Hallworth et al. • LOUISIANA WATERTHRUSH HABITAT USE 
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TABLE 2. Values (x ± SE) measured in 3-m radius plots for mud, leaf litter, water, and vegetation at Louisiana 
Waterthnish foraging and random non-use locations presented as percent ground cover in the Caribbean National Forest, 
Puerto Rico. 
Mud Leaf litter Water Vegetation Canopy Prey 
Use 38.8 ± 4.89 43.5 ± 4.12 11.7 ± 2.69 47.9 ± 3.60 87.0 ± 3.11 8.04 ± 0.73 
Non-use 1.04 ± 0.58 91.7 ± 1.99 3.13 ± 2.92 48.1 ± 5.07 94.7 ± 0.35 5.26 ± 1.24 
ages of time along streams than SYs but older 
birds did use streams more than expected based 
upon availability whereas younger birds spent 
more time along roads and within housing 
developments than expected. These results sug¬ 
gest older birds assert dominance over younger 
individuals and secure the highest quality habitat. 
Conspecific aggression was observed when two 
individuals crossed paths, and these encounters 
were only observed along streams (MTH, pers. 
obs.). Waterthrush, like Ovenbirds (Seuirus aur- 
ocapilla), may maintain and defend smaller 
territories ihrough active defense of core areas 
and during chance encounters with conspccifics 
(Brown and Sherry 2008). ASYs had significantly 
smaller home ranges than SYs also suggesting 
older individuals are able to secure higher quality 
Mud Non use Stream 
Location 
HG- 2. Prey availability (log transformed to meet the 
assumptions of normality) was significantly greater in 
locations used (mud and stream) by Louisiana Waterthrush 
•ban randomly selected non-use locations within their home 
f ange (Non use). The box depicts the median (solid line in 
the box), lower and upper 25% tjuartiles, and whiskers 
represent the data range. 
home ranges (Holmes et al. 1996); however, 
neither home range nor core area size was 
correlated with prey availability. Roost sites 
(Smith et al. 2(X)8) and cover (Watts 1991) may 
also influence home range size. 
Waterthrush mostly foraged along streams but 
also used off-stream habitats with appropriate 
ground substrate, especially in areas with concen¬ 
trated arthropod abundance. The most important 
ground feature in off-stream areas used for foraging 
was the amount of muddy substrate. Foraging 
locations had nearly 40% muddy ground cover 
compared to 1% in non-use areas. Northern 
Waterthrush (Parkesici nvveboracensis) and 
Louisiana Waterthrush seek saturated soils that 
are often rich in arthropods (Smith et al. 2010). 
Foraging locations had less than half the leaf litter 
compared to non-use areas. There was nearly four 
times greater standing water and greater prey 
abundances in areas used for foraging. Waterthrush 
are ground foragers and attracted to moist sub¬ 
strates. Thus, when not along streams they seek 
areas where ground arthropods are in higher 
concentrations. Prey availability was the most 
parsimonious model that influenced habitat use, 
followed by a model containing prey availability 
and percent leaf litler, The importance of leaf litter 
is likely due to waterthrush actively searching for 
arthropods by flipping leaves as they forage both 
on and off stream (MTH. LRR. pers. obs.). 
Individual body condition was negatively corre¬ 
lated with amount of time foraging along the 
stream which may be influenced by the amount of 
conspecific encounters and time spent defending 
core areas. Conspecific encounters and aggression 
were only observed along streams (MTH, LRR. 
pers. obs.). The riparian habitat in this study area 
has been affected by development which may have 
impacted water quality and stream invertebrate 
richness and ahundance. The streams still attract 
waterthrush. but they may not have suitable 
conditions for invertebrate productivity. 
Return rates (13-29%) in our study were low 
for a neotropical migrant when compared to 
