The Wilson Journal of Ornithology 123 ( 3 ): 515 — 520 , 2011 
PROVISIONING BEHAVIOR OF MALE AND FEMALE 
GRASSHOPPER SPARROWS 
JENNIFER ADLER 1 AND GARY RITCHISON 12 
ABSTRACT.—We examined the provisioning behavior of male and female Grasshopper Sparrows (Ammodramus 
5 avannarum) during 2002 and 2003 by videotaping nests (n = 15) and subsequently reviewing tapes to quantify 
provisioning rates and identify prey items. There was no difference in provisioning rates of male and female Grasshopper 
Sparrows (P = 0.13) with mean rates of 2.16 visits/hr for females und 1.86 visits/hr for males. Provisioning rates for males 
and females combined varied with nestling age (P = 0.01) with rates lower for 1-4-day-old nestlings, increasing through 
day 6 and then declining for 7- 10-day-old nestlings. Provisioning rates varied with brood size (P = 0.026) with rates higher 
for broods of five than broods of three or four. Most prey items delivered to nestlings were grasshoppers (Orthoptera. 
68.1%). Received 8 October 2010. Accepted 22 January 2011. 
The relative contribution of males and females 
in provisioning nestlings varies among species of 
songbirds. One parent may provision nestlings at 
higher rates than the other parent in some species 
(Grundel 1987. Cockburn 2006); whereas males 
and females contribute equally in other species 
(Rytkonen el al. 1996. Schadd and Ritchison 
1998, Nordlund and Barber 2005). Variation 
among species suggests factors influencing pa¬ 
rental investment may produce different provi¬ 
sioning strategies in different species. 
Olson et al. (2008), in a comparative study 
involving data from 193 species of birds, reported 
parental care by males and females was negatively 
correlated; variance in male care was significantly 
higher than for female care. Thus, across species, 
variation in total care is primarily explained by 
dillerences in that provided by males. Several 
factors can influence male parental care. For 
example, males may reduce levels of parental care 
io pursue extrapair matings (Mitchell et al. 2007). 
Males in multi-brooded species may improve their 
reproductive success by provisioning nestlings in 
first broods, increasing the likelihood of their mates 
subsequently re-nesting (Stodola et al. 2009). Risk 
of nest predation may also influence male care as 
Bjomsiad and Lifjeld (1996) suggested provisioning 
by male Willow Warblers (Phylloscopus mxhilus) 
insured rapid growth of nestlings, early fledging, 
and reduced risk of nest predation. These and other 
•actors can potentially influence male provisioning 
behavior, but their relative importance in explaining 
variation in male care among different species of 
birds remains unknown. Thus, studies are needed of 
species that vary in behavior (e.g., mating strategies 
! Department of Biological Sciences. Eastern Kentucky 
University. Richmond. KY 40475. USA. 
2 Corresponding author; e-mail: gary.ritchison@eku.edu 
and number of broods per breeding season) and 
nesting ecology (e.g.. nest predation rates). 
Previous studies indicate several factors, includ¬ 
ing variation in brood size and nestling age, can 
affect provisioning behavior of both males and 
females. Parents, for example, may increase 
provisioning rates as brood sizes increase (e.g., 
Bedard and Meunier 1983, Conrad and Robertson 
1993) or there may be an inverse relationship 
between provisioning rate and brood size (e.g.. East 
1981, Tr£niont and Ford 2000). Some parents 
provision nestlings at similar rates throughout the 
nestling period (East 1981. Bedard and Meunier 
1983, Schadd and Ritchison 1998), while others 
cither continue to increase provisioning rates as 
nestlings grow (Nordlund and Barber 2005) or 
increase provisioning rates through the mid-nestling 
period before reducing rates a few duys before 
fledging (East 1981. Conrad and Robertson 1993). 
Grasshopper Sparrows (Ammodramus savan- 
narum) are socially and genetically monogamous 
(Ammer 2003), and typically breed in grasslands 
and lightly grazed pastures (Vickery 1996). These 
sparrows nest on the ground with clutch and brood 
sizes ranging from three to five and typically have 
low nesting success (25-50%) (Vickery 1996). 
Grasshopper Sparrows arc also multi-brooded (2-3 
nests/breeding season) (Vickery 1996). Both males 
and females provision nestlings (Vickery 1996), 
but the relative contributions of each are unknown. 
The objectives of our study were to examine the 
possible effects of brood size, brood number, and 
nestling age on the provisioning behavior of male 
and female Grasshopper Sparrows. 
METHODS 
Study Area .—Our study was conducted from 1 
May to 8 August 2002 and 30 April to 29 August 
515 
