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THE WILSON JOURNAL OF ORNITHOLOGY • Vol 124. No. 4. December 2012 
DISCUSSION 
Red-shouldered Hawk nestlings in southern Ohio 
appeared to he unharmed by infestations of Proto- 
cutliphora avium. We did not count the larvae found 
in ear canals, but we did not observe >10 in any 
nestling’s ear (ARW, unpubl. data). Infestations 
were apparently less intense than those reported by 
Tirrell (1978) and White (1963), in which larvae 
were found in multiple locations on the nestlings anti 
nestling mortality occurred. The reproductive rate (in 
terms ot young fledged per nest) did not differ 
between infested and non-infested nests at HH and 
did not differ from the reproductive rate at SWOH. 
Sixty percent of Red-shouldered Hawk nests at 
HH in south-central Ohio contained the blow fly 
P. avium, but nests in SWOH. -180 km west, 
were entirely free of this ectoparasite. This 
difference was not an artifact of the study sample 
size, as we have not observed P. avium at SWOH 
and we have consistently found -50% of nests 
parasitized at HH in out 15-year study of Red¬ 
shouldered Hawks nesting in both study areas 
(CRD and JLH. unpubl. data). 
One possible explanation for the presence of P 
avium at HH but no. SWOH is that the suburban 
landscape is somehow unsuitable for P. avium It 
is not uncommon for Protocol liphora to be absent 
from some areas, particularly where the host 
population is relatively recently established or the 
environment is unstable (T. L. Whitworth, pen. 
comm.). Some parasite species are less abundant 
in urban areas (Marcogliese 2005) and some 
researchers suggest parasite communities may be 
appropriate indicators of environmental health 
(Lafferty 1997; Marcogliese 2004. 2005) How¬ 
ever. urbanization may affect parasite populations 
and communities in diverse ways. Urban song- 
birds had fewer Protocol liphora (>. sialia: Moore 
). fewer ticks (Ixodes; Gregoire et al. 2002 
Evans et al 2009, and fewer blood parasites' 
(Fok ' d ' s e ' 2°08). Prevalence of one Dipteran 
ectoparasite (Phil,,mi, /u.ru-ri, on Northern 
Mockingbirds polygbnos) was not di- 
et C I y ?om P° Urbanization in Rorida <Lc tiros 
et at. 2011 ). Ectoparasites, including Pmocalli- 
exaZ,e PP i„ n F y i ak ; > 7^' “ Polluticn: for 
example, F ln | an d, P. aiurea larva( . werc , 
complex r te “i" 0 * T" inss closer >° •' ^lory 
complex releasing sulfuric oxides and heavy 
metals into the atmosphere fEeva el al 19941 X 
Another possible explanation for ,he absence of 
p. avmm at the SWOH study area is that it may be 
outside of P. avium’s distributional range, while 
HH is within it. The genus Protocalliphora is 
considered ’predominantly northern* (Sabroskv 
et al. 1989) or ‘mainly boreal' (Bennett and Whit¬ 
worth 1991 ) and the range of P. avium extends from 
Alaska and Yukon Territory to Quebec and 
( onnecticut and south to Pennsylvania and Nebraska 
(Sabrosky et al. 1989). Reports of this species within 
the United Slates are from New York (Sargent 1938. 
Crocoll and Parker 1981). Minnesota (Bohm 1978). 
Wisconsin (King et al. 2010). Michigan (Hamer- 
strom and Hamerstrom 1954). and as far south as 
Pennsylvania, northern Iowa, and northern Illinois 
(Sabrosky et al. 1989). Our report of P. avium in 
south-central Ohio is apparently the southernmost 
report ol this species to date. However, published 
reports on the presence of (his species are scattered 
and mostly anecdotal and may not represent the full 
distribution range. 1 locking Hills, particularly the 
western pan ol our study area, includes gorges 
containing northern microclimates and habitats, and 
is connected by a corridor of semi-wooded habitat to 
northeastern Ohio and western Pennsylvania. SWOH 
is in the Interior Plateau ecorcgion and is bordered on 
the north by Hat. primarily agricultural lands with 
lew forests. Thus, it is possible SWOH is effectively 
isolated from northern species. Red-shouldered 
Hawks are not present or have an extremely limited 
distribution in the counties north of SWOH. although 
other hosts of P. avium. Red-tailed Hawks. Cooper's 
Hawks, and Great Homed Owls (Bubo Virginians), 
are present in those regions (Pcteijohn 2001). 
Il HH in south-central Ohio is at the edge of 
the lange ol P. avium . we might expect lighter 
infestations and/or a lower proportion of nests 
in ested. compared to more northern regions. We 
lound 60% of nests infested with P. avium but. 
in northern Wisconsin, 91% of Red-shouldered 
Hawk nests were infested (King et al. 2010), and 
m cent ral New York, nearly 100% of nests of both 
e -tailed and Red-shouldered hawks were in¬ 
fested (Sargent 1938). We note it is possible that 
we underestimated the prevalence of P. avium, as 
we did not examine the nesting material at all 
nests, and we did not examine areas of the 
nestlings other than the ears; had we done so. we 
may have found more nests infested. 
We do not know the reason for the difference in 
i ow fly abundance between our two study sites, 
and hope this paper will encourage researchers to 
examine the distribution of ectoparasites such as P. 
tn """ anc * , * le ' r relationships to their raptor hosts 
and to the environment. Additional information on 
