Do Migratory Birds Like It Hot?
AbstractWhy do birds migrate? Do all birds have the same reasons for migrating? Where do they go when they migrate? These are questions scientists have asked for centuries. The more species for which they gather data, the more specific the answers become. In this science project, you will choose a species to investigate, then access and evaluate real data collected by scientists to start answering those questions yourself!
ObjectiveDetermine whether there is a relationship between air temperature and where and when birds migrate.
Dr. Roland Kays, Dr. Stephen Blake, Sebastian Cruz, Dr. Wolfgang Fiedler, Dr. Bart Kranstauber, Carolina Proanio, Rolf Weinzierl, Dr. Martin Wikelski, and the MIGRATE NSF RCN, in conjunction with Sandra Slutz, PhD, Science Buddies
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Have you ever noticed that some of the bird species in your backyard disappear every winter and then reappear in the spring? Where do they go and why? This is a question that has intrigued people for centuries. In fact, discussions about the fate of migratory birds can be traced all the way back to Aristotle in ancient Greece! Aristotle proposed that the redstarts, birds that could be seen all summer, physically transformed themselves into robins during the winter. This idea, as crazy as it seems now, was taken as fact at the time. After all, the two species were not seen in the same area at the same time. But today, thanks to the work of bird watchers and scientists, we know that birds that appear and disappear from a specific geographical location are not transformed into other birds, but instead, are migrating.
The migration, or regular seasonal journey between two or more areas, takes birds from their breeding grounds to their wintering grounds, and then back again every year. For a migratory bird, life in the breeding ground centers on raising and protecting their young. The birds arrive there to find a mate, build a nest, lay eggs, and then feed and protect the offspring from predators. Then, as the seasons change, these migratory birds fly hundreds, or even thousands, of miles to their wintering grounds where they forage for food and store energy for the flight back to the breeding grounds. Some species also travel to additional locations. For example, many swans and ducks, like the common mallard, also journey to molting grounds. The molting grounds are safe locations with few predators and an abundant supply of food, where the birds stay while they lose their old flight feathers and grow new ones. Table 1, below, shows examples of several different migratory bird species and the journeys they undertake.
The Arctic Tern (Sterna paradisaea) makes the longest annual bird migration, traveling approximately 19,000 km (12,000 miles) each way between its Arctic breeding grounds and its Antarctic wintering grounds. (Photo by Estormiz, 2006.)
Even tiny birds, like hummingbirds, can fly many miles. The migration of the Ruby-throated Hummingbirds (Archilochus colubris) often includes a 500-mile nonstop flight across the Gulf of Mexico. (Photo courtesy of U.S. Fish & Wildlife Services.)
The Common Loon (Gavia immer) typically breeds on freshwater lakes, and winters in the ocean near the shoreline. (Photo by Cephas, 2009.)
The Swainson's Hawk (Buteo swainsoni) migrates across the equator twice a year to breed in North America and winters in South America. (Photo by Peter Wallack, 2007.)
Why do migratory birds undertake these journeys, and how do they find their way from one location to the next? These are questions that scientists are actively working to answer. To do so, they need to collect many different types of information. The most important facts to figure out are where the birds are, and when they are there. This type of information is called spatio-temporal data, where spatio refers to the space or location of the bird and the temporal information is the time (month, day, hour) that the bird was determined to be at that specific location. To collect this data, scientists put tags on birds. The three most commonly used tags to track migratory birds are: banding, global positioning system (GPS) tags, and Argos Doppler tags. More information about the advantages and disadvantages of the different tags can be found in the Science Buddies guide to Using Animal Tracking Data from Movebank for Science Projects.
When designing a study, the scientists decide which tagging method will best enable them to answer the specific question they're studying. All of the tags require a bird to be captured and the tag to be attached by a person for the first time. The video below shows how scientists physically tag birds.
Watch this video to see how scientists carefully attach a tracking device to a bird's back being careful to not injure the bird. Researchers are always careful to make sure the tag does not inhibit the animal's natural movements. (Video courtesy of Carolina B. Proano.)
Once scientists know the geo-spatial data, they can find out other information, like the weather, type of habitat, and food resources in the locations that are important to the birds. Collectively, this data can be used to investigate questions about why and how specific birds migrate.
In this science project, you will investigate how temperature influences a bird's migratory behavior. Do migratory birds have a preference for a specific temperature range? Do birds leave their breeding grounds to avoid cold temperatures? Do the breeding and wintering grounds have similar temperature ranges or is migration completely independent of temperature? To explore these questions, you will use real bird tracking data from Movebank. Movebank is an archive of animal movement data collected by scientists in the course of their studies. Many of these scientists have agreed to share their real data with Science Buddies for you to analyze. You will be using the same data that scientists are using in their own experiments!
