Adler and Ritchison • PROVISIONING BY GRASSHOPPER SPARROWS 
517 
TABLE 1. Effects of nestling age on provisioning rates 
and the prey biomass (number of adult visits/hr x mean prey 
size x mean number of prey) delivered by male and female 
Grasshopper Sparrows (combined). 
Nestling sge (days) 
Provisioning rate (visils/hr)* 
Prey binmasVhi 
1-2 
2.7 ± 0.5 (a) 
5.5 ± 1.1 (a) 
3 
3.8 ± 0.5 (ab) 
6.9 ± 1.3 (ab) 
4 
4.9 ± 0.4 (abc) 
10.0 ± 1.0 (ab) 
5 
6.0 ± 0.8 (be) 
12.7 ± 1.9 (b) 
6 
6.8 ± 0.7 (c) 
13.8 ± 1.2 (b) 
7 
5.5 ± 0.6 (be) 
11.1 ± 1.5 (ab) 
8-10 
5.0 ± 0.6 (abc) 
11.0 ± 1.8 (ab) 
' Mean ± SE (means with the same letter are not significantly different; 
SNK test, P < 0.05). 
There was no difference in the amount of prey 
biomass delivered to nestlings by males and 
females (F, I3 = 0.01, P = 0.93) with means of 
4.64 ± 0.35/hr for females and 4.70 ± 0.31/hr for 
males. Interactions between gender and brood 
number (first vs. second nest; P - 0.33), gender 
and nestling age (P = 0.57), and gender and brood 
size (P = 0.72) were not significant. Male and 
female Grasshopper Sparrows did not differ in 
either provisioning rates or biomass delivered and 
no interactions were significant. Thus, we as¬ 
sumed that unidentified adults visiting nests were 
as likely to be males as females and used total 
provisioning rate (male visits + female visits + 
visits by unidentified adults) and total prey 
biomass delivered for subsequent analyses. 
Nestling Age.—Provisioning rates of adult 
Grasshopper Sparrow's varied with nestling age 
lf M 4 = 3.2, P = 0.01) with rates lower for 1-4 
day-old nestlings, increasing through day 6 post¬ 
hatching. and then declining for 7-10 day-old 
nestlings (Table 1). Prey biomass delivered varied 
with nestling age (F 644 = 2.4, P = 0.042) with 
‘‘raounis lowest for 1-3 day-old nestlings, in¬ 
creasing until day 6 . and then declining for 7-10 
day-old nestlings. Differences in prey biomass 
delivered to nestlings of different ages were 
primarily due to differences in provisioning rates 
as *here were no significant differences in cither 
die size of prey (F 644 = 0.9. P = 0.50) or number 
of Prey (F 6 44 = |.l, p = 0.36). 
Brood Size. — 1 Total provisioning rales by pairs 
°l Grasshopper Sparrows varied with number of 
nestlings (F 215 = 4.7, P = 0.026) with higher 
rates (SNK tests, P < 0.05) for broods of five (6.7 
- 0.5/hr) and similar rates for broods of three (4.2 
i 0.4/hr) and four (4.7 ± 0.4/hr). We found no 
differences among different brood sizes in number 
of visits by adults per nestling (F 2 a ~ 0.6, P = 
0.62). Prey biomass delivered by adults varied 
with number of nestlings (F 2 ,i 5 — 5.5, P = 
0.016); the amount of prey biomass delivered was 
significantly different (SNK tests. P < 0.05) for 
broods of three (7.2 ± 0.7/hr), four (10.8 ± 1.0/ 
hr), and five (14.1 ± 1.0/hr). We also found no 
difference among broods of different sizes in 
amount of prey biomass delivered by adults per 
nestling (F 2 , 2 = 0.1, P = 0.90). 
Brood Number. —We found no difference in 
provisioning rates between nests (Fi j3 = 1.0, P = 
0.39) for pairs of Grasshopper Sparrows (n = 4) 
where both first and second nests were video¬ 
taped. We also found no interaction between nest 
number (first and second nests) and nestling age 
(P = 0.49), indicating that adults provisioned 
nestlings of different ages at similar rates for both 
nests. 
Prey Items .—We either could not ascertain if 
adult Grasshopper Sparrows delivered prey or 
could not identify the prey item during 771 of 
1,744 nest visits (44.2%). Adults visited nests 
without prey 84 times ( 8 . 6 % of visits) and 
delivered 960 identifiable prey items during 889 
visits. One prey item was usually delivered per 
visit (n = 820 visits, or 92.3%) with two items 
delivered during 67 visits (7.5%) and three during 
two visits ( 0 . 2 %). 
Most prey (n = 960) were grasshoppers 
(Orthoptera, Acrididae; n = 654, 68.1%), larvae 
(n = 217, 22.6%), crickets (Orthoptera, Gryllidae; 
n = 54, 5.6%), and moths (Lepidoplera, n = 18, 
1.9%). Other prey items included seven bees 
(Hymenoptera, Apoidea), six beetles (Coleop- 
tera), and four spiders (Araneae). Mean length 
of grasshoppers fed to nestlings was 24.4 mm and 
the mean length of crickets was 21.8 mm. 
DISCUSSION 
Male and female Grasshopper Sparrows provi¬ 
sioned nestlings at similar rates and delivered 
similar amounts of prey biomass. Similar results 
have been reported for other songbirds (e.g., 
Schadd and Ritchison 1998, Nordlund and Barber 
2005). However, in other species where both 
parents provision young (e.g., Bedard and Meu- 
nier 1983, Bouwman et al. 2005, Falconer et al. 
2008), females provisioned at higher rates than 
males. Grasshopper Sparrows, at least among 
populations in southern West Virginia (Ammer 
2003), appear to be both socially and genetically 
