NatureBits

Migration Progress

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.

Graphs include data from both the Slingerlands site and Thacher Nature Center.

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Time of night

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.

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Presumed Species Recorded During Fall Migration 2009.

2010 Results to Come.

Results for Slingerlands are complete through October 15, 2009. Results for Thacher Nature Center are complete through October 1, 2009.

	Number of Calls		% of Calls
Species	Slingerlands	Thacher Nature Center	Slingerlands	Thacher Nature Center
Veery	54	71	1.7	1.3
Gray-cheeked Thrush	31	32	1.0	0.6
Swainson's Thrush	337	156	12.4	6.4
Hermit Thrush	14	21	0.4	0.3
Wood Thrush	17	10	0.4	0.3
Chestnut-sided Warbler	175	163	3.1	3.3
Cape May Warbler	12	9	0.4	0.2
Black-throated Blue Warbler	58	130	1.8	2.5
Bay-breasted Warbler	5	27	0.2	0.5
Black and White Warbler	12	17	0.4	0.3
American Redstart	61	89	1.9	1.7
Ovenbird	136	253	4.2	4.8
Northern Waterthrush	5	2	0.2	0.0
Common Yellowthroat	43	137	1.3	2.6
Wilson's Warbler	1	0	0.0	0.0
Canada Warbler	5	13	0.2	0.2
Chipping Sparrow	32	26	1.0	0.5
Savannah Sparrow	112	192	3.5	3.6
White-throated Sparrow	38	29	1.2	0.5
Swamp/Lincoln's Sparrow	5	30	0.6	0.5
Dark-eyed Junco	13	14	0.4	0.3
Rose-breasted Grosbeak	4	22	0.2	0.4
ZEEP group (see below)	895	1729	27.7	32.7
Single-banded up group (see below)	187	322	5.8	6.1
Double-banded up group(see below)	129	273	4.7	5.2
Single-banded down group (see below)	161	222	5.0	4.2
Double-banded down group (see below)	1	5	0.0	0.1

Some species, such as American Redstart, Chestnut-sided Warbler, and Ovenbird have distinctive calls and are relatively easy to identify. Unfortunately, the calls of many species (including some common ones) are too similar to calls of other species to be distinguished easily. These are presented as groups (e.g. ZEEP group.) The terms "single-banded up" etc. refer to the patterns seen on sonograms.

The ZEEP group includes the Yellow Warbler, Blackpoll Warbler, Magnolia Warbler, Louisiana Waterthrush, and Connecticut Warbler (unlikely). It also includes Cerulean Warbler and Worm-eating Warbler, but they are not expected at my locations.

The Single-banded Up Group includes Yellow-rumped Warbler (it also makes double-banded up calls) Blue-winged Warbler, Golden-winged Warbler, and White-crowned Sparrow. The counts may also include some Ovenbird calls that were unclear. Some birds in the group (Prothonotary Warbler, Swainson's Warbler, Clay-colored Sparrow, and Golden-winged Warbler) are not expected or are unlikely at my locations.

The Double-banded Up Group includes Yellow-rumped Warbler, Tennessee Warbler, Nashville Warbler, Orange-crowned Warbler, White-crowned Sparrow and Vesper Sparrow.

The Single-banded Down Group includes Northern Parula, Pine Warbler, Field Sparrow, and Vesper Sparrow.

The Double-banded Down Group includes Savannah Sparrow (which is distinct), LeConte's Sparrow, Nelson's Sharp-tailed Sparrow and Seaside Sharp-tailed Sparrow. All except Savannah Sparrow are unlikely at my locations. However, I have observed some double-banded down calls that do not seem to fit Savannah Sparrow, and I have included them in the Table as double-banded down.

Identifications and groupings are based on the CD-ROM "Flight Calls of Migrating Birds" by William R. Evans and Michael O'Brien." You can order the CD from Oldbird.org.

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How the recordings are made.

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 put up a microphone pointed at the sky. The mic output is either amplified and recorded directly to the hard drive of my computer or is recorded with a Song Meter autonomous digital recorder.

The bird calls are extracted from the sound file by using two free 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 result mainly from insect and amphibian calls). I separate the bird calls from the false positives by using GlassOFire (free from Oldbird.org). To identify species, I examine each call's sonogram by using audio editing software (principally Raven Pro), and I listen to some of the calls.

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 partially developed suburban area in Albany County, New York about 8 miles (13 km) west of the Hudson River at an altitude of about 320 ft (98 m). In 2009, I added a second recording system at the Emma Treadwell Thacher Nature Center which is located 7 miles (11.3 km) directly west of my home at an altitude of about 1325 ft (ca. 400m).

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