Energy Flow Through a Wintering Population of Tree Sparrows

A wintering population of Tree Sparrows (Spizella arborea) were studied in the winter of 1968-69 to provide information regarding energy flow. The Tree Sparrows were found to consume primarily Helianthus annuus seeds when they were available. When these seeds became scarce, Setaria sp. And Sporobolus sp. Seeds became the important foods. Caloric values for most food items were determined and non-ingested foods had significantly higher values than those removed from the stomachs of Tree Sparrows. Existence metabolism rates determined from laboratory food consumption experiments compared favorable to previously reported values for Tree Sparrows and other sparrow species. The efficiency of food assimilation for these experiments was high (87.5%) and closely approximated the food ingested. The estimated energy flow through the wintering population of Tree Sparrows in Kcal/m2/year was: 24.39 ingested, 5.41 lost in excreta, and 18.98 assimilated