Before the Survey


Attend a workshop to learn the frog and toad species of the area, their calls, and the monitoring procedure. Workshops are offered in most Chicago wilderness counties, in February. Plan to attend a workshop each year that you monitor in order to brush up on your skills and learn of other amphibian or reptile monitoring projects that are happening.

Make a commitment to learn the frog and toad calls before the first survey. It is acceptable to bring a copy of the CD or your phone w/ the downloaded calls to help you identify what you hear. If you want to listen to the calls, please use ear buds or play the calls in the car, so that you do not encourage the real frogs to call.

You can download the calls of the native species at The Calling Frog Survey website, and listen to them on your phone or computer. In an effort to reduce waste, we encourage you to download the calls from our website. However, if you do not have a way to download the calls from a computer, CD recordings of frog and toads calls are available free of charge, by request, to active monitors. If you need a CD, please contact the Peggy Notebaert Nature Museum so that we may send you one (773-755-5107;

Establishing a Monitoring Route:

If you are a returning monitor, it is best for you to continue monitoring the same sites, or routes, as last year. Feel free to add new routes to your list if you want to do more.

For those who need to establish a new monitoring route, we will work with you after the workshops to do so. Once you attend a workshop, please fill out the program application form on our homepage with a short list of sites that would be convenient to you. We will work with the landowner agencies to help with site assignment based on which sites are not currently being monitored, and sites that are of high priority for scientific or land management reasons. If you have a particular forest preserve in mind, please check w/ your coordinator to see if it is available and appropriate for monitoring. Please note that site availability may be limited within the city of Chicago, based on the number of sites with appropriate habitat for frogs, or based on popularity of certain preserves. We will do our best to find a site that will be convenient for you.

Frogs and toads breed in ponds, swamps, lakes, etc., with a preference for temporary or semi-permanent waters. Although a temporary water body that usually dries up in a few months may appear to be a poor choice for breeding, it may in fact be an excellent choice because of the absence of tadpole predators such as fish.

Within your monitoring route(s), we recommend that you pick five listening points, or locations, for monitoring. If your site (route) is relatively small, then adjust the number of listening points accordingly. This will require one or two hours of your time on each night you monitor. If you choose more than five locations (listening points) you may not be able to sustain the effort in the future. It is important that you choose locations that are at least 200 meters apart. If you do not have a handheld GPS unit, the best alternative is your smart phone. Apple and Droid each have a free distance meter App that you can use to determine this distance accurately. If possible, try to include several habitat types (for example, a temporary woodland pond, or a marsh, or a shallow area of a lake) on your route.

Each land agency has it own procedures for allowing us night access to the preserves. You can learn the procedures by attending the workshop within the appropriate county.

Terminology – Route vs. location: Remember that we are using the term route to describe your overall site, or your entire monitoring area. We are using the term location to describe the individual listening points within each route. You may certainly choose more than one route, but please notify your coordinator if you do.

Roadside Monitoring:

In rural, mixed suburban-rural, and even some forest preserve areas it is possible to establish a route by driving down roads and spotting bodies of water, which are often less than a mile apart. The route you explore should have as little automobile traffic as possible so you have a good chance of hearing breeding calls later when you are monitoring. If you can safely park your car at or near a water body at night, you can monitor it. Pick a location (listening point) where you can listen for calls each time you monitor. That spot should be no more than 100-200 feet from the water in order to be able to hear weaker mating calls (i.e. from leopard frogs). If you must leave the roadside in order to get to the listening point, it is essential that you obtain advance permission of the landowner.

Routes in Completely Developed Areas:

In completely developed urban or suburban areas it is unlikely that you will be able to establish a roadside route. Although there are scattered stormwater retention ponds, corporate estate ponds, lawn ponds decorating newer subdivisions, and ponds or lagoons in city parks, most of the appropriate water bodies will be found in the forest preserves. It is best to use maps to locate water bodies within these heavily developed areas.

Finding the GPS coordinates for each of the locations (listening points):

When you record your data, you’ll need to write down the GPS coordinates for each monitoring location. The two best ways to do this are to use a hand held GPS unit or Google Earth on your smart phone. If you do not have access to either, and need to estimate the coordinates, please use the Internet sites that we discuss below.

Note: Enter the GPS coordinates as positive numbers. Our longitude is negative, but we include the W label to designate this.

To get coordinates w/o a phone or GPS unit:

  1. Find them by moving the marker on the map on the Locations page in the data entry website.
  2. You may also visit this website:
    Click on “Get Directions” in the upper left of the Google screen. In the box labeled “A”, type in your address or some other address that will get you to the Chicago region.

    • Click on button titled “Get Directions.” A thumbtack labeled “A” should appear on the map.
    • Drag the “A” thumbtack to a new location, and its GPS coordinates should appear in box “A” in the upper left.
  3. Other websites such as Google Earth also can find GPS coordinates for you. Please use decimal degree format if you are offered a choice – this looks like 44.4444, for example.

Conducting the Survey

Suitable Weather Conditions:

When suitable weather conditions for monitoring have arrived, time your arrival at the first location (listening point) so you can begin monitoring one half hour after sunset.

Suitable weather conditions for amphibians will generally be weather conditions deemed to be marginally suitable for humans. These include periods following a rain or periods of high humidity. Warmer days are good times for monitoring, especially in early spring. A Facebook Group, The Calling Frog Survey, is a good way to know if the weather conditions are right, so this can be a good way to judge when to go out.

