Mitchell et al • DICKCISSEL NESTLING PROVISIONING 
303 
Nestling age (days) 
020 
0 18 
016 
0.14 
012 
0.10 
0.08 
* 
i 
Observer No 
present observer 
0 20 
0 18 
0 16 
0 14 
0 12 
0 10 
0.08 
i i 
Male No Male 
FIG. 2. Mean biomass (least-squared means ± SE) delivered to Dickcissel nestlings of various ages, buffer locations, 
and with/without observers in north-central Mississippi (USA). May to August 2008-2009. 
FIG. 3. Proportion of total number of arthropods 
observed on videos (dark bar) and collected in sweep nets 
(o Pen bar) from different habitats available to nesting 
bickcissels in north-central Mississippi (USA), May to 
August 2009. 
However, adults may have made some other, more 
subtle changes to meet increased demand. Biomass 
delivered and foraging distance may have in¬ 
creased with increasing nestling age (P = 0.161 
and 0.159. respectively), hut these differences were 
not significant. Possibly, these were small, but 
biologically important responses that may have 
been significant with a larger sample. A likely 
explanation is that parents attempted to meet 
increased demand by searching farther for larger 
prey items. Increasing prey size may have allowed 
adult Dickcissels to avoid energetic costs that more 
frequent trips would have entailed. Wc did not 
observe feeding behaviors past nestling age of 
7 days, and it is possible that biomass delivered 
continued to increase via changes in prey size and 
taxa. 
Dickcissel prey selection favored Orlhoptera, 
similar to other diet studies of grassland birds 
(e.g.. Kaspari and Joem 1993, Kobal et al. 1998). 
However, selection of Lepidoptera and Coleoptera 
prey was comparatively less in our study. 
Orthoptera may have greater protein (e.g.. Robel 
