The Wilson Journal of Ornithology 1 24(4):743-749, 2012 
FIRST DESCRIPTION OF THE NEST AND EGGS OF THE ISLAND- 
ENDEMIC COZUMEL VIREO, VIREO BAIRD/ 
JOSHUA B. LAPERGOLA, 14,5 JESUS GUSTAVO MARINA HIPOLITO, 2 
JUAN E. MARTINEZ-GOMEZ.' AND ROBERT L. CURRY 1 
ABSTRACT.—We report the lirsi description of the nest, eggs. ;md nesting phenology of the Cozumel Vireo {Viren 
herd,), a passenne species endemic to Isla Cozumel. Mexico. We discovered three nests of this species in 2009 These open- 
cup nests were woven onto branches and hung beneath forks. Clutch size was 2-3 eggs, and eggs were ovate and had a white 
ground color with reddish-brown Hecks. These characteristics of nests and eggs are similar to those of most other Vireo spp 
including other West Indian members of the Vireo subgenus. Breeding activities, including egg-laying, incubation and 
nestling and post-fledging provisioning occurred from May to July 2009. We estimated the length of incubation to be -14 days 
and length of the nestling stage to be 11-12 days. Much of the Cozumel Vireo’s breeding biology remains unknown and 
further study of this single-island endemic is needed. Received 25 Mon h 2012. Accepted 6 July 2012. 
The vireos (Vireonidae) comprise 32 species 
that range from North to South America, includ¬ 
ing many islands (Brewer and Orenstein 2010). 
Vireo. largest of the family’s four genera, contains 
31 species with —61% mostly or wholly restricted 
to tropical latitudes including the nine species 
restricted to islands (Raffaele et al. 1998. Brewer 
and Orenstein 2010). A temperate-zone bias (cf. 
Stutchbury and Morton 2001 j characterizes 
knowledge of the breeding biology of vireos: 
species nesting in Canada and the United Slates 
are overall better known than neotropical and 
Southern Hemisphere counterparts. The nests and 
eggs of several vireos breeding in Mexico and 
Central and South America remain undescribcd 
iBrewer and Orenstein 2010). 
fwo recognizable groups are distinguishable 
within Vireo on the basis of plumage (Hamilton 
1962): (1) species with eye-rings and wing-bars in 
(he subgenus Vireo. and (2) species with eye- 
stripes and lacking wing-bars in the subgenus 
Vireos viva. Johnson et al. (1988) recommended 
abandoning this dichotomy based on allo/yme 
evidence, but phylogenetic analysis using mito¬ 
chondrial DNA sequence data (Murray et al. 
1^94) supported recognition of the two subgenera. 
Department of Biology. Villanova University. 800 
Lancaster Avenue. Villanova, PA 19085, USA. 
L niversidad Autonoma Mctropolilnna-Xochimilco, Cal- 
zatia del Mucso 1100, Colnnia Villa Quictud. Delegaci6n 
Coyoacdn, CP 04960, D.F. Mexico. 
Instituio de Ecologta. A.C., Red dc Interacciones 
Multitrtificas, Apartado Postal 63. Xalapa, Veracruz 
91000, Mexico. 
'Current address: Department of Neurobiology and 
Behavior and Cornell Laboratory of Ornithology. Cornell 
University, Ithaca. NY 14853, USA. 
'Corresponding author; e-mail: jbl96@cornell.edu 
The -eye-ring' group includes eight little-studied 
species endemic to the West Indies or the adjacent 
Caribbean Coast of Mexico and Central America; 
one of the most range-restricted species among 
these is the Co/umcl Vireo ( V. hairdi). 
The Cozumel Vireo is endemic to Isla Cozu¬ 
mel, Quintana Ron, Mexico (Howell and Webb 
1995. AOU 1998). The species’ breeding biology 
is wholly unknown (Brewer and Orenstein 2010). 
Early records described the species as “very 
common” (Griscom 1926:11) and “more fre¬ 
quently encountered than any other species in 
woodland and secondary growth” (Bond 
1961:45). The Cozumel Vireo remains abundant 
(JBL, RLC, and JEMG. pers. obs.) despite the 
presence of feral cats (Felts cants) and dogs 
( Cam's familiaris) as well as other recently in¬ 
troduced potential predators, including a snake 
(Boa constrictor, present since the early 1970s; 
Martmez-Morales and Cuardn 1999, Romero- 
Najera et al. 2007) and black rats ( Ratttts rattus; 
Engstrom et al. 1989). Our objectives are to report 
the first descriptions of the Cozumel Vireo’s nest, 
eggs, and nesting phenology, and to compare our 
observations with available data for other ‘eye- 
ring’ vireos (if Hamilton 1962). 
METHODS 
Study Area.—We observed vireo nests during 
fieldwork (May-Jul 2009) on Cozumel focused on 
Black Catbird ( MelattoptUa glabrirostris ) breed¬ 
ing biology. Cozumel is in the Caribbean Sea, 
— 17.5 km off the Yucatan Peninsula’s coast, 
separated from the mainland by a deep channel: it 
has a land area of -490 knr (BirdLife Interna¬ 
tional 2012). Most of the island's vegetation is 
semi-deciduous or tropical deciduous forest with 
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