384 
THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 124. No. 2. June 2012 
during 4 years. Financial support was provided by the 
Katherine Ordway Foundation and the Dexter Fellowships 
in Tropical Conservation Biology. Alexander Skutch 
Award (Association of Field Ornithologists). Louis Agassiz 
Fuertes Award (Wilson Ornithological Society), and 
Alexander Wetrnore Award (American Ornithologists’ 
Union). Wc thank SERNAP for allowing us to work in 
the buffer area of Manu National Park. 
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The Wilson Journal of Ornithology !24(2):384-389, 2012 
Does Nest-box Size Impact Clutch Size of House Sparrows? 
Peter E. Lowther 1 
ABSTRACT.—I monitored the breeding biology of 
House Sparrows (Passer domesticus) in a suburban 
colony in Cook County, Illinois, USA. I found a 
significant statistical correlation between dutch size 
and the base area of the nest box (r 0.592, P < 
0.0029) with mean clutch size varying from 4.49 eges 
(in a 'small' nest box, 112 cm* basal area) to 4.77 eggs 
(in a ’large’ nest box, 221 cm* basal area). Other 
measures ol breeding success (hatching and Hedging 
success, mean egg mass, and nestling condition) had no 
statistically significant relationship with nest-box size. 
Measures ol nest site preferences, as suggested by 
earlier date of first egg of season or by greater number 
of broods per season, also show no statistically 
significant correlation with nest-box size. Received 28 
September 2011. Accepted 12 December 2011. 
The ‘natural’ non-cavity nest of House Sparrows 
(Passer domesticus) is u globular structure placed in 
IL USeUm ■ | ,40 ° SUU "’ Lake Shore D "ve. Chic 
il 60605. L.SA; e-mail: plowther@fieldmuseum.org 
trees, —20-25 cm diameter and 15-20 cm height: 
however. House Sparrows have a close association 
with human-impacted habitats and will make use of 
nooks, crannies, and other cavity-like sites within 
which to build nests, and readily use nest boxes 
(Anderson 2t)06). Nest boxes are convenieni for 
investigators to monitor the breeding biology of 
birds. They also provide a nest site environment tlial 
can be easily quantified or that can allow 
experimentation (Lambrechts et al. 2010). 
Experiments and field studies of several cavity- 
nesting species have found that clutch size varies 
with size of the cavity or nest box (e.g.. Lhhrl 
1973, Gustafsson and' Nilsson 1985), but this 
relationship has not been found to be true for all 
species lor which this has been investigated (e.g . 
Karlsson and Nilsson 1977, Purcell et al. 1997). 
There is no clear understanding of actual causes 
that can explain this relationship. 
I monitored the breeding biology of a small, 
suburban nest-box colony of House Sparrow' 
