356 
THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 123. No. 2. June 2011 
TABLE 3. Frequency of search movements of warblers and vireos partitioned by different environmental and social 
factors at Gulf Coast stopover sites, 1994. 
Warblers Vireos 
Factor 
Hop 
Flutter 
Fly 
G 2 
p 
Hop 
Rutter 
Fly 
G’ 
f 
Site 
Grand Chenier 
Hackberry Ridge 
Smith Point 
Plot 
4,880 
11,079 
6,300 
216 
403 
205 
855 
1,243 
654 
117.38 
0.001 
541 
1,412 
792 
28 
64 
38 
137 
284 
150 
5.7 
0.226 
Control 
Disturbed 
Presence of vines 
10,654 
11,605 
333 
491 
1,359 
1,395 
20.96 
0.001 
1,420 
1,325 
69 
61 
297 
274 
0.1 
0.951 
No 
Yes 
Flocking 
14,665 
3,901 
587 
107 
1.746 
384 
22.97 
0.001 
1,589 
662 
82 
22 
369 
123 
6.8 
0.033 
In mixed flocks 
Solitary 
Migrant density 
9,147 
2,745 
405 
124 
1,151 
339 
0.13 
0.940 
632 
319 
28 
9 
182 
49 
14.7 
0.001 
High 
Low 
9,732 
12,527 
273 
551 
1,163 
1,589 
38.40 
0.001 
1,270 
1.475 
62 
68 
282 
289 
1.9 
0.389 
1984; Holmes and Recher 1986; Barrow 1990). 
The distance between potential perches is shorter 
in dense vegetation; consequently migrants hop 
more in areas with vine tangles than in areas 
without vines. Dense vegetation also decreases a 
bird’s scanning diameter, and makes it difficult 
for a bird to search for prey (Fitzpatrick 1981) 
Thus, hops are preferred to flights for a thorough 
search in areas with dense vegetation. 
Migrants tended to use more '“hops” in control 
plots and at Smith Point and Hackberry Ridge, but 
used more “flights” in disturbed plots and at 
Grand Chenier. These results are in accordance 
with the vegetation of our study plots as control 
plots were selected to have denser vegetation than 
disturbed plots. Vegetation was densest at Smith 
Point (Barrow et al. 2000: figure 5), whereas 
Hackberry Ridge had a much denser understory 
than Grand Chenier. The Grand Chenier site had 
the highest canopy and contained more mature 
trees than the other two sites. These results are 
also consistent with other studies. For example. 
Robinson and Holmes (1984) found that Ameri¬ 
can Redstarts and Red-eyed Vireos (Vireo oliva- 
ecus) took more flights in white ash (Fmxinus 
americana) than other tree species because white 
ash had lower vegetation density and more evenly 
distributed leaves than other trees. 
Social status such as foraging in mixed flocks 
and periods of high migrant density also affected 
search behavior. Both situations involved concen¬ 
tration of many individuals in a relatively restricted 
CoL^erSl^'l^lTexr ^ r"' 0 ""''" 1 * 1 S “ ial *r warbler, and v, re « a.« 
Flocking.^AII mteraetiorTtems^^^ftod'inodelsatfesignificant^p < o'ojg* = ^ = Density. V = Vine. andF = 
Factors in the model 
Site, Plot, Density 
Site, Plot, Density, Vine 
Site, Plot, Density, Flocking 
Site, Plot, Density, Vine, Flocking 
_Best fitted model 
Warblers 
(SPD) 
(SD, SV. PD, PV, DV) 
(SPD. PF) 
(SVF, SD, PF) 
(SP, SD, DV) 
(SD, PD) 
(DV. PF. S) 
