The Wilson Journal of Ornithology 124(2): 265-269, 2012 
VEERTES EXPERIENCE MORE VARIED ACOUSTIC COMPETITION AT 
DAWN THAN AT DUSK 
KARA LOEB BELINSKY,' M JOEL. LAHMAN HOGLE, 1 2 * 4 AND KENNETH A. SCHMIDT' 
ABSTRACT.—We compared the amount and type of acoustic competition experienced by Veeries (Catharus 
fuscescens) when they sang in the dawn chorus as opposed to when they sang in the dusk chorus. Veery songs tended to be 
masked more often at dawn than at dusk. Veery songs were masked 2.4 times per 10-song sequence at dawn and 1.2 times 
per 10-song sequence at dusk. A larger number ot species were responsible lor masking that occurred at dawn. At least 12 
species masked Veery songs in our sample, and all identified species masked at dawn; only seven ol the 12 also masked at 
dusk. These results represent the first empirical data documenting natural differences in acoustic competition at dawn and 
dusk. Acoustic competition may help explain why. in addition to singing at dawn. Veeries and other thrushes also have a 
pronounced dusk chorus. Received 7 July 2011. Accepted 22 December 2011. 
Birds and other animals that use sound to 
communicate have the challenge of competing 
acoustically with other sounds in their environ¬ 
ment (Bradbury and Vehrencamp 1998, Wiley 
2006, Brumm and Naguib 2009). Signalers 
experience acoustic competition when other 
sounds mask or overlap their signal both in 
frequency and in time (Klump 1996, Slabbekoorn 
2004). Acoustic competition decreases the effi¬ 
ciency of communication for both signalers and 
receivers by making signals more difficult to 
detect and decode (Wiley 2006). For example, 
Zebra Finches (Tacniopygia gititata ) and Budger¬ 
igars (Melopsittucus urululatus) exhibit reduced 
responses to conspecific song in the presence of 
background noise (Dent et al. 2009). Background 
noise also impedes communication in many other 
animal taxa (fish, insects, frogs; Samarra el al. 
2009. Belanger et al. 2010, Richardson and 
Lengagne 2010). 
Any sound in the environment can disrupt 
acoustic communication (Brumm and Naguib 
2009). Traffic noise anil other anthropogenic 
sounds can hamper signaling in urban areas 
(Slabbekoorn and Peet 2003. Patricelli and 
Blickley 2006, Warren et al. 2006). Abiotic 
sounds, including those caused by wind and 
water, can also cause acoustic competition, and 
Common Chaffinches (bringilia coelebs) have 
been shown to use different song types near loud 
streams (Brumm and Slater 2006). Another source 
1 Depunment of Biological Sciences. Texas Tech Uni¬ 
versity. Lubbock, TX 79409, USA. 
Biology Department, Earl ham College. Richmond. IN 
47474, USA. 
'Current address: Biology Department. Arcadia Univer¬ 
sity. Glenside. PA, 19038, USA. 
4 Corresponding author; e-mail: belinskyk@arcadia.edu 
of acoustic competition is signals of other nearby 
animals, especially during peak times of activity, 
such as during the dawn chorus of birds (Klump 
1996, Staicer et al. 1996). Poesel et al. (2007) 
found high rates of masking by conspecific song 
may hamper eavesdropping among Eurasian 
Blue Tits (Cyanistes caemleus) during the dawn 
chorus. Poll I et al. (2009) recently tested the 
ability of Greal Tits (Pants major) to detect 
simulated conspecific songs during simulations of 
urban, woodland, and dawn chorus background 
noises. These researchers found that while all 
three types of background noise reduced birds' 
detection of the simulated conspecific signal, the 
dawn chorus had the strongest deleterious effect. 
The difficulty of communicating in a group of 
signalers has been referred to as the ‘cocktail 
party problem' (Bee and Micheyl 2008). The 
acoustic competition caused by groups of closely 
related signalers, such as birds singing in the dawn 
chorus, may be particularly problematic because 
competing signals often occur in similar time and 
frequency ranges (Klump 1996). Acoustic com¬ 
petition from conspecifics may also interfere with 
communication, although this situation is compli¬ 
cated us some overlapping vocalizations may 
signal aggression (Naguib and MenniU 2010). 
Birds have adapted to the cocktail parly of the 
dawn chorus in several ways. Some species have 
been shown to adjust the short-term timing of 
their singing to avoid overlap with the songs of 
other species (Popp et al. 1985, Knapton 1987, 
Brumm 2006). Naugler and Ratcliff (1994) found 
American Tree Sparrows ( Spize/la arborea) used 
fewer song types in populations where fewer other 
species were singing. Few studies, however, have 
examined natural differences in the amount and 
type ot acoustic competition experienced by birds. 
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