Video dispatch given by Boonsri Dickinson. Birds migrate at night and use flight calls to communicate with each other. Andrew Farnsworth, an ornithologist at The Cornell Lab of Ornithology, has been recording the calls migratory birds make at night to keep track of their migration patterns. I went to visit Andrew on the west side of Manhattan. Andrew discovered that body mass might drive the variation in flight calls of different species. Some of the questions that remain are: Why do some species not even use flight calls? Are the flight calls related to other traits? Are flight calls learned? The problem is that unknown bird species identity and lack of information about the variation in the bird calls make it difficult to monitor bird populations. But Farnsworth is doing his best, and he described the challenges of analyzing the sounds in this episode of Bird Migration. Just because Andrew can record bird calls, it doesn't mean it's easy to make sense of all the auditory data that comes in. One of the difficulties lies in identifying bird species. Another difficulty is the lack of information about variation in bird calls, which makes it hard to monitor bird populations. Birds have unique sounds because genetics play a big role in what they sound like. During his research, Andrew discovered that the bird's body mass might drive the variation in flight calls in different species. Andrew told me that when we analyze certain species that are related, and how their acoustic signals are related (which means if the birds are related to each other genetically), they sound more alike. To help sort through the audio recordings, Andrew uses algorithms that can organize the calls and categorize bird species. In one of Andrew's research papers, I learned that the calls are generally in the 1-9 kilohertz frequency band and last about 50-300 millisecond in duration. It's worth noting that the flight calls are not the same as the songs and other short calls birds make such as chip notes and alarm calls. But today near the water, Andrew described his scientific approach to recording audio. I was surprised at how DIY it was. He also pointed out that to confirm what he's recording at night, it is important to document the birds people see during the day and where they see them. Citizen scientists can document their observations on a database called eBird. Bird migration gives us an idea of what's happening around the world and how our urban lifestyle affects birds' migratory decisions. Besides the obvious physical dangers of flying across the world, like getting eaten by a predator or getting lost in light pollution, other factors can affect the migratory paths of birds such as climate change. Why are weather patterns making birds migrate earlier than before? The timing of the migration is important because it indicates the health of the bird species and provides a sense of the state of biodiversity on our planet. The best part of the trip was spotting a bald eagle! I zoomed in so you could see it too! For more information on Andrew, check out his website: http://www.birds.cornell.edu/evb/Graduates_Andrew.htm And read more about his scientific lifestyle in a recent New York Times article: http://www.nytimes.com/2013/10/27/opinion/sunday/andrew-farnsworth.html?_r=0

• published: 08 Dec 2013
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