SHORT COMMUNICATIONS 
181 
TABLE 1. Clutch, brood, and fledgling parameters (mean ± SE. n) for parasitized (by Brown-headed Cowbirds) and 
non-parasitized Ovenbird nests in the Chippewa National Forest, Minnesota. 
Variable 
Parasitized 
Non-parasiUzcd 
V 
p 
dutch size 
3.0 ± 0.60 (6) 
4.8 ± 0.05 (99) 
-3.81 
<0.001 
Brood size 
2.8 ± 0.73 (5) 
4.5 ± 0.10 (71) 
-2.92 
0.003 
No. fledged 
2.5 ± 0.87 (4) 
4.4 ± 0.12 (55) 
-2.65 
0.008 
Days to >50 m J 
12.0(1) 
4.1 ± 0.71 (16) 
Days to >100 m b 
25.0(1) 
9.5 ± 1.14 (16) 
Adult care c 
3/9 (0.33) 
105/155 (0.68) 
1 Dm 10 irarel >50 m from nest. 
1 Days to travel >100 m from nest, 
Proportion of days adults were present during observations of fledglings during the cowbird supcractivc phase (Days 13-23). 
mixed northern hardwood-coniferous forests in the 
Chippewa National Forest. Itasca County. Minne¬ 
sota. USA (47 26' N. 93 40' W). We visited nests 
every 4 days to monitor condition and contents, and 
visited nests more frequently as the estimated 
fledge dale approached. We observed nests remote- 
0 wnh binoculars when possible and took different 
paths to and from nests to avoid developing trails 
leading to nesis. We recorded clutch or brood size 
and presence of cowbird eggs and nestlings during 
each observation. We weighed and banded Oven- 
ford nestlings with standard aluminum U.S. Geo¬ 
logical Survey leg bands 1 or 2 days before we 
expected nestlings to fledge. We attached radio 
transmitters to one (rarely 2-3) Ovenbird nestling in 
each nest, using a figure-eight harness (Rappole and 
Tipton 1991), Radio transmitters lasted —60 days, 
had a 0.5-1.0-km signal range during ground-based 
telemetry', and were 4.3-4.9% of nestling mass at 
hmeot attachment, decreasing to 3.0-3.5% as birds 
'cached maturity. We monitored fledglings daily 
and recorded location, activity, adult presence, and 
fledgling status (alive or dead). We recorded 
locations of nests and fledglings using handheld 
Global Positioning System units (100 points aver- 
aged per location) and derived distances from 
fledglings to the nest from which they Hedged using 
Geographic Information System software. We 
^corded parental activity as present or absent and 
note d if parents were feeding fledglings during each 
J S-20-min observation of the fledgling. Proportions 
01 observations when parents were present were 
h^sed on 95% confidence intervals. We visually 
inspected remains of dead fledglings for signs of 
predation and identified stomach contents when 
stomachs were recoverable. We compared clutch 
s Rc. hrood size, and number of Hedged young 
between parasitized and non-parasitized nests using 
Mann-Whitney U- tests. We report the number of 
days required for fledglings to travel >50 and 
>100 m from nests as means ± SE. 
RESULTS 
We monitored 115 Ovenbird nests during 2006- 
2008. six (5%) of which were parasitized by 
cowbirds (each with I cowbird egg). One parasitized 
nest was abandoned during the laying stage, one was 
depredated during the nestling stage, one fledged 
one Ovenbird with the cowbird egg unhutched, and 
three Hedged at least one Ovenbird and one cowbird. 
Parasitized nests contained smaller Ovenbird clutch¬ 
es (4/ = -3.8 \,P <0-001) and broods (£/= -2.92, 
P < 0.003), and Hedged fewer Ovenbird young (U 
= -2.65, P < 0.008) than non-parasitized nests 
(Table 1). 
Two of the three Ovenbird fledglings tracked 
from parasitized broods lost their transmitters 
within 2 days of leaving the nest and their fates 
were unknown. The third fledgling was in a brood 
with two other Ovenbirds and one cowbird. The 
mean mass of the three Ovenbirds when banded 
was 14.7 g. 1.2 g more than the mean mass of all 
Ovenbird nestlings weighed. The Hedgling with 
the transmitter weighed 15.5 g. 1.0 g more than 
the mean mass of all Ovenbird nestlings to which 
we attached transmitters. We monitored that 
Ovenbird Hedgling for 26 days, and 36 Ovenbird 
fledglings from 31 non-parasitized broods for 1 
to 49 days each. Twenty-six days after Hedging, 
the fledgling from the parasitized brood was 
dead, but there was no evidence of predation. Its 
stomach was empty. All stomachs recovered 
from fledglings of non-parasitized broods (n = 
4) contained multiple intact and partial insects 
(Coleoptera and Lepidoptera), and one also 
contained a snail (Pulmonata) and a seed. All 
fledglings recovered from non-parasitized nests 
had signs of predation. 
