a higher success rate with translocations than in 2012 or 2013. The season began with the return of 8 bluebirds, including 2 breeding pairs and 4 of their offspring (all males) that had hatched in the Valley last year. Between March and May, 6 breeding pairs were translocated from southern Washington and released after acclimatizing briefly in aviaries. While 2 pairs headed immediately south again after being released, 7 translocated pairs decided to remain in the Valley and select a breeding territory from amongst our many nestbox host properties. In June, 3 more breeding pairs, along with their first broods, were translocated and released. These families also remained in the valley as the breeding pairs went on to establish a territory for their second nests of the season.
With more breeding pairs than in the past, it makes sense that we also saw more successful nests, more failed nests, higher mortality and, most importantly, more bluebirds hatched this season. With so many breeding territories came a host of novel situations to be adapted to and challenges to be overcome. Predators claimed the lives of nestlings, adults, a juvenile, and even entire clutches very early on in the season. We responded to the threat of depredation by adopting of a wide variety of customized predator guards and surveillance around the bluebird nestboxes. Another novel threat this year was competition with non-native English House Sparrows. While the threat of House Sparrows loomed at almost every territory, one bluebird pair had two successive nests attacked by the aggressive, territorial birds. The various competitor management strategies we applied were not enough to prevent the attacks, which claimed the lives of several nestlings and required the lengthy rehabilitation of four others.
Fortunately, every nest with a predator exclusion device located a safe distance from a large House Sparrow population fledged nestlings. Consequently, we are pleased to announce that 8 successful bluebird nests produced as many as 50 juveniles this season. The incorporation of the aforementioned strategies to safeguard each nest, the involvement of Salt Spring Islandís Island Wildlife Natural Care Centre, participation of several invaluable volunteers and, of course, the perseverance and determination of the bluebirds, all contributed to the Projectís success this breeding season.
Looking ahead to 2015, it is hard to predict what might happen. The two bluebird pairs that returned to the Valley are no more, after both females were eaten on their nest by a predator; will the males return next season with new mates? Will any of the translocated pairs that bred here successfully return next year? This year all of the unpaired bluebirds that returned to the Valley for their first breeding season were males; next year the sex ratio may not be as skewed, allowing for the formation of new breeding pairs. Finally, it is thought that only a very small percentage of bluebirds will return to where they were hatched the previous year; however, if 4 bluebirds--of approximately 40 that hatched in 2013--returned this year, even more may return next year. For the answers to these questions and many others, we will have to wait until next spring. In the meantime, Cowichan Valley residents can continue to enjoy the sights and sounds of bluebirds into September. By October, those of us that live further south should be on the lookout for these bluebirds as they begin to migrate.
To learn more about the Bring Back the Bluebirds Project and other oak ecosystem conservation projects, check out our most recent enews:
http://newsletters.rocketday.com. To support the project, visit www.goert.ca or become a GOERT member.
The public can report possible bluebird sightings to firstname.lastname@example.org or 250-383-3427. To learn more about and support the Bring Back the Bluebirds Project, see www.goert.ca.
|Banding a baby bluebird (photo credit: Bill Pennell)||Western Blue bird nestling newly banded (photo credit: Bill Pennell)|
|Western bluebird fledgling (photo credit: Bill Pennell)||Western bluebird adult (photo credit: Bill Pennell)|