Daily time and energy budgets in Whooper Swans Cygnus cygnus and Bewick's Swans Cygnus bewickii in the breeding season

Abstract

Both Bewick’s and Whooper Swans require little energy during incubation relative to birds in temperate latitutes (1.8 and 1.9*BM, as opposed to 2.5*BM). Whooper Swans expend considerable energy on flying. Their behaviour assists in maintaining them at low energy levels appropriate to the short cold summer and low calorific foods found in their sub-arctic breeding areas.