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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 123, No. 1, March 2011 
TABLE 1. Cruise ship companies and number of large (>1,200 passengers) ships (and ship-nights 8 ) sailing in the 
Caribbean Sea during fall migration (Aug-Oct) 2003. 
Cruise ship company 
Number of ships 
Number of passengers 
Speed (knots) 
Number of ship-nights 
Royal Caribbean 
11 
2,020-3,114 
19-22 
777 
Carnival 
17 
1,452-2,974 
21-22 
1,267 
Princess 
6 
1,950-2,600 
284 
Celebrity 
5 
1,354-1.950 
21-24 
148 
Holland America 
5 
1,266-1.848 
22-24 
134 
Norwegian Cruise Line 
4 
1,748-2,400 
21-25 
147 
Disney Cruise 
2 
1,750 
224 
Totals 
50 
2,981 
Ship-night = sum of advertised nights of all cruises for all ships of each company. 
observed is representative of a typical fall night. I 
assumed the estimated kill for the single ship- 
night on 28 September was representative of the 
entire fall migration season simply to produce an 
approximate estimate of avian mortality to begin 
considering the impact of this additional anthro¬ 
pogenic structure. I also assumed the ship I 
observed was representative of other large ships. I 
only included large ships (>1,200 passengers) in 
my estimate of ship-nights to strengthen that 
assumption. Many smaller ships also sail the 
Caribbean during the fall season, but their deck 
arrangement and lighting patterns may be differ¬ 
ent from the larger cruise ships. 
DISCUSSION 
The Caribbean Sea is crossed by millions of 
neotropical migrants every fall. The decline of 
many of these species is of significant conservation 
concern. Perhaps even more alarming is the known 
presence of the endangered Kirtland’s Warbler 
(Dendroica kirtlandii ), the entire population of 
which must cross these waters during fall migration 
to reach wintering areas in the Bahamas. 
This issue warrants further investigation given 
the multitude of anthropogenic sources of avian 
mortality during fall migration and the additive 
nature of this mortality (Erickson et al. 2001). At a 
minimum, proper studies designed to estimate the 
magnitude and species composition of avian 
mortality on cruise ships during the fall migration 
period are warranted. Studies should address 
species-specific causal factors including light 
attraction, weather conditions, time of day and 
time of year. 
Efforts to work with the industry to minimize 
impacts would be prudent. If studies show lights 
are attracting birds, it is possible that alternative 
lighting options for these ships could reduce the 
impact on migratory birds. For example, light 
covers could prevent the light from illuminating 
skyward. This may eliminate the attraction to 
overhead migrating birds. Also, the wavelength of 
the light bulbs could be changed to be less 
attractive (Gauthreaux and Belser 2006). Flash 
pattern could also be manipulated to minimize 
attraction to night-migrating birds (Gauthreaux 
and Belser 2006, Gehring et al. 2009). Finally, 
most lights could be completely turned off after 
0200 hrs when the ships' daily activities are 
terminated. This could reduce by half the number 
of night-lighted hours on the ship. 
ACKNOWLEDGMENTS 
I thank R. P. Dettmers for an early review of the 
manuscript. C. E. Braun, C. S. Robbins, and an anonymous 
reviewer provided comments on the submitted manuscript. 
All provided valuable improvements. 
LITERATURE CITED 
Bullis Jr., H. R. 1954. Trans-Gulf migration, spring 1952. 
Auk 71:298-305. 
Erickson, W. P„ g. D. Johnson, M. D. Strickland, D. P. 
Young Jr., K. J. Sernka, and R. E. Good. 2001. 
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existing studies and comparisons to other sources of 
avian collision mortality in the United States. West 
Inc., Cheyenne, Wyoming, USA. 
Gauthreaux, S. A. and C. G. Belser. 2006. Effects of 
artificial night lighting on migrating birds. Pages 67- 
93 in Ecological consequences of artificial night 
lighting (C. Rich and T. Longcore, Editors). Island 
Press, Washington, D.C., USA. 
Gehring, J., P. Kerlinger, and A. M. Manville II. 2009. 
Communication towers, lights, and birds: successful 
methods of reducing the frequency of avian collisions. 
Ecological Applications 19:505-514. 
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