Terms and Concepts
- Breeding grounds
- Wintering grounds
- Spatio-temporal data
- What birds in your area migrate?
- What kind of physiological changes occur between winter and spring for birds that don't migrate?
- How do scientists attach tracking tags to animals?
- What types of data do tracking tags give scientists?
Additional information about how bird migrations are tracked can be found at:
- Fiedler, W. (2009). New technologies for monitoring bird migration. Ringing & Migration. Volume 24, pages 175–179. Retrieved December 6, 2010, from http://blx1.bto.org/pdf/ringmigration/24_3/fiedler.pdf
More information about Movebank can be found at:
- Science Buddies. (2016). Using Animal Tracking Data from Movebank for Science Projects. Retrieved December 6, 2010, from http://www.sciencebuddies.org/science-fair-projects/project_ideas/movebank_tutorial.shtml
Help information for Google Earth can be found here:
- Google. (2010). Google Earth User Guide. Retrieved December 6, 2010, from http://earth.google.com/support/bin/static.py?page=guide_toc.cs
This website details earlier civilizations' explanations of bird migration:
- Armstrong, R. (n.d.). Ancient Explanations of Bird Migration. Retrieved December 6, 2010, from http://www.uh.edu/engines/epi2228.htm
These websites will provide you with more information about animal migrations:
- National Park Service. (2016). There and Back Again.... Retrieved September 2, 2016, from http://www.nature.nps.gov/biology/migratoryspecies/
- BBC. (n.d.). World On the Move: Great Animal Migrations. Retrieved December 10, 2010, from http://www.bbc.co.uk/radio4/worldonthemove/species/
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Materials and Equipment
- Computer with the following requirements:
- Internet access
- A spreadsheet program such as Microsoft Excel
- Where you are allowed to download a free version of the Google® Earth Pro software
- Lab notebook
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In this science project, you will download real bird migration and temperature data from Movebank.org. You will look at the migration route in Google Earth Pro and evaluate whether or not temperature plays a role in the species' migration.
Setting Up and Downloading the Migration and Weather Data
- To do this science project, you will need to install Google Earth Pro on the computer you are using. Google Earth is a program that allows you to map locations and look at satellite images of places all around the world. Be sure you have permission to download this from the computer's owner before you begin.
A free version of Google Earth Pro can be downloaded from https://support.google.com/earth/answer/176160?hl=en.
- You might find it useful to try one of the tutorials or to consult the Google Earth User's Guide to familiarize yourself with Google Earth Pro. The Google Earth general help page, earth.google.com/support/ is a useful starting point if you have questions about how to use different parts of the program.
- Before you start working with Movebank, you will have to create a free account to be able to access the necessary weather data for your project. To do this, visit Movebank.org. On the left site of the screen you will see a section called "User login". Click on "Create new account" and enter a username, your e-mail address, and name. After your registration, an email will be sent to you with your login information. Log into your account before you start your project to get access to all the data you need.
- Next, you will need to decide what species you are interested in studying for this science project. Table 1 shows a list of species that have available data sets suitable for this science project. Many additional species data sets on Movebank will also work for this project, but the ones listed in Table 1 are the only ones that have been tested.
|Species Name||Study Name|
|White stork (Ciconia ciconia)||MPIO white stork Argos|
|Barnacle goose (Branta leucopsis)||Barnacle goose (Svalbard)|
|Turkey vulture (Cathartes aura)||Turkey vultures in North & South America|
|Blackpoll warbler (Setophaga striata)||Blackpoll warbler eastern North America|
|White-fronted goose (Anser albifrons)||Migration timing in the white-fronted geese|
|Swainson's hawk (Buteo swainsoni)||Swainson's hawks|
Once you have decided on a species, go to the Tracking Data Map page in Movebank to access the bird tracking data. You will need the study name, listed in Table 1, to find the data. Or you can explore the other data sets available to you at Movebank and choose a bird species that most interests you. You can find more details on how this site works in the Movebank "Tracking Data Map" User Manual.
- If you want to find out more information about your chosen data set, you can browse the Studies page details for your selected study.
- Follow the instructions in the Movebank tutorial "Accessing data in Movebank" to download your data. Specifically, follow the instructions in the section "Downloading data in Movebank format." Keep all the default settings in the download window and choose "GoogleEarth (Tracks)" as the file type.
- Open the downloaded Google Earth file in Google Earth Pro. It will contain the path of each animal of your selected species on a map, complete with satellite images of each location. Examples of two migratory bird tracks are shown in Figure 1.
- You might find it useful to try one of the tutorials or consult the Google Earth Pro User's Guide to familiarize yourself with Google Earth Pro. The Google Earth general help page, http://earth.google.com/support/ is a useful starting point if you have questions about how to use different parts of the program.
