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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 124. No. 2. June 20/2 
sensation from ‘eggs in the nest' may influence the 
completion of egg laying - in smaller nest boxes 
with potentially a smaller nest cup. any sense of a 
‘full nest' may he achieved with fewer eggs (i.e.. a 
smaller clutch size) than would be achieved in 
larger nest boxes. The impact of the smaller nest 
boxes is just a slight reduction in clutch size and 
little other effect on breeding biology. This effect is 
magnified when considering the entire season or 
life time production if individuals maintain the 
same nest box from year to year as is true for House 
Sparrows (Anderson 2006). 
There may be a nest-box size (or cavity size) 
too big to have any restrictive impact on size or 
bulk of any nest that may be built; below this size 
the nest box imposes physical limits on the size of 
the nest itself. It can be imagined the relationship 
between increasing cavity size with clutch size 
holds until cavity (or nest-box) size reaches (he 
point at which nest building has no constraints. 
Further investigation of House Sparrow nest box 
preferences would suggest looking at nest boxes 
encompassing a larger range in basal area or using 
nest boxes with a single entrance to two cavities 
of diflerent sizes. House Sparrows, being some¬ 
what colonial in their nesting biology, can be 
presented a situation offering a variety of nest-box 
types and sizes. Most nest boxes used by my 
Homewood colony were within I m of their 
nearest neighbor; individual pairs potentially have 
the full range of choice in selecting nest sites. This 
present examination has only looked at variation 
in basal area from 112 enr to 221 cm 2 and 
included no experimentation. 
Understanding preferences and nest box micro¬ 
climate is difficult to examine outside the labora¬ 
tory. Nest site selection involves more than just 
nest-box size; nest site preferences for House 
Sparrows in this colony setting would be influ¬ 
enced by interactions among all individuals in the 
colony, past breeding histories, and future available 
choices. The differences noted in clutch size 
among different nest-box sizes in experiments with 
European Starlings were explained by differences 
in the age composition of females using the 
different box sizes: young females were over¬ 
represented in the smaller boxes (Trillmich and 
Hudde 1984). First time breeders among House 
Sparrows have a smaller average clutch size and 
select nest sites later than older birds; however, 
once situated. House Sparrows show some site 
fidelity (Anderson 2006); all of these factors add 
complications for understanding. 
ACKNOWLEDGMENTS 
Over the years, a number of people have assisted in 
monitoring I louse Sparrows at this colony: Carvn. Gretchen. 
Gail, and Gloria Lowthcr; Monica and Judy Wilks: and Brian 
Wayne. I appreciated the generosity of neighbor Donald 
Callender (t) in allowing placement of four nest boxes on his 
garage just 1.9 m to the north of the main stud) sire. Editor 
Gait L. Braun, reviewer Douglas \\. Mock, and an anonymous 
reviewer were helpful in their criticism and guidance. 
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