Avian Radar Project
Making Wind Power Wildlife Friendly

Avian Radar Project Home

Why Migration Is Important

Wind Power and Migrants

Avian Radar Units

Acoustic Monitors

Research Results

Current Research

Interactive Radar Location Map

Evaluating Radar Studies

Radar Team

Links

USFWS National
Wind Energy Site

Midwest Wind Energy Home

 

Funding provided by GLRI Logo

Documenting Migration

Research Results

Daily Patterns

Bird and bat activity differs greatly between day and night. During the day, bats are not active and birds are performing shorter, lower altitude flights looking for food and are not usually traveling in one specific direction. Many of the birds that are migrating are foraging within the woods and fields to replenish their energy or are resting before traveling the next night. Some birds such as hawks, cranes, vultures, and waterfowl do migrate during the day though. As dusk approaches, many birds start moving towards the tops of trees, readying to take off for migration. Once it is dark enough for them to travel without risk from predators, they take off and start their migration. Activity on the radar picks up quickly at dusk and increases until around midnight. Numbers then start to decrease as dawn approaches and some migrants start to land. At dawn, numbers drop off dramatically once it is light out as the migrants seek out shelter. The low daytime activity then begins the next day. A graph of typical daily activity is shown below for multiple sites. Data was averaged over the fall 2011 and 2012 seasons.

 

Daily Activity Pattern

 

This graph of activity can also be examined by looking at the Trackplots during a 24-hour period at one of the sites. The animation below shows a set of hourly trackplots from noon on one day until noon on the next day. Each trackplot represents an hours activity. Activity is low during the day, and increases quickly as dusk arrives and peaks in the middle of the night, slowly decreasing until dawn when activity returns back to its low daily level. The vertical and horizontal trackplot animations are synced so that the same time shows on both animations. The time is displayed on the top of the horizontal trackplot in a 24 hour cycle.

 

HSR Trackplot Animation VSR Trackplot Animation

 

Timelines

If we display hourly activity out over the entire season, instead of summing it up by averages, we can see the graph shown below. Migrant activity is pulsed, often occurring for several nights in a row before having a small lull in movement and then picking up again for the next pulse. The peak activities on both the horizontal and vertical radars all occur around midnight. As the migration season ends, peaks become smaller and occur less frequently. By looking at the entire season like this, we can start to see when the most at risk times may be. Variation does occur between years as well and we are currently looking into how activity patterns relate to weather events (barometric pressure, wind direction, precipitation, etc.). With this analysis, in the future we may be able to predict when migrants may be at greatest risk from impacts by wind farms.

 

Fall 2011 Timeline

 

The graph above only examines the hourly counts from one of our antenna. If we plot the counts from the horizontal radar along with the vertical radar counts and zoom in to further examine the graphs we can get an even more detailed picture of what is occuring on the landscape.

 

Migration timeline

 

The portion of the timeline above shows what migration numbers look like on both antennas. Peaks usually coincide between the horizontal radar antenna counts and vertical radar antenna counts and these peaks occur right around midnight. The graph below is from a low migration time period late in the fall season. A different pattern of peaks emerges later in the season when migration is dwindling, even though numbers on the horizontal antenna can remain high. These peaks occur right around dawn and dusk and are not accompanied by peaks on the vertical radar. This pattern is indicative of birds (in this case geese and gulls) moving between feeding and roosting grounds twice daily.

 

Low migration timeline

 

The differences between these graphs underline the importance of looking at the data on fine temporal scales (i.e. hourly) instead of lumping the numbers into the whole season. It also shows the importance of using data from both antenna to get a better picture of what is occuring on the landscape.

 

Migration Phenomena

 

Migration and Non-migration

During the migration season, pulses of migrants move through an area. Each night however, may not have a large number of migrants moving. This may be due to unfavorable environmental conditions or a variety of other factors. Below are trackplots summarizing 1 hour of tracks from midnight to 1 AM on a night with migration and a night soon after that did not have migration.

Migration on the HSR Migration on the VSR

Horizontal and Vertical Trackplots from Migration Night

Non-migration on the HSR Non-migration on the VSR

Horizontal and Vertical Trackplots from Non-Migration Night

Heavy and Light Migration

Even when migrants move through an area, they don't always move in the same magnitudes. Some nights have many more migrants traveling than others. We still call it migration because the targets are moving all in a concentrated direction, even though they may not be in large numbers. The differences in magnitude of targets moving each night may also be related to environmental factors such as temperature, wind speed, and wind direction. Below are 1 hour summary trackplots from a night with heavy migration and a night with much lighter migration at the same site on the eastern shore of Lake Michigan near Luddington, MI.

Heavy Migration Trackplot

Heavy Migration - - 18,680 targets

Light Migration Trackplot

Light Migration - - 1,837 targets

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reverse Migration

Migrants do not always move in the expected direction. Occasionally they will travel in the opposite direction than we normally associate with migration. This would mean moving north in the fall and south in the spring. Again, this phenomena is likely associated with environmental factors, such as an unexpected cold spell in the spring forcing targets to move south to find food. Below are example 1 hour summary trackplots from spring and fall sites on the western shore of Lake Michigan near Manitowoc, WI showing reverse migration. The color of the tracks indicates the direction the target was flying in according to the color wheel in the upper right corner. Orange and red tracks are moving in a southerly direction and blues and purples are moving in a northerly direction.

