The Wilson Journal of Ornithology 123(2): 347-3 59, 2011 
SEARCH BEHAVIOR OF ARBOREAL INSECTIVOROUS MIGRANTS 
AT GULF COAST STOPOVER SITES IN SPRING 
CHAO-CHIEH CHEN, 1 ’ WYLIE C. BARROW JR., 25 
KEITH OUCHLEY, 14 AND ROBERT B. HAMILTON 1 
ABSTRACT.—Search behavior of arboreal insectivorous migrants was studied at three stopover sites along the northern 
coast of the Gulf ofMexico during spring migrations, 1993-1995. We examined it search behavior was affected by phylogeny, 
or by environmental factors. A sequence of search movements (hop. flutter, or flight) in a foraging bout was recorded for each 
migrant encountered. Search rate, frequency, and distance of movements were calculated for each species. Search rate was 
positively correlated with proportion of hop. but negatively correlated to flight distance. Hop distance was positively correlated 
to tarsus length, as was flight distance to wing length for the 31 species of migrants. Cluster analysis indicated closely related 
species generally have similar foraging modes, which range from "sit-unil-waif' of flycatchers to "widely foraging of 
warblers. Migrants tended to use more hops in dense vegetation, but more flights in areas with sparse vegetation. Migrants also 
used more flights when foraging in mixed-species flocks and during periods of high migrant density. Logistic models indicated 
warblers were more influenced by environmental factors than vireos. possibly because warblers are near-perch searchers and 
more affected by these factors, Received 6 May 2010. Accepted 17 December 2010. 
Numerous studies have reported on the search 
behavior of forest birds (Williamson 1971; 
Morton 1980; Fitzpatrick 1981; Robinson and 
Holmes 1982, 1984; Holmes and Recher 1986; 
Hutto 1988; Lovette and Holmes 1995), and some 
have found that environmental factors affect 
search behavior of birds. Robinson and Holmes 
11982. 1984) in New Hampshire, and Holmes and 
Recher (1986) in Australia, found that search 
lactics of insectivorous birds were related to 
vegetation structure and prey availability. Prey 
type and distribution and abundance of prey can 
Jlso affect search behavior of birds (Davies 1977, 
Griffiths 1980. Graber and Graber 1983, Holmes 
and Schultz 1988, Lovette and Holmes 1995). 
Fitzpatrick (1981) concluded that visual field 
complexity and prey dispersion characteristics are 
the two most important factors affecting search 
strategies of tyrant flycatchers. 
Many Nearctic-Neotropic migrant species, such 
as wood-warblers (Parulidae), vireos (Vireoni- 
dae), and flycatchers (Tyrannidae). have declined 
dramatically in the past few decades (Hall 1984; 
School of Renewable Naiural Resources, Louisiana 
Siaie University, Baton Rouge. LA 70803, USA. 
L.S. Geological Survey. National Wetlands Research 
f-enter. 700 Cajundomc Boulevard. Lafayette, LA 70506. 
USA. 
Department of Biomedical Science and Environmental 
Biology, Kaohsiung Medical University. 100 Shih-Chuan 
Road. Kaohsiung 807. Taiwan. 
‘Current address: The Nature Conservancy, P. O. Box 
925, Baton Rouge, LA 70821, USA. 
‘Corresponding author; e-mail: barroww@usgs.gov 
Terborgh 1989. 1992; Peterjohn et al, 1995; 
Holmes and Sherry 2001; Ballard el al. 2003). 
Most of these studies have been conducted in 
breeding (Lynch and Whigham 1984. Wilcove 
1985. Robinson 1992. Holmes and Sherry 2001), 
or wintering areas (Lovejoy 1983, Rappole and 
Morton 1985, Rappole 1995), and relatively fewer 
studies have been conducted at stopover sites 
(Moore el al. 1990, 1995; Rodewald and Britting- 
ham 2002; Buleret al. 2007). Moore (2000) noted 
the migratory pattern is an important part of the 
annual cycle, and it is crucial to put more efforts 
into understanding stopover ecology to complete 
our knowledge of the Nearctic-Neotropic migra¬ 
tion system. 
Stopover sites are critical in providing food 
resources for migrants (Berthold and Terrill 1991, 
Wang and Moore 1997, Moore 2000). En route 
migrants are in higher demand of energy at 
stopover sites compared to breeding areas (Bie- 
bach 1996), especially prior to taking off after 
finishing a long non-stop flight. Most en route 
migrants search for food intensively and contin¬ 
uously at staging areas (Moore and Wang 1991, 
this study). We investigated search behavior of 
arboreal insectivorous migrants at three stopover 
sites (6 plots) along the northern coast of the Gulf 
of Mexico in spring. 1993-1995. These stopover 
sites are within the Chenier Plain, and three of the 
plots were managed for cattle grazing (Barrow et 
al. 2000). Our objectives were to examine if 
search behavior of migrants was affected by: (1) 
environmental factors (e.g., vegetation structure), 
(2) social status (flock, high density), or (3) 
phylogeny. 
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