About Geolocators

About Geolocators

Geolocator Model MK-12
About Geolocators
A geolocator being hooked up to a computer for data download
Until recently, scientists knew little about songbird migration.  They speculated and hypothesized based on the rare recoveries of banded birds on the wintering grounds. Although these discoveries were exciting, they did little to reveal the mysteries or details of the actual migration. 

In 2007, however, a giant leap toward understanding songbird migration occurred when Dr. Bridget Stutchbury of York University, in a ground breaking study (published in
Science, February 2009), tracked the first songbird migration using tiny geolocators harnessed on the backs of purple martins, Progne subis

Geolocators work by measuring light levels. Very simply, special software uses these light measurements to calculate the latitude and longitude allowing analysis of where the bird was when.  Geolocators have some limitations.  Because of their tiny size, tiny battery, and tiny battery life, birds have to be re-tagged annually.  Additionally, geolocators do not use GPS (yet!) and must be removed from the returning bird to retrieve the data.


The biology of purple martins makes them ideal candidates for this type of study.  (Please read more about them and about the plight of our aerial insectivores in the
About Purple Martins page.)  They are neo-tropical migrants (wintering in South America) with a relatively long distance migration.  Because they are dependent on man-provided housing and have strong site loyalty, they can be relatively easily recaptured.  Although on average, one can only expect a 50%-60% migration survival rate, approximately 92% of the surviving birds return to the colony from which they started, making the retrieval of geolocators possible.

In our last publication (See the 'Publications" page), we showed that the declining numbers of our northern aerial insectivores vs. our stable southern populations (using purple martins as a model species) is not due to different environmental factors on the wintering grounds as previously hypothesized.  Using geolocators, we were able to show that both the northern and southern populations of martins winter in the same geographical areas.  This study is a world-first, using the largest sample size yet for tracking songbirds and shows why geolocators are so important for unraveling the causes of breeding declines in migratory birds.


Since this discovery, our research has taken a new and even more exciting approach to help us figure out why our northern populations of insectivorous birds are experiencing such steep population declines.

In 2013, we will be combining our geolocator research with a genetic component.  It is known that all creatures possess a 'clock' gene that, in migrating birds, tells an individual when to begin migration.  The amount of variation in this gene within a population should translate into the spread of departure dates from Brazil that we can measure with geolocators.   Northern populations are expected to have little variation in migration timing, because it is so costly to arrive too early (when it can still snow!)  Insectivorous birds can starve to death in as little as three days without food (flying insects) which can occur in temperatures below 50°F.

We will be conducting genetic research by taking blood samples (for DNA) from purple martins (our model species) across their summer breeding grounds from colonies stretching from Texas to Alberta.  In addition, we need to be able to match individual timing to identify early vs. late birds, using geolocators, and then match this to the individual's genes.  Why is this important for conservation?  Genetic control of migration timing, if strong, means that populations and individuals from northern populations cannot adapt rapidly to climate change.

If migration timing in purple martins is strongly controlled by genetics, the result could be the loss of these (and possibly all) long-distance, migratory, insectivorous birds in the northeastern region of our continent.  This research may be the catalyst to implement immediate and critical conservation efforts.

Below is a PowerPoint presentation that describes the 2011 and 2012 geolocator project. It includes some of the actual migration maps.

If you are concerned about the plight of our northeastern insectivorous birds, please either purchase my jewelry (All profits go towards research expenses.) or a 'Direct Contribution' (All proceeds go towards geolocator acquisition.) from my 'Store' page.  These funds are absolutely necessary to conduct further research from my colony.

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