Characteristics of ponds used by trumpeter swans in a spring migration stopover area

Abstract

We investigated pond habitat use by trumpeter swans (Cygnus buccinator) at spring migration stopover areas in southern Alberta in 1999 and 2000. Spring migration stopover areas may be critical to gaining energy stores required for successful breeding, but no studies of trumpeter swan migration habitat have previously been published. We conducted counts of trumpeter swans on 13 ponds located west of Calgary, Alberta, Canada, and divided the ponds into three groups based on their use by trumpeter swans (consistent high use, variable use, and consistent low/no use). We determined properties of all ponds, including pond area <1 m deep, distance from roads, days ice-covered while trumpeter swans were present, pH, conductivity, total phosphorus, percent macrophyte cover, and rhizome plus tuber dry mass per square metre. We used forward-stepping discriminant function analysis to determine which pond properties were most consistent with trumpeter swan use. Consistent high-use ponds had the greatest rhizome plus tuber dry mass per square metre and high conductivity. Ice cover also influenced pond use. Potamogeton pectinatus was the dominant macrophyte in all consistently used ponds. Our results are important for identifying ponds favoured by trumpeter swans and to ensure that adequate habitat is available during spring migration.