We compared differences in feather regeneration ability, energy budgets, organs levels, and heat regulation in molting Tree sparrows (Passer montanus). After one week of adaptation to laboratory conditions, thirty adult birds were assigned to three groups including control (CF, n=10), remove flight feathers (FF, n=10) and remove tail feathers (TF, n=10) by body mass and SPSS Tools. All three groups were monitored over a four-week period while exposed to similar environmental conditions. On a daily basis we measured food and water intake, the numbers of defecations, fecal mass, and so on. Feathers had strong regenerative capacities, and flight feathers were also important in heat regulation. The level of energy budget of birds declined (P < 0.001). FF and TF groups declined 19.77% and 7.17% in energy intake, 18.79% and 6.47% in digestible energy, 18.73% and 6.46% in assimilation energy, 28.66% and 13.35% in fecal energy, 26.95% and 7.43% in cooling heat energy of water metabolism, 33.71% and 14.40% in discharge frequency. FF and TF groups showed increases of 1.23% and 0.78% in digestion rate, and 1.35% and 0.84% in assimilation rate, respectively, compared with the CF group. Body weight in CF, TF and FF (P < 0.05) declined but body temperature showed no obvious change (P > 0.05). In terms of energy reserves, including blood sugar, muscle glycogen, body fat and water content, no significant difference (P > 0.05) was observed between the three groups, but liver glycogen content and body fat mass did differ (P < 0.05). Organ level, including heart, kidney, glandular stomach, small intestine, caecum and the length and quality of the total gastrointestinal tract showed a response to feather loss. Groups differed significantly in average daily water metabolism (P < 0.001). The minimum and maximum average number of defecations reached 56.11 times and 96.34 times, respectivel.
Under low levels of environmental stress, P. montanus showed strong feather regeneration capacities. The differences between regenerating flight feathers and tail feathers is due to distinct energy investment strategies and energy-saving strategies, also including energy consumption in flight and energy saving strategy of water metabolism heat loss reduction. There was an obvious decline in the level of energy budget and energy reserve of P. montanus. Discharge water from the cloacae with feces and urine mixture is a peculiar, effective and rapid thermal loss regulation mode among birds. Different feather parts have an influence on individual insulation capability and movement capacity, which proves to be a main reason for differences in water metabolism heat dissipation. Birds regenerating feathers showed reduced organs mass, improved organ efficiency, and reduced energy expenditure by organs. Energy consumption of organs is an integral part of individual energy budgets. Organ functional capabilities are closely related to individual energy intake, transfer and storage. Changes in organ quality, functional capabilities and energy consumption are the organ-level responses to body energy budget strategies. Distinct energy budget strategies were adopted by P. montanus in the same living environment with three feather structures.