Tests of two functions of alarm calls given by yellow warblers during nest
defence
Sharon A. Gill and Spencer G. Sealy
Can. J. Zool./Rev. Can. Zool. 81(10): 1685-1690 (2003)
During nest defence, yellow warblers (Dendroica petechia) give "seet" and
"chip" calls. Seet calls are given preferentially toward brood parasitic
brown-headed cowbirds (Molothrus ater) during the yellow warblers'
egg-laying period, whereas chip calls are given toward mammalian and avian
nest predators throughout the nesting period. In this study, we investigated
two possible functions of seet and chip calls during nest defence by playing
alarm calls to nesting yellow warblers. We tested whether nest owners give
seet and chip calls during defence to alert their offspring and their mates
about nest threats and, in the latter case, whether the alarm calls differ
in function depending on nesting stage. In response to playbacks, nestlings
remained inactive for a significantly longer period when chip calls were
played than when seet calls were played. Female yellow warblers returned to
their nesting areas more quickly when seet calls were played than when chip
calls were played, but pairs were equally likely to return to the nesting
area in response to both call types. These findings suggests that both seet
and chip calls alert mates but that only chip calls function to alert
nestlings of potential danger.
>From Fri, 30 Apr 2004 11:35:38 -0700
From: adam frankel <>
To:
Date: Fri, 30 Apr 2004 11:35:38 -0700
Subject: Bioacoustics articles, Can. J. Zool.
Message-Id:
decline and applications for breeding bird surveys
Silke Nebel, Brian J McCaffery. Canadian Journal of Zoology. Ottawa: Oct
2003. Vol. 81, Iss. 10; pg. 1702
Abstract
We documented vocalization activity of breeding shorebirds at two sites in
northern and western Alaska, on the Colville River Delta and on the Yukon -
Kuskokwim Delta. At both sites, number of calling individuals decreased
throughout the season. Variation in vocalization activity was significantly
higher at the Colville River Delta towards the end of the season, while
weather variables affected vocalization activity only on the Yukon -
Kuskokwim Delta. Our results highlight the importance of timing, weather,
and site-specific attributes on number of birds detected. We discuss our
findings in the context of different methods to monitor breeding shorebirds.
Effect of underwater seismic surveys on molting male Long-tailed Ducks in
the Beaufort Sea, Alaska
Deborah L Lacroix, Richard B Lanctot, John A Reed, Trent L McDonald.
Canadian Journal of Zoology. Ottawa: Nov 2003. Vol. 81, Iss. 11; pg. 1862,
14 pgs
Large numbers of Long-tailed Ducks (Clangula hyemalis) (10 000 - 30 000)
undergo a postnuptial wing molt along barrier islands of the Beaufort Sea,
Alaska. To investigate the potential effects of underwater seismic
activities on this species, we monitored the number and diving behavior of
molting Long-tailed Ducks before, during, and after seismic activities in a
seismic area and two
control areas nearby between uly and September 2001. Aerial surveys
documented a decline in duck numbers in both seismic and control areas
during the period of seismic activity. We used automated data-collection
computers to monitor the presence and diving behavior of radio-equipped
Long-tailed Ducks residing within 2.5 km of a series of computer setups
located along the barrier islands and on the mainland. A statistical
analysis based on a modified before-after control-impact approach found no
difference in indices of site fidelity or diving intensity between the
seismic area and two control areas. Thus, we found no effect of seismic
activity on movements
and diving behavior of molting Long-tailed Ducks. These results should be
evaluated carefully, however, as logistical and ecological factors limited
our ability to detect more subtle disturbance effects. We recommend
additional studies on other bird species to fully
understand the effects of underwater seismic testing.
Richardson's ground squirrels (Spermophilus richardsonii) do not communicate
predator movements via changes in call rate
David R. Wilson and James F. Hare
Can. J. Zool./Rev. Can. Zool. 81(12): 2026-2031 (2003)
The call rate of repetitive alarm calls produced by Richardson's ground
squirrels (Spermophilus richardsonii) conveys the extent of threat during
predator encounters. It remains unknown, however, whether changes in call
rate communicate predator movements. That is, does an increasing call rate
indicate an approaching predator and a decreasing rate the opposite? We
presented free-living squirrels with moving predator models and recorded
their responses. Vigilant behaviour increased more when predators approached
versus retreated, suggesting that squirrels recognize the changes in threat
associated with predator movements. Squirrels rarely produced alarm calls
during these encounters, however, suggesting that squirrels do not rely
entirely on alarm ocalizations to assess the threat posed by potential
predators. Receivers of manipulated calls did not respond differentially to
alarm calls containing an increasing or decreasing rate of syllable
production. Thus, while rate may encode information about the extent of
threat, Richardson's ground squirrels do not communicate predator movements
via changes in call rate.
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