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RESULTS (in progress)

During mid-April through mid-June of 2016-2018, more than 5000 station-hours of nocturnal audio recordings were collected. Eight monitoring stations operated in spring 2016, four in spring 2017, and two in spring 2018. Table 1 indicates the span of monitoring at each station/year with the number of nights of data actually collected -- some nights were missed due to equipment malfunction.


71,739 high frequency bird calls (5-10 kHz) were extracted with the Tseep software, most from migrating warblers & sparrows. 20,000+ mid-frequency bird calls (2-5 kHz) were extracted with the Thrush software, the majority from migrating Catharus thrushes. Due to substantial & variable background noise in the mid-frequency range (primarily frog song), quantitative comparison of bird calling in this range between stations was not performed. Bird call analysis in this frequency band primarily targeted species information. The 5-10 kHz high frequency range had periods of low, relatively uniform, background noise. This enabled quantitative comparison of bird calls (primarily warblers & sparrows) during such quiet periods. These data are presented graphically via the linked sections below.


Background noise 2016

The primary source of background noise differences in the high frequency band were wind and surf. Background noise for the focused study period from May 3-4 through May 28-29, 2016 can be characterized as follows: There was a period with low surf and wind noise from May 3-4 to May 11-12. All stations had intermittent rain on the night of May 12-13. There was substantial surf and wind noise May 13-14 through the first hour of May 16-17, which included two nights with the strongest surf and wind noise of the focus period (May 14-15 & 15-16). From May 17-18 through 20-21 there was low surf and wind noise. From May 21-22 through May 28-29 there were three distinct wind/surf events (May 21-22; May 23-24 to 24-25; May 26-27 to 27-28).


Stations had varying susceptibility to surf and wind noise. Stations in close proximity to the coast had both surf and wind noise while inland stations only had wind noise. Table 2 indicates the quietest average background level night for each station and the extent each night's average background level in the focused study period was louder than the quietest level. The susceptibility of the three coastal stations to surf noise apparently was related to whether the microphone had direct line of sight to the surf and whether impediments such as coastal terrain, buildings and trees attenuated transmission of surf noise. Station 2 appeared to be the most exposed to surf noise and accordingly showed the highest nightly variance (SD; 7.03 dB) from its quietest night. It also had the night with the highest deviation in background level (May 14-15; 24.22 dB). Of the three coastal stations, Station 1 had the second highest nightly variance (SD; 5.49 dB) and for most individual nights consistently had the second highest deviation in background noise level. Station 3 had the least nightly variance (SD; 4.33 dB) and consistently lowest background level of the three coastal stations for any individual night. All three coastal stations had trees and bushy vegetation within 50-100 m and wind noise and, while not distinguished, was theoretically similar between these stations. The four inland stations (Stations 4-7) had lower nightly variance and lower background levels than the three coastal stations. Station 4 had deciduous trees in closest proximity and accordingly showed the highest susceptibility to wind noise with a standard deviation in nightly variance from its quietest night of 3.16 dB. Station 5 was the furthest from decidious trees and accordingly had the lowest nightly variance from its quietest night. While Station 7 data is challenging to interpret because of a microphone problem, its variance and levels from wind noise are estimated to have been similar to those of Station 4. Station 6 missed some nights of operation due to equipment problems but the data in Table 2 suggest it is between Stations 4 and 5 regarding background levels due to wind noise, but closer to Station 5.


Table 2 indicates that May 11-12 was the quietest night across the array, with four of the six stations equalling their quietest night during the focused study period. May 20-21 also appears to have been about equally quiet. The period May 3-4 to 10-11, except the night of May 7-8, is termed the first quiet period because the standard deviation of all station's average background level each night was less than 1 dB (see Table 2 SD1 column). 45/48 station/nights during this period had a deviation from quietest average background level of less than 1 dB. Of the four station/nights that were greater than 1 dB, three were less than 1.12 dB and one night at Station 2 (May 8-9) was 2 dB. The period May 17-18 to 22-23, except May 21-22, is termed the second quiet period because the standard deviation of all stations' average background level each night was less than 1 dB (see Table 2 SD1 column). 23/27 station/nights during this period had a deviation from quietest background level of less than 1 dB.  The four station/nights that were higher than 1 dB were all at Station 2 and ranged from 1.02 - 2.04 dB. Figs. 10 graphically shows the nightly background noise levels for each station during the first & second quiet periods. Fig. 10c shows a comparison of the intra-station standard deviation of nightly background sound level for each station. This latter graph reveals that the inland stations (4-6) generally had lower standard deviations of average background levels than the coastal station (1-3) even during the quiet periods.


Background Noise 2017    Background Noise 2018


Quantitative comparison of calling between stations


Fig. 1a-e show nightly calling totals for 2016-2018.


Fig. 2 and Table 3 show the seasonal differences in warbler & sparrow calling for 2016-2018.


Fig. 3a-d show quantity of warbler & sparrow calling by distance from Lake during the two quiet periods.


Figs. 4


Species composition

So far in the study, 22 species listed in New York as Threatened (3), Special Concern (5), or Species of Greatest Conservation Need (SGCN) have been detected. A number of other species detected are quite rare in the region of the study (i.e., Barn Owl, LeConte's Sparrow). Audio evidence, data, and discussion about these listed and rare species are presented at the following link: Rare Species. Species & quantitative information for calls detected in the high frequency band in spring 2016 (primarily warblers & sparrows), are available in a "Vesper" spectrograph & audio archive (~28,000 calls) searchable by station, date and species. Similar 2017 & 2018 data are still in analysis.


The all-night audio recordings (wav files) from this study (2016-2018; ~1.5 terabytes) are available by contacting Bill Evans (ear2sky at oldbird dot org) - a labor, media, and archival fee is involved.