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Published on August 24, 2022

Calling All Volunteers: Fall Migration Survey Data Needed

By Dr. Charles Clarkson

Perhaps the most difficult time to census birds is during the period of fall migration. As birds that spent the breeding season in northern New England and Canada begin heading south, most lack the vibrant colors and do not produce the recognizable vocalizations that make them so easy to identify during the spring and summer. After the difficult task of raising and fledging chicks, the nonbreeding season is a period of self-maintenance for most birds that breed in the northern hemisphere. While on the nonbreeding grounds, birds focus on exploiting enough resources to manage their own needs, such as a molt of their feathers and procuring energy for the upcoming migration and breeding season. They no longer select and defend territories, attract mates or spend their days tending young. Therefore, many birds are cryptic in the fall migratory and nonbreeding seasons, trying their best not to stand out to predators as they slink quietly through habitats looking for food.

While drab plumages and lack of vocal activity make birds far more difficult to detect and identify during this period, data on species diversity and abundance is no less important than during the remainder of the year, particularly if the goal of a (well-designed) management plan is to provide resources necessary to meet the full annual cycle of birds.

Fall Surveying

Over the course of September and October, fall migration surveys will take place across Audubon’s 14 publicly accessible refuges. Because of the increased skill required to collect accurate data during the fall, these surveys are generally conducted by highly trained and experienced biological technicians or Ornithologists. This fall, I will be performing migration surveys across our refuges and I invite you to participate in data collection as well. The task can be daunting, but with proper training and protocol, you can contribute meaningful data that will be helpful in the creation of our baseline dataset.

1 September to 1 November marks the period when the bulk of all migratory birds pass through the United States (, and this is the window in which we will survey these movements. While it would be ideal to spend every day performing surveys within this window, few of us have the time and energy to spend 61 consecutive days conducting fieldwork. Fortunately, migratory birds move in large pulses, with millions of birds passing overhead on evenings with ideal weather conditions and very few traveling during unfavorable weather. And, fortunately for us, analysis of meteorological and radar data has allowed us to create very detailed predictions about what birds will move and when.

BirdCast ( is a tool for tracking the migratory movements of birds across the U.S. The program is a collaboration between the Cornell Lab of Ornithology, Colorado State University and the University of Massachusetts, Amherst. The tools generated by BirdCast have made migration surveying an even more interesting pursuit. As the program creates graphs displaying migratory flights that have already occurred and maps predicting migratory flights to come, BirdCast allows us to not only monitor our state’s importance as a migratory corridor, but it allows us to collect data in a way that permits a form of ground-truthing. An assumption can be made that, on nights with large migratory flights overhead, the habitats below these “rivers of birds” should host a number of individuals the following day. As birds primarily migrate at night, birds land at dawn and their days are spent in forests, fields and wetlands refueling and awaiting the next favorable weather system for continued southern movements. During these periods of stopover, birds move laterally across the landscape, not confined to territories. Then, after foraging and resting during some period of time, birds take off and continue their southbound migrations.

By structuring our surveys to consider the natural history of the birds themselves and considering the data derived through BirdCast, we can maximize our chances of understanding bird migration in Rhode Island.

All of our 14 publicly accessible refuges will be surveyed for fall migratory birds this season (the list can be found on Surveys will be conducted during the mornings from 1 September to 1 November. As with our other surveys, we strive to make the job of the volunteer as simple as possible. Volunteers will be asked to collect meteorological data (wind speed, temperature, cloud cover), effort data (survey time and distance covered) and bird data. 

If you are interested in participating, we welcome your data. Your contribution can take one of three forms:

  1. Most detailed: data on species identities and total number of individuals
  2. Less detailed: data on avian taxa (warblers, sparrows, flycatchers, etc) and total numbers of individuals
  3. Least detailed: data on flock size estimates

Which of these data collection schemes you choose should be based on your confidence in identifying the species you are likely to encounter during your surveys. Simplistic data on total flock size without species identification is more useful than data containing incorrect species identifications. Keep this in mind when evaluating your fall migrant identification skills.

