Mitchell et al. • DICKCISSEL NESTLING PROVISIONING 
301 
TABLE 1- Variables examined with general linear 
models for Dickcisse! foraging in native grass field buffers 
in north-central Mississippi (USA). May to August 2008- 
2009. 
Variable 
F 
df 
P 
Provisioning rate (visits/nestling/hr) 
Nestling age 
0.98 
3. 40.4 
0.412 
Buffer 
0.01 
1. 63.0 
0.925 
Observer present 
7.97 
1. 237 
0.005 
Male helping 
15.60 
1. 97.9 
<0.001 
Year 
2.45 
1. 38.9 
0.126 
Biomass (g/nestling/hr), 2009 only 
Nestling age 
1.89 
3, 21.9 
0.161 
Buffer 
0.54 
1, 15.3 
0.475 
Observer present 
3.43 
1, 130 
0.066 
Male helping 
0.00 
I. 82.4 
0.922 
Foraging distance from nest (m/nest/hr) 
Cloud cover 
3.67 
4, 87.8 
0.008 
Wind speed 
3.09 
3, 92.8 
0.031 
Nestling age 
1.78 
3, 68.4 
0.159 
Buffer 
2.52 
1. 34.8 
0.121 
Nestling number 
0.32 
4, 33.4 
0.861 
Male helping 
1.05 
1. 68.6 
0.310 
Year 
0.56 
1, 51.8 
0.456 
-008; 157 in 2009). We observed 2.384 indiv idu.il 
provisioning events and recorded 2.417 prey items 
delivered to nestlings. Total filming hours for 
provisioning rales were 264.02 (124.35 in 2008; 
139.67 in 2009). We observed 822 foraging trips 
uVer 118.30 observer hours (56.93 in 2008; 61.37 
m 2009). 
Nestling Provisioning Rate. —Cloud cover. 
u ind speed, and temperature were not related to 
provisioning rates and were not included in 
subsequent analyses. Provisioning rates (mean ± 
^E.i were higher when a male helped (3.63 it 0.28 
with male; 2.64 ±0.18 without; F,.g 7 » = 15.60. 
V < 0.001; Table 1. Fig. 1) and lower when 
observer* were present (2.97 ± 0.21 with 
observer; 3.30 ± 0.20 without; F\z*n - 7.97. 
^ = 0.005). Provisioning rate of nestlings did not 
"itrease from 4 to 7 days (/•%.-«>.4 = 0.98. P = 
did not differ between buffer and non¬ 
buffer habitats (F,. M0 = 0.01, P = 0.925). and 
d,d not differ between 2008 (2.88 ± 0.28) and 
-009 (3.39 ± 0.23; F,. 3 *.y = 1-89, P = 0.126). 
Biomass Delivered.— Cloud cover, wind speed. 
:ind temperature were not related to biomass and 
Wcre dropped from subsequent analyses. Biomass 
provided to nestlings in 2009 was 0.124 ± 
0.005 g/nestling/hr. Biomass provided to nestlings 
Was less when an observer was present (0.120 ± 
0.012 g/nestling/hr) compared to periods with no 
observer present (0.138 ± 0.012; F u -u, = 3.43, 
P = 0.066; Table 1. Fig. 2). Nestlings received 
>50% more biomass on day 7 compared to day 4. 
but this difference was not significant (F 3 . 21.9 = 
I n9. P = 0.161). Biomass delivered did not differ 
between nests in buffer versus non-buffer habitats 
- 0.54. P = 0.475) and did not differ 
when males helped (F\.» 2 A = 0.00, P — 0.992). 
Prey Taxa .— 1 Orthoptera comprised nearly all of 
nestling diets in 2008 (91% of items) and 2009 
(86%). Less common prey (both years combined) 
included Lepidoptera (7%) and spiders (Araneae, 
4%). Prey (Orthoptera. Lepidoptera. Araneae) 
provisioned by Dickcissels were not the most 
available taxa in surrounding habitats in 2009 
(Fig. 3). Dickcissels preferentially selected Or- 
thoptera (w = 3.71. P < 0.001) and avoided 
Araneae (w = 0.22, P < 0.001), Coleoptera (w = 
0.02. P < 0.001), Diptera (>r = 0.06. P < 0.001), 
Hemiptera (»• = 0.00. P < 0.001). and Hyme- 
noptcra {w = 0.02, P < 0.001) based on selection 
ratios. Selection of Lepidoptera (w = 1.33. P = 
0.436) and Mantidae (tv = 4.37, P = 0.491) 
was not different from availability. We restricted 
subsequent analyses of prey taxa to Orthoptera. 
Lepidoptera. and Araneae because they comprised 
>99% of the prey items. 
Dickcissels in 2008 were more likely to bring 
Orthoptera as nestling age increased (94% of total 
items on day 7 vs. 91% on day 4; F 4.000 = 
P = 0.028; Table 2). when nests were positioned 
in buffers versus adjacent habitats (94 vs, 91%; 
F, ft(H) = 4.91. P = 0.008), when observers were 
absent (95 vs. 90%; F 2 , m = 7.65. P < 0.001). 
and when nests contained <5 nestlings (94-100% 
when > 4 nestlings vs. 88% with 5; = 2.41, 
P = 0.026); the size of these actual differences 
was small. Males were substantially more likely to 
bring Lepidoptera (21% for males vs, 4% for 
females) and less likely to bring Orthoptera (77 
vs. 94%; F 2.600 = 7.59. P < 0.001). None of these 
factors influenced prey taxa brought to nestlings 
in 2009 (F = 0.04-1.53, P = 0.166-0.992). 
Prey Size .—Adults were more likely to bring 
medium versus small prey items as nestling age 
increased in 2008 (med. items = 73% of prey items 
on day 4 vs. 80 and 79% on days 5 and 6; F 4.640 = 
3.36. P = 0.010; Table 2). Adults were more likely 
to bring large items as nestling age increased in 
2009 (e.g.. 30% on day 7 vs. 11 % on day 4; F 6 ./ 0 26 
= 6.26. P < 0.001; Table 2, Fig. 4). Males in 2008 
were more likely to bring medium prey compared 
