Special to The Record | USA TODAY NETWORK - NEW JERSEY 

   Back in 2010, when I worked in the Meadowlands, New York City Audubon researcher Liz Craig got word that a snowy egret that she’d previously banded had been seen in a Carlstadt marsh.   

  Craig did not locate the small wading bird, but when she held up a large antenna, she picked up the radio signal from a great egret that she had equipped with a miniature transmitter three months earlier on an island in the East River.  I was impressed that technology could be used to document the peregrinations of an egret on a 10-mile foraging trek across the skies of Manhattan to New Jersey.

  That was then. This is now. That early hand-held technology has been supplanted by a global network of radio towers.  

    Researchers affiliated with a non-profit group called Motus (the Latin word for “movement”)  use automated radio telemetry to track all sorts of birds, bats and insects over vast distances thanks to tiny transmitters called NanoTags. The network of radio towers in 34 countries can record the signal from any NanoTag that passes within 15 kilometers of it – and then share the data.

   The Meadowlands Research and Restoration Institute has one of the 1,814 Motus radio towers, and researchers there have been using the NanoTags to track migration patterns of catbirds and song sparrows for the past two years. 

    “NanoTags are as small as a pumpkin seed – the edible inside part without the shell – plus a thin antenna,”  says Cailyn O’Connor of Kean University, who works with MRRI. 

    The tags' small size makes it easy to deploy. “There are many ways to attach a NanoTag but we use a ‘leg loop’ harness, which a bird wears as a sort of backpack, but on a leg,” she says, 

   So far, MRRI has tagged more than 100 birds, and MRRI’s Motus data has produced some fascinating results..

    “We’ve learned a lot about the migratory routes of Meadowlands birds,” says O’Connor. “For example, we've recorded many catbirds in Florida on their way to the Caribbean. The catbirds over-winter there, and we've picked up many spring migrations back up once they hit the United States again.”

   According to MMRI senior biologist Drew McQuade, the tower has also detected hermit thrushes, kestrels, and other birds tagged at other stations, which shows that the birds are coming through the Meadowlands on migration.

    MMRI also uses the Motus information to support its efforts to restore and conserve habitats.  “It shows that the restored sites and capped landfills of the Meadowlands are important refueling sites for these migrant birds,” he says.  

     What’s next? “We’re looking to expand our study species to include some warblers, thrushes, and Savannah Sparrows, which are a threatened species in New Jersey,”  McQuade says. 

     The Bird Watcher column appears every other Thursday. Jim’s latest book, "The Screech Owl Companion,"  was published last month by Timber Press. Email Jim at [email protected].