Western Great Lakes Bird and Bat Observatory

The Observatory's Motus Tower

Motus Map

Motus Tower


The Observatory has taken the lead in extending the Motus Wildlife Tracking Network to southern and eastern Wisconsin. The goal: to build a network of radio towers east to west across southern Wisconsin and north to south along the Lake Michigan shoreline, from the Green Bay area southward. To make this happen, the Observatory has hosted regional meetings, attended workshops, raised funds, and worked with a variety of partner organizations and individuals.

Observatory Director Bill Mueller, who has been coordinating these efforts, reports that as of late August, three stations already were on line, with more soon to come. (See the map above and a special message about Motus from Director Mueller below.) The Motus towers in southern and eastern Wisconsin will be vital for tracking bird migration across Lake Michigan and the state of Wisconsin.

From southwest to north, the newest Motus towers are located at Camp Whitcomb Mason in northwestern Waukesha County, at the Observatory’s headquarters at Forest Beach Migratory Preserve in Ozaukee County, and at Woodland Dunes Nature Center in Manitowoc County.

Next to come are stations at Madison Audubon Society’s Goose Pond Sanctuary in Columbia County, the Milwaukee County Zoo in Milwaukee County, and Eagle Valley Nature Preserve in Grant County, and a yet-to-be-determined location in Iowa or Sauk County, near the lower Wisconsin River.

The term Motus comes from the Latin word for “movement.” The new technology is a huge contrast to earlier methods for tracking animals. In the Motus system, birds carry tiny radio transmitters whose signals are picked up by receivers (usually mounted on towers), and the information is collected by scientists.

Marking birds to trace their movements is a centuries-old practice; in America, John James Audubon tied silver thread around the legs of Eastern Phoebes in 1805 to see if they returned to his farm in successive years. The use of metal bands to track migratory patterns got its start in Europe in the late 1890s, and the first American study to use banding was designed by Smithsonian researchers in 1902. Banding became more standardized in America in the early 1900s and was revolutionized in the 1950s, when nearly invisible mist nets -- used to capture birds safely -- became more available. Banders now undergo a rigorous federal certification process.

Bands are read or recovered when birds are recaptured or when they are found dead. Although these bands provide good information, a lot of effort goes into a system that brings less than a 10% recovery of songbird bands and a 30% to 40% return on game birds like waterfowl.

Radio telemetry has been around since the 1960s but has been hampered by transmitters that were too heavy to be used on small animals and by the fact that they often required scientists to wander the landscape with bulky, hand-held antennae. More recent telemetry methods use GPS transmitters and satellites.

Motus transmitters (nanotags) can be attached when birds are banded, and the transmitters are so small that songbirds, bats, and even large dragonflies and butterflies can be studied. Once birds are carrying a transmitter, they generate information without being recaptured, simply by flying within 9 to 12 miles of a receiver. Researchers can track multiple birds simultaneously. Transmitters can be set to send out pulses in a coded sequence specific to each project. Small batteries or those that signal frequently may last only a few weeks, but larger ones may transmit for as long as three years.

Motus allows migration to be viewed as more than just a movement between Point A and Point B. It shows how birds respond to physical barriers like water or mountains. (Do they go around or across? In one big push, or in increments?), how long they rest and refuel at stopover sites like Forest Beach, how weather influences movement, whether the age or sex of a bird affects the way it migrates, the times of day that birds are active, their flight speeds, flight orientation, and much more. The Motus system encourages scientists to ask “bigger” questions than the old systems allowed.

The key to making Motus work is a network of receivers that are strategically located in order to form an electronic “fence” that can track birds from point to point for thousands of miles. Today, there are more than 720 receiving units on four continents -- more than half of them in the US and Canada. 
Private individuals or landowners can help by funding and/or giving permission for a station on their property, if the location is right. Part of the Observatory’s role as coordinator includes rounding up funding. The cost for erecting a tower is between $5,000 and $7,000, occasionally more in remote areas; if you’d like to fund a tower (or part of one); please contact the Observatory.

For more information:
https://www.birdlife.org/americas/news/tiny-transmitters-tracking-birds-north-south-america (shows a bird with a transmitter attached)