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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 123, No. 1, March 2011 
(e.g., Laurance et al. 2004, Gillies and St. Clair February to April, and a less pronounced dr}' 
2008, Lees and Peres 2009), but it is not clear if season from September to October (Sanford et al, 
this has direct or immediate impacts on the 1994). 
persistence of populations in fragments, because The natural history of the Chestnut-backed 
populations can, in theory, persist for some time Antbird is summarized by Woltmann etal. (2010). 
in the absence of immigration (Moore et al. 2008). 
Compared to estimates of apparent survival, 
few studies exist on natural movements of 
an thirds, and understory insectivores in general. 
Nearly all studies of antbird movements have 
focused on breeding (as opposed to natal) 
dispersal (sensu Greenwood and Harvey 1982), 
because marking and following sufficient num¬ 
bers of nestlings is logistically difficult in forest 
species with cryptic nests, long breeding seasons, 
and low nest success rates. Breeding dispersal has 
often been quantified in terms of territory¬ 
switching, because most species defend territories 
year-round. Previous studies of antbirds show: (1) 
annual survival of antbirds is typically relatively 
high compared to similar-sized temperate birds 
(Blake and Loiselle 2008), (2) movements by 
territorial individuals may occur regularly, but on 
a small scale (within a few territory-widths; 
Greenberg and Gradwohl 1997, Morton et al. 
2000, Fedy and Stutchbury 2004), and (3) territory 
locations and boundaries within non ant-following 
species are fairly constant over time (Greenberg 
and Gradwohl 1986, Morton et al. 2000). 
We studied a population of Chestnut-backed 
Antbirds (Myrmeciza exsul ) in northern Costa 
Rica from 2004 to 2009 to estimate survival rates 
and to characterize breeding dispersal. Our 
objectives were to: (1) generate estimates of 
apparent annual survival and detection probabil¬ 
ity, and (2) quantify between-year turnover and 
territory switching behavior within a large forest 
preserve. 
METHODS 
Study Area .—We conducted this study in the 
Caribbean lowlands of northern Costa Rica, which 
were essentially completely forested prior to 1950 
(Joyce 2006), but have become increasingly 
fragmented, largely by agricultural land uses. 
The La Selva Biological Reserve (hereafter “La 
Selva ) is a largely forested lowland preserve 
(35-137 m asl; McDade and Hartshorn 1994) in 
Heredia Province, encompassing >1,100 ha of 
old-growth tropical wet forest. La Selva is 
currently surrounded on three sides by a largely 
agricultural matrix. Annual rainfall is nearly 
4,000 mm with a predictable dry season from 
Individuals are paired and maintain territones 
year-round, and are highly sedentary, at least at 
short (<1 year) time scales (Marcotullio and Gill 
1985, Stutchbury et al. 2005, Losada-Prado 2009). 
Moore et al. (2008) provided evidence of poor 
dispersal by this species by demonstrating its 
inability to sustain flight for 100 m over water, 
although how this limitation applies to dispersal in 
more typical terrestrial settings is unknown. 
Field Procedures .—We selected a 300-ha focal 
study area (200 ha from 2004 to 2005; 300 ha 
from 2006 to 2009) dominated by old-growth 
forest (two territories included in survival analy¬ 
ses were outside the focal plot, but in similar 
habitat). Forty of 41 territories monitored were in 
forest at least 40 years of age with a well 
developed canopy and understory; the other 
territory was in older second-growth with a 
canopy height of ~3 m. Birds were lured into 
mist nets using conspecific playback, uniquely 
banded with a numbered aluminum band and 
three colored plastic leg bands, and released. Bird 
capture and marking began in December 2004, 
and annual dry-season surveys were conducted 
February-March 2005-2009 (and into Apr 2009). 
Chestnut-backed Antbirds in post-juvenal 
plumages are readily identified as male or female 
based on underpart coloration (Wolfe et al. 2009). 
Incomplete knowledge of the timing of definitive 
prebasic molt and observations of breeding 
activity nearly year-round at La Selva indicate 
that Hatch-Year (HY) and After-Hatch-Year 
(AHY) terminology is inappropriate at this site. 
We classified birds as “adult” (fully ossified 
skull and definitive plumage) or “juvenile” (skull 
<90% ossified or formative plumage; Howell et 
al. 2003), and note we occasionally captured 
“juvenile” birds in breeding condition (cloacal 
protuberance and/or brood patch). 
We attempted to relocate all previously marked 
birds during each annual survey, and to capture 
any unbanded individuals. Territories were thor¬ 
oughly searched during morning hours with good 
weather (when birds are most active and vocal), 
and vocalization playback was used to find and 
identify individuals. We considered a territory 
unoccupied if no bird was found after two 
separate searches (minimum 45 min each) at least 
