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THE WILSON JOURNAL OF ORNITHOLOGY • Vo/. 124. No. 2. June 2012 
although the cocktail party problem may vary in 
intensity For example, some but not all bird 
species are believed to have a peak of singing at 
dawn and another at dusk, although the dawn and 
dusk chorusing behavior has been quantified for 
only a few species (Staieer et al. 19%, Slabbe- 
koom 2004, Catchpole and Slater 2008). Since 
only some birds sing at both dawn and dusk, the 
amount and type of acoustic competition may 
differ between the dawn and dusk choruses. 
Vecries (Car ha ms fuscescens) are a passerine 
species with acoustically complex songs that sing 
at both dawn and dusk (Samuel 1972; KAS and 
KLB, unpubl. data). Veery songs have relatively 
wide frequency ranges, and include several 
phrases featuring simultaneous frequency bands 
with rapid frequency modulations (Samuel 1972, 
Weary et al. 1986). Acoustically complex songs’ 
such as those of the Veery. are thought to degrade 
rapidly in the thickly vegetated forest habitats 
where Vecries sing (Wiley 2006), and their songs 
are likely to be vulnerable to masking by other 
species. Vecries and many other members of the 
Turdidae are known to have peaks of singing 
activity at both dawn and dusk (Samuel I97"> 
siagsvold 1996. Ball 2000. Rivers and Kroodsma' 
2000). Veeries will encounter more acoustic 
competition at dawn than at dusk, if many of the 
other species that share habitat with Vecries sine 
at dawn but only some also sing at dusk. Our 
objective was to test this prediction by comparing 
the amount and type of interspecific vocal 
masking that Veeries experience during dawn 
and dusk choruses. 
METHODS 
We recorded samples of natural Veery singin 
rom a color-banded population at the Car 
Institute of Ecosystem Studies in Dutchev 
County, New York, USA from mid May to lat 
June in 2009 and 2010. The -325-ha Car 
Institute property (41 50’ N. 73 45' W) i 
dominated by a second-growth oak (Quercus spp 
and maple (Acer spp.) forest with paths, trails an 
ephemera 1 wetlands throughout. Common bird 
habiting the wooded areas include Ovenhird 
;. w/uv at,roc “PMoh American Robins (Turd,, 
mi gra,orius), and Wood Thrushes (HvlocZ 
ZT (KAS. unpubl. data). Wc S fo 
Zn Td P du S sk ° f h VeCry * h « ,n * "uri" 
sunrise and sunse,. We recorded sanies ofV^ 
song using a Telinga parabolic reflector, a Senn- 
heiser MKH 62 microphone, and a MaranlzMPD 
000 digital recorder (sampling rate of 44.1 kHz.bit 
rate of 705.5 kbps). This equipment allowed us i 
collect high-quality directional recordings th.i: 
focused on the song of the focal bird in a way that 
approximates how a receiver (perhaps a potential 
mate or rival) would be listening. We fixtusdon 
collecting the best-quality recordings of Veery song 
that were possible (at close range, which is 
challenging with such visually and bebaviorally 
cryptic birds) w ithout reference to die singing of 
other species. 
We selected 34 dawn and 34 dusk recordings to 
analyze based entirely on the spectrogram quality 
of Veery songs in the recording (high signal to 
noise ratio), We used observations of color band- 
singing locations, and spectrographic comparisons 
ot song types to ensure that each sample in each 
ol our dawn and dusk pools of recordings came 
trom a different male. Nine males were recorded 
both at dawn and at dusk, while 25 males were 
recorded only once, either at dawn or dusk. Wf 
discarded any recording that included songs from 
more than one Veery because countersinging is 
olten characterized by higher song rates, which 
would shorten the time available for heterospe- 
eilie masking, possibly biasing our measurements 
We found conspeeific masking by Veenes was 
relatively rare, possibly because Veeries have 
large territories and because individual males 
appear to only sing at specific intervals during the 
breeding season (KLB and KAS. unpubl. data' 
Spectrogram analysis was conducted vwtb 
Raven Pro 1.4 (Cornell Laboratory of Ornitholo¬ 
gy- Ithaca. NY. USA). We selected a segment 
from each recording containing the 10 consecu¬ 
tive songs of the highest quality for analysis. 'V 
standardized the amount of Veery singing that -* e 
sampled by analyzing a subset of 10 songs ft® 01 
our dawn and dusk recordings. We have r.oi 
noticed a difference in the amount or rate of 
singing by Veeries at dawn and dusk but. because 
wc have not measured this explicitly, we decide 
to control for the possibility that the amount of 
singing might differ. 
We counted the number of Veery' songs dwt 
were masked by another species’ song in each 10- 
s°ng segment. A song from the focal male was 
considered masked if any heterospecific avian 
vocalization measuring 75 db or above (measured 
using Raven s average energy measurement !t"’l 
overlapped it in frequency and time (Fig- D- We 
