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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 123, No. 2, June 2011 
are F b?ack cirHef ^ Vegem ™ surve y s with ^ ^as denoting forested areas. Active nests of Mariana Crows 
are black circles and random sites are black triangles. 
We performed a discriminant function analysis 
(DFA) which allowed us to statistically control for 
numerous intercorrelated vegetative (stem and 
DBH) variables. All variables were included 
initially, and then reduced in an iterative process 
to identify the smallest set of predictor variables 
which maximized predictive power. Jack-knifed 
classification percentages were reported in all 
cases. Some variables required log transformation 
o meet the assumption of normality. One variable 
(distance to a building) could not be compared for 
active nests and random plots because it was not 
measured unless a building was within 300 nr no 
she V S Wi , thi " 300 1,1 0t ' acli «= nest 
site. Variables eliminated from the DFA of 
successful versus unsuccessful nests due to 
€ s si ‘“ and number of nMS ° f 
insufficient sample size caused by some missing 
data were: slope, elevation, distance to road, and 
distance to edge. Mean stem counts and mean 
DBH values for each species were calculaied for 
each sample. The average stem counts and DBH 
values for each species were then summed across 
species to form two novel variables: total number 
of stems per plot and sum of the mean DBH 
These variables represented forest density and 
maturity, respectively. The genus Eugenia in¬ 
cludes two species on Rota that are difficult to 
discriminate and. for the purposes of these 
analyses, we use the genus to collectively refer 
to these two species. However. E. thompsonii was 
easy to discriminate and was noted separately 
Dichotomous and categorical variables were 
analyzed with contingency table tests. The Yates 
correction was performed when expected cell 
values were <5 (Sokal and Rohlf 1981). 
Study site 
Duge (DU) 
Golf Course (GC) 
Lalayak (LA) 
Mochong (MO) 
Palii (PA) 
Rail Release (RR) 
Totals 
Number of nests 
6 
6 
10 
12 
9 
12 
55 
Number of i 
10 
10 
10 
10 
10 
10 
60 
sites 
RESULTS 
Descriptive Characteristics of Nest Sites.-- 
species used by Mariana Crows for nesting on 
Rota included A'abang (Eugenia reinwardtiaflO ). 
Fagot (Neisospemta oppositifolia). Ifit {Itiisia 
bijuga), and Zebra wood (Guettarda speciosa) 
and were chosen significantly more often than 
16 other species of nest trees (x* = 82.94. df = 
P < - 0.001; Table 2). The mean height of the 
