Follow the light

Neotropical migratory songbirds breed in North America and overwinter in Mexico, Caribbean Islands, and/or South America. Although the wintering range of many species has been well documented, it remains unclear whether individuals breeding in western Canada occupy the same wintering range than those from Eastern Canada. Understanding migratory connectivity of songbirds (i.e. extent at which different breeding populations are occupying the same wintering area; mixing) is critical to elaborate sound conservation plans. Indeed, researchers acknowledge the importance of understanding the ecology of these migratory species throughout their annual cycle.

Archival light-level geolocators are being used by members of our lab to track the migration of the Ovenbird which is a small (ca. 20 g) songbird breeding in relatively high densities in Canadian deciduous forests. It overwinters in Mexico and Caribbean Islands, but it is unclear whether breeding populations across Canada are mixing on the wintering ground. The current technology does not provide small enough GPS units that would allow us to track Ovenbirds migration from the comfort of our office. Hence, we have to rely on tiny light sensors (0.5 g) to provide the required information.

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In 2012 and 2013, we installed geolocators on male Ovenbirds that record light intensity every minute providing values between 0 (minimum; night) and 64 (maximum; day). The data (i.e. light value, date, and time) is then saved onto the memory included with the device. These sensors have been attached to individuals at three locations in Alberta (Fort McMurray, Slave Lake, and Cypress Hills) and in New Brunswick. Each individual fitted with a geolocator also received color bands to allow us to relocate them the following year. At the end of the breeding season (August), males fitted with their new ornaments started migrating south to their wintering ground.

Teams from the Bayne’s lab are currently in the different regions trying to recapture as many returning individuals as possible and retrieve geolocators. Expected return rate is similar to those reported from band recovery studies which show relatively high fidelity to their breeding territory (i.e. return rates of 40-60%). Once recaptured, light values saved on the geolocator’s memory are downloaded into our computer and processed through a series of programs, each with a specific task. For example, Bird Tracker uses time of sunrise and sunset for a given day to calculate the location (latitude and longitude) of each bird. We then use the coordinates to map the wintering area of each individual for which we retrieved the geolocator in ArcMap). Preliminary results from individuals recaptured in 2013 and this summer suggest that there would be little overlap in the wintering areas of western and eastern Ovenbird populations. Our team is working hard to increase our sample size to allow us to make stronger inferences. We already recaptured a couple of Ovenbirds this summer and will provide more details on this exciting project at the end of the summer!

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Locations of two male Ovenbirds during summer 2012, winter 2012/2013, and summer 2013. The first individual was captured in Slave Lake, Alberta (A), whereas the second was captured in St-Léonard, New Brunswick.

Principal investigators: Erin Bayne and Samuel Haché

Assistance: Easwar Vasi and Hedwig Lankau

Collaborators: Marc-André Villard (Université de Moncton), Owl Moon Environmental (Kenneth Foster and Chris Godwin-Sheppard, and the Lesser Slave Lake Bird Observatory.

Funding agencies: University of Alberta, Alberta Parks and Alberta Conservation Association

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