Body Size Mediated Coexistence in Swans

Table 2

Comparison of tundra and trumpeter swan days that the tuber resource (Table 1) could potentially support and the number of tundra and trumpeter swans actually observed foraging in the four study wetlands. We assume tundra swans require 258.5 g tubers/day (twice basal metabolic rate) and trumpeter swans require 361.8 g tubers/day. Swans are likely to ingest more tuber biomass per day during staging to maximize energy intake.

Site	Calculated tundra swan days on shared resources^a	Actual tundra swan days^b	Calculated trumpeter swan days on exclusive resources^a	Actual trumpeter swan days^b
Unit 1	189,000	90,000	0	0
Unit 2	1,657,000	418,000	0	0
Unit 4	705,000	127,000	0	0
BRC	2,588,000	821,000	166,000	600
Total	5,138,000	1,456,000	165,000	600

 ^aCalculation of swan days does not take into account that swans will not completely deplete the tuber resources in the sediments. Calculations account for 25% tubers lost to decomposition during dormancy.
^bCalculation of actual swan days takes into account days that the wetlands were frozen shut and swans were not foraging.