Many species of birds make flight calls while they migrate during the night, and I have been recording these calls to follow the fall migration. Here are some of my results.
Last updated 31 October 2007.
The high-frequency calls (red-brown bars) are usually made by warblers and sparrows.
The mid-frequency calls (orange bars) are made by thrushes and a number of other birds such as rose-breasted grosbeak and scarlet tanager.
No recordings were made from Sep 25 through Oct 1. Other nights are blank usually because I did not record during rainstorms or when thunderstorms were threatening. I shut the system down on October 31, as it had detected no birds during the last dew nights.
Because of the large scale, a nightly record of one or two calls barely shows on the graph.
These two graphs show the times of night when high-frequency and mid-frequency calls were recorded. The mid-frequency calls are plotted as hours before sunrise to make clear the increase in thrush calls in the hour or so before dawn. The high frequency calls are characteristic of warblers and sparrows and the mid-frequency calls are made by thrushes and other mid-size birds.
Return to topIt's time consuming to check so many calls (and I've been doing other things, too), so I'm waaaaay behind on identifications. If there is a missing date on the table below, I haven't done enough with the data to report anything.
I have based my identifications on the CD-ROM "Flight Calls of Migrating Birds" by William R. Evans and Michael O'Brien"
Some species, such as American Redstart, have a distinctive call and are fairly easy to identify confidently. Unfortunately, the calls of many species (including some common ones) are too similar to other species to be distinguished easily. I'm still learning, so I've identified only the relatively easy ones.
| Night | Presumed Species Identified |
|---|---|
| August 12-13 | Ovenbird(2), American Redstart(1) |
| August 13-14 | American Redstart(4), Chestnut-sided Warbler(8), Bay-breasted Warbler(1), Ovenbird(1) |
| August 14-15 | Hermit Thrush(4), Veery(2), American Redstart(1), Ovenbird(2), More to come |
| August 20-21 | Veery(37) More to come |
| August 22-23 | Hermit Thrush(7) More to come. |
| August 26-27 | Killdeer, Veery (1), Wood Thrush(4), American Redstart(1), Lousiana Waterthrush(1), More to come |
| August 27-28 | Killdeer, Cape May Warbler(1), Ovenbird(1), More to come |
| August 28-29 | Killdeer, Chestnut-sided Warbler(1), Black-throated Blue Warbler(2), Ovenbird(3),Rose-breasted Grosbeak(3), Savannah Sparrow(1), More to come |
| August 29-30 | Killdeer, Veery(1), Ovenbird(1), Rose-breasted Grosbeak(1), More to come |
| August 31 -September 1 | Veery(6), Chestnut-sided Warbler(1), Black-throated Blue Warbler (1), Savannah Sparrow(1), More to come |
| September 1-2 | Veery(9), Chestnut-sided Warbler(1), American Redstart(1), More to come |
| September 2-3 | Veery(3), Hermit Thrush(1), Swainson's Thrush(2), Wood Thrush(1), Black-throated Blue Warbler(1), Black-throated Green Warbler(1), Wilson's Warbler(2), Common Yellowthroat(1), Bay-breasted Warbler(2), More to come |
| September 18-19 | Swainson's Thrush(18), Unidentified (6, includes 5 possible Swainson's Thrush),More to come |
For a detailed description of how to set up and record avian flight calls go to Oldbird.org. My system is adapted from theirs.
Basically, I have placed on the roof of my home a directional microphone pointed at the sky. The mic output is amplified and the sounds are recorded directly to the hard drive of my computer.
The bird calls are extracted from the sound file by using two software programs, Tseep-x and Thrush-x, which were obtained from Oldbird.org. Tseep-x extracts short high frequency calls (6,000 - 10,000 Hz) which are produced by warblers and sparrows. Thrush-x extracts mid frequency calls (2,800 - 5000 Hz) which are produced by thrushes, rose-breasted grosbeak, tanagers and other species. Each of these programs produces many false positives (which seem to result mainly from insect and amphibian calls). I separate the bird calls from the false positives by using GlassOFire (Oldbird.org). To identify species, I listen to each call and examine its sonogram by using audio editing software (principally SoundForge or Raven Lite).
I record the calls from one-half hour after sunset to one-half hour before sunrise (weather and my schedule permitting). My home is located in a semi-rural area in Albany County, New York about 10 miles (16 km) west of the Hudson River at an altitude of about 320 ft (ca. 100 m).
The CD-ROM "Flight Calls of Migratory Birds" by William R. Evans and Michael O'Brien can be obtained from Oldbird.org.
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