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THE WILSON JOURNAL OF ORNITHOLOGY . Vol. 123, No. 3, September 2011 
TABLE I. 
Number of Red-eyed Vireos banded between 26 June and 15 August 2007 in the Ganaraska Forest. Ontario. 
Gender 
Hatching year 
After hatching year 
Second year 
After second year 
Totals 
Unknown 
25 
0 
3 
4 
32 
Female 
0 
0 
13 
24 
37 
Male 
0 
1 
11 
28 
40 
Totals 
25 
1 
27 
56 
109 
(>2 km) dispersal distances compared to the other 
nine re-encounters (<350 m). 
DISCUSSION 
Our re-encounter rate of adult Red-eyed Vireos 
was low for a forest passerine, but the re¬ 
encounter rate (12%) for hatching year birds 
appeared high compared to the average of other 
studies (3.7%, SE = 0.6, n — 51 studies; 
Weatherhead and Forbes 1994). It is difficult to 
make inferences from our small sample size, but 
the small samples may highlight potential bias in 
survival estimates as a result of interannual 
dispersal. Most studies or marked Red-eyed 
Vireos have been spatially limited (e.g.. one 64- 
ha study plot: Savidge and Davis 1974; nine 30-ha 
study plots: Marshall et al. 2002). Our survey 
included samples from across 4,600 ha and we re¬ 
encountered three Red-eyed Vireos that dispersed 
farther than the longest previously reported 
distance (545 m; Marshall et al. 2002). Most 
Red-eyed Vireos we re-encountered (9 of 12, 
75%) moved >100 m, suggesting dispersal from 
the previous year’s territory {sensit Marshall et al. 
2002). Thus, apparent survivorship estimates may 
be biased by reduced detection probabilities 
because of dispersal both within the study area 
and potential emigration from the study area. 
Methodological issues biasing detection prob¬ 
ability could have affected our re-encounter rates. 
We only re-encountered a few banded individuals 
using playbacks in the same location in the 
subsequent year, despite our success using mixed 
species alarm calls to attract vireos during initial 
capture. The low re-encounter rate is due to 
failure to attract all banded birds to the playback, 
brief responses to the playback, and to the 
generally long dispersal distances of returning 
birds. For example, we were able to attract two 
banded males with active nests <170 m from lire 
playback, but we did not attract a third male also 
with an active nest within 70 m. Another 
individual responded to the playback but not 
sufficiently long to read the color markings. We 
re-encounlcred most birds beyond the maximum 
distance that birds appeared to respond to the 
playback (>170 m) which suggests a systematic 
search of larger areas around all banding locations 
would have probably increased our re-encounter 
rate. There is some concern that searching large 
areas may be inefficient (Cox and Jones 2010) or 
that models accounting for dispersal may over¬ 
estimate apparent survivorship (Cooper et al. 
2008). but long-distance adult and natal dispersal 
of Red-eyed Vireos must be recognized in future 
investigations. 
TABLE 2. Interannual dispersal distances (m) of Red-eyed Vireos in the Ganaraska Forest. Ontario. Age at banding 
is shown. 
Male 
Mean ± SD 
Median* 
9.870' 
70" 
4.970 ± 6,930 
4,090 
„ M ? ,es observed on territory but no nest found in 2008. 
^ Distance measured to nest. 
Median for age group irrespective of gender. 
350" 
200 " 
250" 
170" 
2,040' 
350" 
40° 
50" 
220 ” 
540 ± 848 
220 
