The rapid mass loss was not, therefore, caused simply by the effort of feeding. Females lost mass most rapidly when brooding young chicks, but before the peak food requirements of the brood were attained. Only females brooded, whilst both sexes fed the nestlings in roughly equal proportions. The brood and both sexes of Hirundo rustica parents were heaviest when insect prey was plentiful.
The lack of significant improvements in growth or health with the addition of another demand feeder indicated that using more than one feeder per 5.5 m of raceway length is unnecessary for culture of juvenile rainbow trout. However, since fish from the two-feeder treatment did not differ from controls, demand feeding per se did not improve fin condition relative to fish that were fed by hand, four to six times per day. Fin condition assessed by measuring relative fin length was better in the single feeder treatment than controls for caudal and ventral fins in the last sample. Fin index values did not differ among the feeding methods. Over time, hematocrit decreased from 48.6 to 45.0%, and the fin index increased from 0.80 to 1.57. Several parameters differed significantly over time, but no trends were observed except for the fin index and hematocrit. Necropsy-based health and condition profiles were conducted three times during the rearing period, and results indicated that fish were generally normal and healthy in all treatments. coefficient of variation of total length. Size variation did not differ among treatment groups, as assessed by comparing the.
Mean weight, total length, mortality, and feed conversion were not influenced by the method of feeding. Fingerling rainbow trout, Oncorhynchus mykiss, were fed for 133 d by one of three feeding methods: one demand feeder per 5.5 m of raceway, 2 demand feeders per 5.5 m of raceway, and hand-fed controls. Blue tits continually monitored the begging behaviour of their offspring and responded accordingly by adjusting their feeding rate, with immediate consequences for prey choice. This suggests that parents in the supplemented group could use more time to reach good feeding sites or, more probably, increase their prey selectivity. Food-supplemented parents, but not controls, took larger larvae when they stayed away from the nest for longer. Females often responded to low brood demand by returning to the nest without food. Changes in provisioning rate had effects on both the type and size of prey brought to the brood. parents not provided with additional food). Provisioning rate returned to the usual levels as soon as the chicks started begging again, but supplemented parents took less time to do so than controls (i.e. Parents spent significantly longer away from the nest immediately after uttering these feeding calls. When chicks did not beg for food, the parents solicited them with a particular call to make them open their beaks. Videotaping revealed that parents changed their provisioning rate as an immediate response to the absence of begging. An additional feeding experiment allowed a comparison between the behaviour of parents rearing their brood under normal and supplemented feeding conditions. I investigated the short-term regulation of parental provisioning rate in blue tits by videotaping the parents at the nest.
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