Forecast and Analysis

Lights Out in October (well…always!)

Diya Balagopal Guest Authors Oct 03, 2023

The BirdCast team has a growing number of friends and family members, and for today’s post, a new face is featured! We introduce Diya Balagopal, a high school sophomore from Frisco, Texas driven by a love for birds and the environment. She has a strong interest in data and computer science, looking ahead to a career in which she can merge technology with conservation. And, nearly singlehandedly, Diya successfully campaigned for Frisco, Texas to adopt a lights out proclamation (which they did this spring)! Success in conservation and awareness may take a village, but times and again we see success at the hands of the individual! Take it away, Diya!


The BirdCast team has supported lights out initiatives with peer-reviewed research and tools to visualize bird migration as the groundswell of programs and initiatives around the US seeking to minimize and to eliminate the risks light pollution poses for nocturnally migrating birds continues to grow. The website and alerts provide information about bird migration intensity and the areas where such intensities are predicted to be locally high to keep you informed about the nocturnal bird migration traffic in the US and where and when (and even how) you can turn out lights to protect nocturnally migrating birds. 

As is typical for the September weeks of the fall migration season, we’ve been monitoring a trend that saw increasing numbers of birds on the move over some areas of the contiguous US, with a high traffic rate observed in both the northeast and northwest regions. We saw several large bird migration events during the month, with an estimated 170 million to 630 million birds flying through the United States each night from September 21 – 26, 2023. We also highlight another night – September 17, 2023 – when an astonishing 709 million birds took flight across the United States. 

This awe-inspiring natural phenomenon showcases the remarkable journeys these birds undertake and the jaw-dropping numbers of birds involved in these movements. During the fall migration season, we typically observe patterns of birds detected by weather surveillance radar appearing in late July and early August. These patterns are often subtle, given the large numbers of insects also flying during these summer periods. However, birds begin to dominate the airspaces from our radar perspective as August turns to September, and by this point in the fall, very large movements of birds are occurring and dominating the patterns we see in radar data.

What makes the present, mid-September period particularly fascinating is the gradual shift in migration concentration we see within a night among regions. As night progresses, and especially as several nights progress, we observe a pulse of migration moving  from north to south. This shift is not unusual, as it aligns with the seasonal movements of a diverse array of bird species. For example, bird migration patterns from September 21th to September 26th are highlighted in the animation below, with mosaics showcasing the nightly bird migration at 00:00 ET, a time that often captures the largest number of birds migrating across the continent. 

To get a closer look at this remarkable event on the night of September 17, check out the animated map below. Although migration intensity is minimal in many areas east of the Appalachians and in the northern Great Plains, extensive medium to high intensity flights occurred from the Great Lakes through the southeastern and south central US. Whereas the majority of birds are migrating southward, as indicated by the arrows depicting the direction to which birds are moving, it’s worth noting subtle variations in their migration paths, such as those differences between birds in the southeastern US and the south central US

Here we have the three-day forecast maps for tonight, tomorrow, and the following night.

Here are the Lights Out Alert Maps from CSU AeroEco for the same time frame. These maps indicate areas – in red – where it’s crucial to turn off lights during these nights.

Stay tuned during the month of October as we continue to highlight Lights Out Nights forecasts to support bird conservation by reducing nighttime lighting during migration season. The small act of turning off lights can make a big difference for our feathered friends!