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THE WILSON JOURNAL OF ORNITHOLOGY . Vol 124. No. 4. December 2012 
duration of fieldwork might account for our 
relatively brief estimate of the Cozumel Vireo's 
nesting period (— 2.5 months) and observation 
of only one brood per pair. However, we predict 
that Cozumel Vireos may attempt multiple broods 
over a protracted season, as do some Caribbean 
vireos (e.g., Puerto Rican Vireo; Woodworth 1997 ) 
and some other passerines in the Yucatan region 
(e.g.. Black Catbird; JBL. ttnpubl. data). The 
incubation and nestling stages of the Cozumel 
V.reo were slightly shorter and longer, respective¬ 
ly, than those of the San Andres Vireo, but were 
close to those of other ‘eye-ring* vireos including, 
lor example, the White-eyed Vireo (incubation 
1995^ da ' VS ’ neSt, ' ng Stage: 9-11 da 7 S; Hopp ct al. 
The Cozumel Vireo is currently considered a 
spec.es of Least Concern (BirdLifc International 
2012), but insular taxa constitute a disproportion¬ 
ately large percentage of threatened bird species 
with declines frequently attributable to newly 
arrived predators and parasites (e.g., Blackburn 
et al. 2004). Vireos and their nests may be 
vulnerable to predation by boas and introduced 
mammals on Cozumel, but confirmation is 
needed. We detected no interspecific brood 
parasitism m the three Cozumel Vireo nests we 
observed. However, cowbird parasitism signifi¬ 
cantly affects several closely related vireos 
including, for example. Black-capped Vireo (V' 
wZTu 1 ]' f araSitized by B rown-headed Cow- 
birds (Molothrus ater) (Grzybowski 1995). and 
birds Vire °* parasilized b y Shi,i y Cow- 
birds (M. bonanensis) (Woodworth 1997) Recent 
expansion of Shiny Cow birds into the Yucatan 
represents a potential conservation threat for 
Cozumel Vireos (Kluza 1998). 
v b f h SiC natUral his, °^ data for Cozumel 
olher P 001 ^ k "own species will be 
crucial f 0r management decisions. Practical re- 
ITT are r aiSed h similarit 5' between the 
svm„ , tP V ' bainti and of the 
v - m ■ nmgister = I6 7_27s r> * c ” 
Orenstein 20,0) and belong to differemTubgen 
era, but more data are needed to develop criteria 
stedeTi b „T d b “ and «f the.,; 
species in the absence of adults. 
ACKNOWLEDGMENTS 
We thank Blanca Rolddn-Clarii. Felipe Judrez, and 
Rafael Chacon for logistical support in the field: I. 
Acosta-Rosado for assistance wilh plant identification: 
and C. E. Braun, C. C. Mineo. and two anonymous 
reviewers for comments that improved the manuscript. The 
Eundacidn do Barques y Museos de Cozumel. Fundacidn 
Plan Estrategico de Cozumel. Direcddn de Ecologia 
Municipal, and Island Endemics Foundation provided 
generous logistical support. We completed fieldwork in 
accordance with SEMARNAT permit #SGPA/DGVS/ 
03358/09 and Villanova University IACLC protocol #AS 
08-06. Villanova University and a Florida Ornithological 
Society William B. and Mary J. Robertson Fellowship 
awarded to JBL provided funding. This research was 
conducted while JEMG was a postdoctoral fellow at the 
Institiito de Ecologia. A.C. JBL dedicates this manuscripllo 
the loving memory of Thomas .1. Sullivan < 1922-2012). 
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