- Once you have downloaded the tracking data, the next step is to access and download the annotated weather data for your selected study. You will do this by using the Env-DATA Track Annotation Service on Movebank. Instructions how to use this service can be found in the Env-DATA Tutorial on Movebank. You need to be logged into your Movebank account to get access to this information. Follow the instructions as given in the Env-DATA Tutorial and choose following parameters:
- Choose "Select animals" and "Select all" in the first pop up window, then click "Continue".
- In the next pop-up window you will select the environmental variables that you want to annotate. For this project, you are interested in the temperature data. Click on "Variables by type" and then the plus sign next to "Weather".
- Go to "Temperature" and choose "Air temperature."
- Then expand "ECMWF" and click on "Interim Full Daily at Pressure Levels." Select "Temperature" so that the box is checked. This variable should now be listed on the right side of the window under "Variable."
- Next, expand "Interim Full Daily at Surface" and check the box next to "Temperature (2 above Ground)." These data sets give temperature data at ground level for each location. These are the data sets you would want to download if you want to know what weather conditions an animal on the ground is experiencing.
- Both temperature variables should now be listed under "Variables."
- Click "Continue" and in the next pop-up window, keep the default settings for the Interpolation method (bilinear). Temperature data are available at various air pressures. For your ECMW Interim Full Daily PL Temperature, you have to choose a specific pressure level. Air pressure and elevation are linked. Choose an air pressure of 850 mba, which corresponds to an elevation of roughly 1.5 kilometers (km) and is a good approximation of the flight elevation for many birds. If you want to know the weather conditions a bird would experience during flight, these would be good data sets to download. Note: If this temperature data set is incomplete for your selected study, you can still continue the project with the ground level temperature data.
- Follow the instructions in the Env-DATA Tutorial to submit your annotation request and access your data.
Analyzing the Migration Path and Temperature Data
Once the Google Earth file has opened, you will see location points (dots) connected by migration tracks (lines). If you only see lines and no dots, double-click on the study name in your "Places" section in Google Earth Pro. Each animal in the study will have a single color. All the dots corresponding to the location of a specific animal will be the same color. In Figure 1, the migration paths of two birds are shown. One bird's data is color-coded orange and the other is color-coded blue.
- Note: The location points mark coordinates reported by the bird's tag. The tracks are generated by making the shortest possible line between the two location points that are closest together in time. The tracks are the "best guess" of the path the birds took, but only the location points are precise data.
Figure 1. Partial view, in Google Earth Pro, of the migratory track of two ospreys. The dots show locations where they were tracked using Argos Doppler tags. The lines connect temporally sequential locations in an approximation of the bird's flight path. (Data shown here was collected by Nye, P. and accessed through Movebank.)
- Using Google Earth Pro, look at all the tracks at once. You should see two geographic areas, connected by the tracks, that have a higher number of location points. These are the wintering and breeding grounds and represent the final destinations for the migrating birds.
- Which one is the breeding ground and which is the wintering ground? Clicking on a location dot opens a box of information about that data point. The top item in the box is a timestamp. The timestamp tells you when the bird's tag was recorded as being at that particular location. The information is given as year-month-date and time, in a 24-hour format. Determine which location is the breeding (summer) ground and which is the wintering ground, based on the months and when it is the "winter" season at each location.
- Do all of the birds in this study have the same wintering and breeding grounds? Depending on the species, they might or might not.
- Once you have identified the wintering and breeding grounds, you are ready to analyze the temperature data for individual birds. You will need to choose at least three representative bird tracks to analyze. Not all the tracks in a study might be good for analysis. Some tracks might have ended prematurely if the tag fell off the animal, if the animal died, or if the tag stopped functioning for technical reasons. Choose tracks that:
- Visually appear complete when compared to the other tracks in the study.
- Have location points whose timestamps span the duration of the study. Or, for a multiyear study, span at least one year, since these are annual migrations.
- Note: To look at an individual bird's data in Google Earth Pro, go to the menu on the left-hand side of your screen. Under "Places" you will see the study data. It will show your study name as "studyname.kmz". To see the different birds in the study, click the box with a plus (+) next to the study's name. Now you will see a separate ID or name for each bird. Click the box next to the bird's ID to select (box is checked) or un-select (box is un-checked) each bird. See Figure 2 for details. Bird tracks with selected (checked) IDs will be displayed on the map.
Figure 2. In this case, birds 3H and 3K are selected (checked) and their tracks are displayed on the map. Bird 3D is not displayed because its ID has not been selected.
- Choose one good bird migration track for analysis and look into the temperature data for that individual bird.
