The Wilson Journal of Ornithology 123 ( 3 ): 567 - 574 , 2011 
HABITAT USE OF THE LOUISIANA WATERTHRUSH DURING THE 
NON-BREEDING SEASON IN PUERTO RICO 
MICHAEL T. HALLWORTH, 1 ’' LEONARD R. RE1TSMA, 1 AND KYLE PARENT 1 
ABSTRACT.—We used radiotelemetry to quantify habitat and spatial use patterns of neighboring Louisiana 
Waterthrash [Parkesia motadlla) along two streams in the Caribbean National bores, m Puerto Rtco dunng )05-20()7^ 
Home range sizes varied with younger birds having larger home ranges and core areas than older Turds A btrds occupied 
me length of stream but a wide range of off-stream habitats were also used. Oll-stream habitats mcludelarange o 
disturbance from residential areas to small saturated pastures. Neighbors exhibited a w,de range of overlap n.home^ranges 
(x - 20%, and older birds had more overlap than younger birds. The greatest percent 
(64.4%, followed by muddy substrate (26.5%). housing developments (7.4%). and roads (1.7%). The gee P P a 
:mie foraging along streams indicates this is the preferred habitat tor this species, sc o o , 2 010. 
strategy of exploiting food-rich ground substrates, and in particular those with high moisture, ete i 
Accepted 5 February 2011. 
Identifying mechanisms that limit and regulate 
populations is critical in understanding population 
dynamics. Identifying these mechanisms for 
migratory animals is difficult because of the large 
and often separate geographic areas in which they 
occur annually (Marra and Holmes 2001). Multi¬ 
ple processes can operate at different times in the 
annual cycle and in geographically distinct 
locations. These processes can influence factors 
that affect population growth rate (i.e.. survival 
and reproduction) including inter- and intra- 
specific competition, and predation. Most studies 
of long-distance migratory birds have focused on 
population regulating mechanisms during the 
breeding season. 
The primary resource requirements for migra¬ 
tory birds during the non-breeding season are food 
and shelter from predators (Brown and Sherry 
2008). Food availability (Sherry and Holmes 
'9%. Sherry et al. 2005). dominance-mediated 
habitat segregation (Wunderle 1992, Parrish and 
Sherry 1994, Marra and Holmes 2001). predator 
pressure (Watts 1991). and proximity to breeding 
areas iCristol et al. 1999, Jenkins and Crislol 
^002) affect the distribution of many neotropical 
migrants during the non-breeding season. 
Habitat occupancy during the non-breeding 
reason is an important component of the annual 
c ycle for neotropical migratory birds (Marra el al. 
1098); however, empirical data on habitat occu- 
' 7 PI»th State University. 17 High Street, Plymouth. 
N H 03264, USA. 
Current address: Smithsonian Institution's Migratory 
Bird Center. National Zoological Park. Washington, D C.. 
20008, USA. 
3 Corresponding author; e-mail: mhallwor@gmu.edu 
pancy and use during the non-breeding season are 
lacking for most neotropical migrants. Non¬ 
breeding occupancy has been shown to affect 
annual survival (Marra and Holmes 2001), spring 
migration departure dates, arrival in breeding 
areas, number of young produced (Reudink et al. 
2009), and natal dispersal (Studds el al. 2008). 
~ Neotropical migrants use multiple behavioral 
strategies including territoriality (Holmes and 
Sherry 1992, Marra et al. 1993). floating (Brown 
and Sherry 2008). and joining mixed species 
flocks (Ewert and Askins 1991, Latta and 
Wunderle 1996, Gram 1998, Jones et al. 2000, 
Warkentin and Morton 2000, Potnara et.al. 2007) 
during the non-breeding season. These behavioral 
strategics may be influenced by gender, food 
availability (Brown and Sherry 2006), and/or 
intra-and inter-specific competition which may 
affect body condition and annual survival. 
The Louisiana Waterthrash (. Parkesia motei- 
cilla). hereafter waterthrash. is a large (19.6 ± 
1.4 g) (Mattsson et al. 2009), monochromatic 
neotropical migratory warbler that breeds along 
first to third order perennial streams in deciduous 
and evergreen closed-canopy forests Jit medium to 
high gradients. They breed in the eastern United 
States from Wisconsin to central New England in 
the north to eastern Texas and northern Florida in 
the south. They overwinter throughout the Carib¬ 
bean and Central America (Mattsson et al. 2009) 
Waterthrash have been used as indicators of 
stream integrity (O'Connell et al. 2003). Densities 
of breeding individuals are reduced along fresh¬ 
water streams with macroinvertebrate communi¬ 
ties compromised by stream acidification and 
anthropogenic land use changes (Mattsson and 
567 