Before you sign-up to participate, consider the following:

  • Be honest about your fall bird identification skills. There are a number of obstacles to surveying fall birds effectively. First, most birds will occur in mixed-species flocks, where multiple individuals of multiple different species will be foraging together. It can be very tough to separate warbler species from one another when all individuals are drab and there is very little vocal activity. These flocks often move through the landscape in the forest canopy, making clear, unobstructed views of individual birds very difficult. Further, flocks tend to move quickly through habitats as they search out high-quality fuel for their migration and attempt to avoid predation. This necessitates rapid, accurate and confident identification skills on the part of the observer. If you are absolutely certain that you have the experience and skills necessary to collect accurate data on our fall migrants, we would love to have you participate in these surveys. Feeling like you can’t collect detailed data, but still hoping to contribute? Fear not, you still have a number of options:
    • Pair Up! There are a number of experienced birders that will be out collecting data for Audubon during the fall. Partnering with someone will help to strengthen your own id skills while allowing you to contribute data.
    • Collect less detailed data. As noted above, the data you report can take multiple forms. Simple reporting of the total number of flocks you encounter and an estimate of flock size is useful information to have. All are encouraged to participate in data collection, but it is imperative that the data reported are accurate, regardless of the form they take.
  • Plan to conduct a minimum of 3 surveys along the same route. Because bird turnover during migration is high, we cannot expect to capture this variability without visiting the same spot repeatedly throughout the season. For reference, during the state Bird Atlas, survey transects were visited between 13-15 times each fall. You should plan to visit your survey route as many times as you can during the survey window. Each visit can be timed to coincide with periods of high migration activity. You can determine these dates by regularly reviewing the migration prediction tools on Although the minimum number of visits to your survey route is three, the more surveys you can conduct, the better. Follow these guidelines to ensure you maximize your detections:
    • Survey when migration activity is highest. Using, focus your efforts on mornings after predicted migration activity is medium or high for the state. The fact that the information on the website is predicted out to three days enables you to plan ahead for mornings when surveys will be most fruitful.
    • Conduct surveys during ideal weather conditions. Sunlit mornings are the best time to conduct migration surveys. Although bird activity may be high during any weather, your ability to detect birds will be lower on cloudy and rainy days. Plan surveys for mornings when wind is low (high winds cause tree canopies to sway, which makes seeing and identifying birds very difficult) and skies are relatively clear. Your surveys should begin once the tree canopy is sunlit, as this is when activity will be highest (particularly on cold mornings) and your ability to see and identify birds will be maximized.

Survey Protocol:

Step 1: Identify which of our 14 publicly accessible refuges you would like to survey and your availability to conduct fall migration surveys. A list of our refuges can be found at

Step 2: Contact the Director of Avian Research to discuss your plans for contributing data ( Your survey plans (refuge, route and number of visits) and the type of data you will collect (most detailed, less detailed, least detailed) will be agreed upon.

Step 3: Prepare for your surveys by familiarizing yourself with the BirdCast website ( See the image gallery below for a quick guide (navigation buttons are below the images.)


Step 4: Perform your surveys. Contact the Director of Avian Research with any questions that might arise during the survey window (1 September – 1 November). See the image gallery below for a quick guide (navigation buttons are below the images.)


Step 5: Submit your data after the survey window ends on 1 November. Submissions can take the form of:

  • data sheets sent through the mail
  • a photo of the data sheets taken with your phone and submitted via email
  • data transferred to a spreadsheet (Microsoft Excel) and emailed.

General Survey Advice:

Relying on an app that identifies birds by vocal activity (such as Merlin) is not advised during fall migration surveys. Instead, a fair amount of time should be spent reviewing species identification tools prior to conducting a survey. Take time to learn about plumage types of fall migrating birds in the northeast and the difference in chip notes between species. Even with this advanced prep, it is still advisable to carry a field guide in the field that can be used to differentiate the species you come across.

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