- Open the .zip file that you downloaded from you Env-DATA annotation request in step 5 of the previous section. It should contain one readme.txt file, which contains information about the data set, and a .csv file that includes your temperature data of your study. Open the .csv file in Excel.
- The spreadsheet will list the data for each data point in your study and should match the data you see in the information box for each data point in Google Earth Pro. The last two columns should contain the annotated temperatures that you requested ("ECMWF Interim Full Daily SFC Temperature (2 m above Ground)" and "ECMWF Interim Full Daily PL Temperature").
- Look at the temperature data for the bird that you have chosen. You can find it in the spreadsheet using its ID or name. In this case you are interested in the temperature the bird is experiencing during its migratory flight at a pressure level of 850 mba. Make a data table in your spreadsheet program, like Table 2, that for each month of one year shows the temperature the bird experiences, the temperature at the breeding ground, and the temperature in the wintering grounds.
- Note: Ideally your study should have tracking data for at least one full year. If it does not, choose a different study or take as many months as you have available in your study.
1 (January) 2 (February) 3 (March) 4 (April) 5 (May) 6 (June) 7 (July) 8 (August) 9 (September) 10 (October) 11 (November) 12 (December)
- From your timestamp column in your spreadsheet you will know when the temperature data has been recorded. If you do not see time information in this column, double-click in each cell of the timestamp column to convert the numbers into time information. Pick a representative temperature value from each month that is annotated to your selected bird and enter the value in your data table. More-advanced students can calculate the average temperature the bird experiences for each month. Note: The temperature data is recorded in Kelvin units. To convert these values into degree Celcius, you have to subtract 273.15 from the Kelvin temperature.
- To get the temperature data of your breeding and wintering grounds throughout the year, you will have to search temperature data from weather stations at Berkeley Earth.
- Select a data point from your bird track in Google Earth Pro that is in the wintering ground location of the bird you chose. From the data point information box, write down the latitude and longitude information ("Location Long" and "Location Lat").
- Enter these numbers into the Berkeley Earth website into the "Latitude" and "Longitude" boxes, then press "Location Search."
- From the list of weather stations, choose the one that has the shortest distance to the location you entered. Ideally, the date range of the weather data from this station should overlap with the data range for which your bird data was collected. For example, if the bird was tracked in the year 2014, you should also collect temperature data for the same year. If the date range does not overlap, you can pick the next closest weather station that has data for the right timeframe. If this station is more than 50 km away, select the closest station and use temperature data from a different year.
- Click on the name of your selected weather station. On the next page, below the first diagram "Raw Data relative to Expected Monthly Means," click on "Data Table," as shown in Figure 3.
- In the data table, you will find informaton about the weather station and a table with monthly temperature data for a certain time range. Search for the data that matches the year of your bird tracking data and write down the temperature for each month from column "Regional Temperature" in your data table. The temperature units in this table are degrees Celsius.
- Repeat steps a.–e. with the breeding ground location.
Figure 3. On the page for your selected weather station you will find the name (circled in green) and location (longitude and latitude, circled in blue) of the weather station. If you click on "Data Table" (circled in red) below the first diagram, you will get to the monthly temperature data for this weather station in a data table format.
- After you completed Table 2, use your spreadsheet program to make a line graph showing the bird's temperature, the temperature at the breeding grounds, and the temperature at the wintering grounds for each month.
- Temperature should be on the y-axis, and the month should be on the x-axis.
- There should be a total of three lines on the graph: one line each for the temperature at the bird's location, the wintering grounds, and the breeding grounds. The line representing the temperature that the bird is experiencing will overlap with the other two lines when the bird is at either the wintering or breeding grounds.
- Print out the graph and, below the x-axis, label the range of months that represent the bird breeding, migrating, and wintering.
- What temperature range does the bird experience? You can determine this by looking for the highest and lowest temperature points on the line representing the bird's temperature.
- What is the temperature range in the wintering location? What about the breeding location? How do the two compare? How do they compare to the temperature range experienced by the bird?
- Repeat steps 6–11 for at least two other good migration tracks.
- Based on all the graphs, what is the temperature range for the species?
- Based on your analysis, do you think temperature plays a role in this bird species' migration? If so, what is the role?
- If you write up this project for a science fair or school project, do not forget to credit the original authors of the Movebank data set!
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- Compare the Movebank temperature data for several species of birds. Do different species have different temperature tolerances? Can you draw any correlations between physical features of the birds and the temperature ranges in which they live?
- Extrapolate how climate change might affect the migration of your bird species. You will need to do some research about the various climate change models that exist and use them to predict future temperatures at the birds' breeding and wintering grounds. One place to start gathering information about climate change models is the United States Environmental Protection Agency's webpage about Future Temperature Changes.
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