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THE WILSON JOURNAL OF ORNITHOLOGY • Vo/. 124. No. 4. December 20/2 
DISCUSSION 
Nighthawk nestlings moved greater distances 
between daily use-sites as nestlings increased in 
age. Chicks ol 1—5 days ol age moved no more than 
4 m a day from their previous use-site. However, 
nighthawk nestlings regularly relocated greater 
distances after day 5 between daily use-sites, 
although short-range movements (- 5 m) were 
recorded throughout the nestling period (Table I) 
Common Nighthawk feet and legs are poorly 
adapted for ambulation and these physical limita¬ 
tions may explain the reduced range of movement 
observed during the early nestling stage. However 
that short movements (- 5 m) occurred even for 
young >11 days of age suggests there are likely 
other factors influencing nestling movement. We 
recognize that by regularly visiting the use-sites and 
handling young we initiated disturbance that could 
have influenced nestling movements. However ill 
nest visits were conducted similarly and there was 
still a clear movement distance pattern with respect 
to nestling age. Our limited observations („ = ^ t)( - 
nestling movements following severe disturbances 
(partial predation, and a serious injury likely due to 
attempted predation) suggest there may be a 
relationship between the severity of disturbance 
and the distance nestlings move. Common Night- 
hawks may be able to differentiate between more 
severe disturbance events and lesser ones, although 
our protocol did not allow us to test this hypothesis 
Which microhabitat features are important for 
nest and use-site selection and inter-use-site 
movement routes remains unclear as are the 
spec,tie cues that elicit nestling movements We 
were unable to discern any aural or visual cue that 
prompted the nestlings to follow the female parent 
trom the nest based on our video footage of a use- 
site relocation. However, nestlings began to stir 
and commence movement after the female parent 
stopped brooding and began walking away from 
the nestlings, suggesting that adults may be 
responsible for use-site selection at least while 
the nestlings are young (s 5 d) 
The growth rate of nestling nighthawks is 
comparable to reports for other young nightjars 
such as Australian Owlet-nightjars {Aegothl/es 
ensunus) (Brigham and Geiser 1997, and Com¬ 
mon I °orw,Ms (Pha/aenopti/us rwtiullii) fCsada 
and Brigham 1994). Similarities in nes, predating 
pressure and life history strategies have been 
invoked to explain similarities in growth rates of 
songbird species (Remes 2006, and may explain 
the general likeness between the growth rates of 
these nightjars. Common Nighthawk nestlings 
overcame asymmetrical masses associated with 
asynchronous hatching within several days of 
hatching unlike Common Poorwill nestlings, 
which are reported to take up to 14 days to reach 
equivalent masses (Csada and Brigham 1994), We 
did not observe feeding behaviors of Common 
Nighthawk nestlings or adults and are unable to 
comment on the potential role of food availability 
and quality. However, selection may favor parents 
with two equally developed nestlings that are able 
to relocate similar distances. 
Understanding the nature of nestling relocation 
lias important implications for future survey 
efforts, evaluation ol reproductive success, and 
population analyses. Common Nighthawk nests 
aie difficult to find and often just as difficult to 
relocate. Having a general guideline for night- 
hawk nestlings' movement potential will allow for 
more certainty in identifying nest fates in future 
studies. Daily nest survival rates and fecundity 
estimates would also be improved. Our nestling 
growth rate curve will provide a basis for 
comparison across other ecological contexts, 
Developing a better understanding of diverse 
nestling behaviors in birds and other taxa enriches 
om understanding of natural histories and important 
selective pressures shaping life history strategies. 
ACKNOWLEDGMENTS 
Wc express our deep gratitude to members of (he 
hanoun Laboratory for support at all stages of this 
project. Funding for GRK during summer 2010 was 
provided by a National Park Service Grant lo ADC. GRK 
thanks the University of Wyoming Honors Prosratn for 
providing a generous scholarship during this study. We 
' un . ' * Braun, R. M. Brigham, C. P. Woods, and C. 
' .iiiiriL/ Del Rio lor providing helpful comments on an 
s.n u i \ vision ot this manuscript. Our study was performed 
'"is 11 the auspices ot the University of Wyoming's 
nstinuional Animal Care and Use protocol * A-32164N 
. S 111,1 V ' <Jco '4 die nestling movement event is posted at 
p://\vvvw.youtube .comAvatch'?v=JR_z I v86Kr4. 
literature cited 
Brigham. r M. and F Geiser. 1997. Breeding biology of 
ustialian Owlet-nightjars Aegolheles eristam in 
euculypt woodland. Emu 97:316-321. 
Brigham, r. m. j anet Ng r g Pollin and s . d . 
RlNDAL. 2011, Common Nighthawk (ChordeHes 
minor). The birds of North America. Number 213. 
GOLI US; N ' E - E- C. Coixias. 1984. Nest building and 
binl behavior. Princeton University Press. Princeton. 
New Jersey, USA. 
