Satellite Tracking Update

December 28, 2018

 

There's exciting news from the North as we continue to track the movements of three young snowy owls, from their nest site through their first year of life.

 

Earlier this fall, we had seen that two of the three chicks had started moving away from their birth (or natal) grounds at Utquigvik, formerly Barrow, Alaska. We'd been concerned that the third chick's signal stayed in Utquigvik, suggesting it might have died. Now, though, we just received news that the third chick might also be on the move.

 

To track these owls moving across regions where the cell phone network is mostly nonexistent, we've had to rely on Argos satellite technology instead of the GSM cell phone network as we do with our standard transmitters. The units we are using on the chicks are much smaller than the ones commonly used by Project SNOWstorm over the years; they carry no solar panel, with power coming only from a small internal battery. Given their overall lower size, the transmitters record their location much less frequently than we do with GSM.

 

We went a long way to save each micro-volt of battery power so the units could track the birds for a longer period -- up to two years. So we programmed the units to record their location only once every five days, which is relatively infrequently but still sufficient to assess dispersal and survival rates, our two main questions. Only when the unit has collected at least three locations does it transmit that data to us via the Argos satellites. The rest of the time, the unit goes into sleep mode to save power. This means that in the best case scenario, we would receive an update every 15 days -- but that doesn’t take into account all the other issues that could prevent the transmitter from connecting with the satellites at a given time. For instance, the bird could be in a valley or close to a building that blocks the signal, or the orbiting satellites could be too low on the horizon at the time the transmitter turns on and tries to send data.

 

Despite those challenges, we chose this technology to answer very specific questions -- primarily dispersal movements and juvenile survival rates -- that wouldn't be possible using GSM technology because as you move north of the boreal forest, the cell phone network is scanty at best. For each recorded location, the Argos system also provides a value of accuracy, which depends on the number of signals received and the time between them. In other words, it's a check on how reliable the location is.

 

So in the latest update, the locations we received for Blanche, in the westernmost section of the Alaskan North Slope somewhere near Cape Beaufort, are of low accuracy, which mean the bird is "most likely" there – we need to keep in mind that there is a chance this is only a glitch, and we'll have to wait and see what location comes next! So this exciting result still needs to be taken with some caution at this point. The other two birds (Ookpik and Tundra) have both made movements away from their natal grounds and in each case, the accuracy of the locations were high, so we are very confident these movements weren’t outliers. Tundra is now near Wainwright and Ookpik is in the National Petroleum Reserve - Alaska, a 23.5 million-acre tract that represents the largest area of undisturbed land in the U.S.

 

We knew that tracking snowy owl chicks would come with some limitations, and at times a bit of frustration in our current world of “I want it here and now”. But reliable estimates of dispersal and survival will only come through careful scientific design and, in this case, patience! This is nonetheless very exciting.

 

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Text courtesy of JF Therrien, Ph.D., Senior Research Biologist, Hawk Mountain Sanctuary

Snowy Owl photo courtesy of © Kurt Lindsay

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