The Wilson Journal of Ornithology 124( 1): 146-151, 2012 
AVIAN MORTALITY ASSOCIATED WITH A VOLCANIC GAS SEEP AT 
KISKA ISLAND, ALEUTIAN ISLANDS, ALASKA 
ALEXANDER L. BOND, 1 - 34 WILLIAM C. EVANS, 2 AND IAN L. JONES' 
ABSTRACT.—We identified natural pits associated with avian mortality at the base of Kiska Volcano in the western 
Aleutian Islands. Alaska in 2007. Living, moribund, and dead birds were regularly found at low spots in a canyon between 
two lava flows during 2001-2006, but the phenomenon was attributed to natural trapping and starvation of fledgling 
seabirds (mostly Least Auklets. Aethia pusilla) at a colony site with > I million birds present. However, 302 birds of eight 
species, including passerines, were found dead at the site during 2007-2010. suggesting additional factors were involved. 
Most carcasses showed no signs of injury and concentrations of dead birds had accumulated in a few distinctive low pits in 
the canyon. Gas samples from these locations showed elevated C0 2 concentrations in late 2010. Analysis of carcasses 
indicated no evidence of blunt trauma or internal bleeding. Volcanic gases accumulating at these poorly ventilated sites mas 
have caused the observed mortality, but are temporally variable. Most auklets breeding in the Aleutian Islands do so in 
recent lava flows that provide breeding habitat; our study documents a cost of this unusual habitat selection. Received I? 
March 2011. Accepted 28 September 2011. 
Active volcanoes frequently emit gases such as 
carbon monoxide (CO), and carbon dioxide (CO : ) 
from steam vents, I'umaroles, and gas seeps that are 
toxic in sufficient concentrations but odorless and 
therefore not repellent to animal life. Ecological 
effects of volcanic activity, including gas emissions, 
are of interest because of their potential effects on 
species at risk or with restricted distributions (e.g.. 
Short-tailed Albatross | Phoebastria alhatrus | breed¬ 
ing at Torishima; Einkelstein et al. 2010). 
There are 41 historically active volcanoes in 
Alaska, including 24 in the Aleutian Islands (Miller 
et al. 1998). The Aleutian Islands are also home to 
several million nesting seabirds (Byrd et al. 2005) 
and many species of land birds, including endemic 
subspecies and a vast array of migrants (Gibson and 
Byrd 2007). Least ( Aethia pit si I la) and Crested 
auklets </\. cristate!la) are two of the most abundant 
seabirds in Alaska, but most breed in large mixed 
colonies at seven sites in the Aleutian Islands—all in 
lava flows and associated debris on recently active 
volcanoes (Jones 1993a, b). Volcanically active 
areas, such as the Aleutian Islands, pose greater 
risks to birds than in many other areas. The eruption 
of Kasatochi Volcano in the central Aleutian 
Islands in August 2008 likely killed thousands of 
auklets (Williams el al. 2010), and two dead adult 
Fork-tailed Storm-Petrels (Oceanodromu J'urcata) 
Deportment of Biology. Memorial University 
Newfoundland, St. John’s. NL A IB 3X9, Canada 
'usT^' ^ Midd ' en ' ld R “ ad ' MC 
’Current address; Department of Biology. University 
Saskatchewan and Environment Canada I ZoZ 
Boulevard. Saskatoon. SK S7N 3H5. Canada 
Corresponding author; e-mail: aJex.bond<§>usask ca 
were found near a CCL seep one year following the 
eruption (J. C. Williams, pers. comm.) indicating 
that even non-breeding prospecting individuals are 
vulnerable. 
There arc few previous accounts of avian mor¬ 
tality specifically associated with volcanic gases 
(Lohkov and Nikanorov 1981. Durand 2007). Large 
and small mammals, and numerous bird species 
were found in 1974-1979 in a volcanic seep asso¬ 
ciated with Kikhpinych Volcano, Kamchatka. 
Russia. The authors inferred that mammals and 
large scavenging birds died of asphyxia alter 
entering a gas seep to scavenge smaller prey that 
had previously died of asphyxia (Lobkov and 
Nikanorov 1981). At least four adult Kelp Gulls 
(laims domimeanus) were likely killed by CCL or 
ITS emissions from geothermal vents at Sulphur 
Bay. Rotorua on New Zealand's North Island 
(Durand 2007). Dead seabirds without visible 
external injuries have been found in natural 
depressions similar to those on Kiska at Bogoslof 
Island, Aleutian Islands, Alaska. (J. C. Williams, 
pers. comm.). The objectives of our paper are to: 11 1 
characterize the gaseous emissions from Kiska 
Island, and (2) report the avian mortality observed 
from 2007 to 2010. especially that likely related to 
volcanic activity. 
METHODS 
Sirius Point. Kiska Island (52 08’ N. 177 36' E: 
Fig. I) is the site of a large seabird colony with ■ >| 
million Least and Crested auklets (Sowls et al. 
1978). The auklet colony is on the westernmost 
active volcano in the Aleutian Islands: Kiska 
Volcano. A parasitic lava cone emerged from the 
sea adjacent to Sirius Point in 1964-1969. forming 
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