Guidelines for Suitable Monitoring Weather
Period Minimum Air Temperature
(degrees Fahrenheit)
February 25 – April 20 45o
May 10 – May 30 55o
June 20 – July 10 65o

Note that these are guidelines. If the air temperature is a few degrees below the guidelines and the frogs appear to be actively chorusing, go ahead anyway. We have to make our decision on when to monitor on the basis of a weather forecast. However, the male amphibians may be stimulated to call on the basis of the water temperature. Once the sun has set, the air cools more rapidly than the water, and the frogs may still be responding to the heat of the afternoon. For this reason, air temperature is probably not the best indicator of calling activity. But measuring water temperature is something that can only be done upon arrival; and sometimes can’t be done at all if there is no access to the shoreline. If air temperature is not approaching the minimum suggested temperature, wait until it does, even if it is past the recommended date.

Beaufort Wind Scale:

Monitoring should not be conducted when the Beaufort wind scale exceeds 3. Strong winds will affect your ability to hear the calls of frogs and toads.

Beaufort Wind Scale Wind Speed (mph) Description
0 <1 CALM: smoke rises vertically
1 1-3 RELATIVELY STILL: rising smoke drifts, weather vane inactive
2 4-7 MODERATELY WINDY: leaves rustle, can feel wind on face
3 8-12 WINDY: leaves and twigs in constant motion, small flags extend
4 13-18 VERY WINDY: moves small branches, raises dust and loose paper (too windy to monitor)

Other Preparations:

Be sure that you are following any required access procedures. These vary from county to county. You will learn of any required procedures at the training workshops.

Bring the appropriate equipment — data sheets, rubber boots or old shoes, rain gear, camera (optional), phone (do not play calls as they may stimulate frogs to call), thermometer, pencils (more than one!), flashlight, GPS unit (optional), permit (if required in your county). If you are entering forest preserve land, a whistle (in case you and your partner become separated) and a cell phone are important aids.

Since you will be conducting these surveys in the dark, you are encouraged to bring an assistant along to share in the experience. This person can help you find the sites, document some kinds of information, and substitute for you in case of an illness.

Recording Weather Data:

The CFS 2024 DATA SHEET provides blank spaces for all of the necessary data:

At each listening point (route section), record the wind strength using the Beaufort wind scale.

At each location, record the time and measure air temperature (if you do not have a thermometer, use weatherbug or another free weather app on your phone).

At each location, note the percent cloud cover and choose the appropriate sky conditions category from the table on page 2 of your data sheet.

Note that if conditions do not change during the evening, you may use your initial wind scale, temperature, and sky conditions for your starting and ending conditions.

Weather history within the past 48 hours (rain and temperatures- above freezing or below freezing) should also be recorded.

Recording Optional Data

Optional additional information to note at each location:

  1. A general evaluation of water level in the wetland at the time of the survey (if possible).
  2. Any major changes to the breeding site since the previous survey.
  3. Any major changes to the habitats adjacent to the monitoring location since the previous survey.

Listening for Calls

Listen at each station for five minutes and record the Call Index (call intensity) for each species on the data sheet. If noise from traffic or other sources interferes with listening, extend the listening period for another five minutes.

Call Index Definitions
1 Individual calls can be counted; there is space between calls.
2 Some calls are overlapping; but individuals are still distinguishable.
3 Chorus is constant, continuous and overlapping; impossible to count individuals.
OB Indicate in the notes field, that a species was seen (observed), but not heard during the survey** This would be reported under “incidentals” in the database.

Difficult Species to Identify

Scientists involved with this project recommend that we report the two gray tree frog species generically as “gray tree frog” because of the known difficulty in distinguishing their calls. Volunteers must record the tree frog calls and send them to their county coordinator and/or the Peggy Notebaert Nature Museum ( for further identification. It is very important to include the air temperature (and water temperature if possible) when submitting your recording. This will help scientists determine which tree frog species you have recorded.

A number of other species are of special concern because of their rarity. If you think you have heard wood frogs, Fowler’s toad, cricket frogs, pickerel frogs or plains leopard frogs it is strongly recommended that you record the calls and/or take a photograph and submit as outlined above. Also, email or call your county coordinator and/or the Peggy Notebaert Nature Museum right away in order to give the scientists an opportunity to visit the site during breeding activity.

Any time that documentation of a species is made by photos or audio recordings, please denote under the “Comments” section of the datasheet.

After the Survey

Entering data:

The deadline for entering your data is August 31. Please do not forget to enter or send in your data – we can’t use it if we don’t have it!

The best way for you to enter your data is to use our online google form, at Data entry instructions are provided on the website, and you may also have received a copy at your training workshop. If you encounter difficulties with the site, do not hesitate to call The Peggy Notebaert Nature Museum ( for help! We can quickly get you back on track .

When you enter or send in your results, it is important to describe the route in a manner that will allow others to know precisely where your locations (listening points) are located and where the wetland is in relation to the location. The best way to do that is to describe your walking route and provide GPS coordinates for each location. It is very helpful to indicate landmarks, such as road intersections, streams, bends in roads, or buildings, and include their relations to the listening points.

Indicate the type of wetland; for example, is it a vernal pool (ie temporary pond), a pond in a wood lot, a marsh, a bog, a fen, a creek, a slough, a farm pond, a retention pond, a city park pond, etc.

We recommend that you draw a map of your entire route for your own use in getting from one stop to the next.

Very Important Final Notes:

Do NOT harass, take, or move any animals while monitoring. Do not play frog call recordings while conducting the survey. It is important to disturb the area as little as possible and to be aware that taking animals from forest preserves without a permit is punishable by law.

Please report any illegal activity related to rare animal or plant taking to your county coordinator or to The Peggy Notebaert Nature Museum (773-755-5107).

Any Questions?

Please don’t hesitate to contact Allison Sacerdote-Velat or your county coordinator with any questions you have. Or pose your question to the Facebook Group, The Calling Frog Survey.

Thanks for your help in conducting this survey and have an enjoyable field season!