Fall Reverse Migration

Northward (blue) movement in fall

Reverse Migration Spring

Southward (red/yellow) movement in spring

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Migration Direction Variation

As with reverse migration, the direction that targets move in is not always north and south. Even at one site we can see that the major direction of travel for migrants varies. We can see targets moving at this location in the southerly direction as we would expect as well as north, southeast, and west. These are 1-hour summary trackplots from the western shore of Lake Michigan near Manitowoc, WI. Color of the tracks indicates the direction of movement according to the color wheel in the top right corner.

 

South Migration North Migration Southeast Migration West Migration

 

Movement in to Shore at Dawn

One consistent movement direction that we have observed at each of our locations is the movement of targets that are over the water in towards shore as dawn approaches. Migrants that are traveling during the night may fly out over the lake but cannot land in the water so they must return to land. Migrating passerines (songbirds) and bats tend not to fly during daylight because of the risk from predators such as hawks and falcons. To avoid this risk, they must be in cover onshore just after dawn. As a result, dawn may be one of the highest risk times for migrants since they are flying lower to land, may be exhausted from the nights migratory flight, and are concentrating along the lakeshore where many wind turbines have been proposed to be located. Below are trackplots from an hour during the night and an hour in the early morning of the same night showing the change in movement direction approaching dawn. These are 1-hour summaries of tracks and the color of the tracks indicate the direction of movement according to the color wheel in the top right corner.

 

North-South Shoreline

This phenonena occurs on shorelines that are oriented in a north/south direction such as most shores of Lake Michigan and has been observed on both sides of Lake Michigan by our radar units. Movement is south (red-orange) at night and turns to move east (green-blue-yellow) at dawn.

 

Migration South at Night Dawn migration in to shore

Night and Dawn Fall Migration on Eastern Lake Michigan.

 

East-West Shoreline

Movement in to shore at dawn also occurs along shorelines that are oriented in an east/west direction such as the south shores of Lake Erie and Lake Ontario. Movement is to the north (blue) and east (green) at night and turns south (yellow-red) along the shoreline at dawn.

 

Nocturnal Migration East Dawn Migration in to Shore

Night and Dawn Spring Migration on Southeastern Lake Erie.

 

Seasonal Reports

Each season is unique because of various factors affecting migration such as large scale weather patterns affecting when migration starts and ends, the passage of fronts that affect timing of pulses, and other factors that control the emergence of insects that are food for many bats and birds or are food for their prey. Additionally, we moved the radar units and acoustic monitors to different locations each season with different research goals. Below are links to completed reports for the radar units and the acoustic monitors.

 

Radar Units

Fall 2011 Seasonal Report is under review and will be added here shortly.

 

Acoustic Monitors

2012 Acoustic Monitor Report

2011 Acoustic Monitor Report

 

Posters, Presentations, Publications, and Other Materials

Our radar team has given presentations and posters at many different conferences and meetings. Below are a list of the posters and presentations given and a link to the file when available.

 

Presentations:

San Diego Zoo Invited Talk

Monitoring Our Migratory Birds Workshop Invited Talk - Ashland, WI

Review of Apple Blossom Wind Project Study

Review of LEEDCo Wind Project Study

NWCC Presentation

Region 3 Regional Office Presentation

Region 5 Regional Office Presentation

NYFO Presentation - 2011. 2012.

WI DNR and Public Service Comission Presentation

OH DNR Presentation

Great Lakes Wind Collaborative 2011

Midwest Fish and Wildlife Conference 2011

Great Lakes Bat Festival

Field Visits to Radar Units by USFWS NYFO and Iroquois NWR

ASPRS Midwest Region Annual Meeting Invited Talk

 

Posters:

NWCC Radar Project Summary

NWCC Bat Calls and Weather

Directorate Meeting

 

Publications:

USFWS. 2014. Great Lakes Avian Radar Seasonal Report for Huron and Oceana Counties, Michigan. Region 3 U.S. Fish and Wildlife Service.

 

Bowden, T.S. and J.K. Ferguson. In prep. A new tool to estimate survey volume of vertical scanning radars. Methods in Ecology and Evolution.

 

Heist, K.W., D.H. Johnson, and J.C. Gosse. In prep. Bat concentrations along shorelines of the Great Lakes. Conservation Biology.

 

Other Material:

Summary of Radar Project - Short Version (1 page) - Long Version (6 pages)

Acoustic Monitor Sign

GLRI Success Stories Book 2012

GLRI Success Stories Book 2013

 

Funding Provided For:

Avian and bat study on Eastern Lake Ontario Islands

Digitization of historical bird observations into the Midwest Avian Data Center which is part of the Avian Knowledge Network

 
Last updated: February 19, 2014