Western Purple Martin Foundation
Martin Banding Study
Master Bander, Cam Finlay, and his volunteer assistants started Purple Martin banding studies in BC in 1996. The initial 5-year study investigated dispersal and genetic mixing within the BC Purple Martin population. This study showed that the population was well mixed and an expansion of the nest box program would benefit their recovery.
We have been able to continue an annual nestling banding program thanks to the on-going generous support and/or financial contributions of the following sponsors: James L. Baillie Memorial Fund of Bird Studies Canada with funds raised through the annual Baillie BIRDATHON, BC Hydro, Canadian Wildlife Federation, Canadian Wildlife Service, Georgia Basin Ecological Assessment and Restoration Society, HRSDC Canada Summer Jobs, Island Timberlands and TimberWest.
The annual nestling banding program has been continued to collect information on dispersal between colonies, age composition, and survival by age and gender, as well as the declines and increases in population numbers primarily as a result of changing weather conditions. Nest inspections before eggs hatch also provide important information on productivity, which varies with weather conditions and available food supply, as part of our overall scientific monitoring program.
Each year we band nestlings that are 10-days old and older at most BC colonies with a coloured, numbered band on one leg and a US Fish and Wildlife numbered aluminium band on the other. The coloured bands alternate on a four-year cycle of gold-left, gold-right, blue-left and blue-right. Each coloured band has a unique 3-digit number and letter code plus ‘BC’.
The banding of nestlings is the easy part. The leg band reading takes many hours of dedicated time. Each spring when the martins return from South America we use a spotting scope to read the coloured numbered leg bands on as many birds as possible at ~20 of the most accessible colony sites. We read about 300 leg bands each year on previously banded birds, which provides a representative random sample of ~20-30% of the BC population.
Recent band reading data shows that the BC Purple Martin population continues to be well mixed. For example, birds banded at the Ladysmith Maritime Society marina colony, the largest colony on Vancouver Island, are observed at martin colonies from Victoria to Campbell River, on the Sunshine Coast, the Lower Mainland and in Northern Puget Sound. Similarly, each year the Ladysmith colony contains martins from most other BC colonies and some in Puget Sound. Martins banded at colonies in Northern Puget Sound through an associated Washington nestling banding program have also been seen at BC colonies as far north as Campbell River.
Preliminary analysis of band reading data showed that subadult birds colonised new sites when established colonies became full between 2003 and 2006 when the BC population was expanding. We also found that low nestling survival due to food shortages during cold wet weather resulted in a lower subadult recruitment in the following year leading to population declines, as seen in 2007, 2008 and 2009.
Longevity records have also been recorded for BC Purple Martins as a result of the long term banding study. In 2007 we observed a 10-year old adult male banded in 1997 and a 9-year old female banded in 1998, both longevity records at the time for western martins. In 2008, this female nested successfully as a 10-year old and continued to hold the longevity record for female western martins. This longevity record was broken in 2009 when two 11-year old females were observed. One was the female seen in 2007 and 2008. The other 11-year female had not been seen before at any colony where band reading regularly occurs. Where she has been all these years is anyone’s guess. Paired with younger adult males neither bird nested successfully in 2009, and it is uncertain whether they survived the season and will return in 2010.
In 2008, two BC banded birds were found in the Willamette River valley, SW of Portland, Oregon during spring migration, for the first time giving us a glimpse into a part of their return trip from South America.
The BC Purple Martin population continues to move through the cycle of growth, decline and recovery with an overall increasing population trend. Therefore, we will continue the long term banding study for a few more years to collect additional information on the affects that weather has on survival and age composition.
Website funded in part by the Ladysmith Maritime Society
Original website design by Danielle Morrison
Last modified 18 Aug 2009