Timing and duration of spring staging of the eurasian greater white-fronted goose (anser albifrons albifrons) in relation to sex, age and progress of migration season

Abstract

Ameans to accumulate fat and nutrient stores to invest in both migration and their bree-dingattempt in the tundra zone. We studied the influence of possible factors (age, sex, progress of migration season) on the stopover duration of one such species, the Eurasian Greater White-fronted Goose (Anser albifrons albifrons), by analysingrecords of 1,115 neck-banded birds spotted at their Biebrza Basin stopover site on spring migration in Po-mfc land. As expected, because most mature birds are paired, there were no differences be-^Hf tween the sexes in stopover duration. Generally, adults stayed for shorter periods than immatures and stopover duration was shorter later in the season. Data from individuals of (JSB^ known age showed that the rate of decrease in stopover duration with season was faster among older than younger geese. Immature birds, still not ready to breed, do not face the pressure to attain breeding condition and therefore may stay longer in the stopover areas. We think these patterns may reflect the greater experience of older birds, as well as the stronger pressure on them to reach the breedinggrounds as early as possible. As the bree-dingseason approaches and foragingopportunities at migration sites further up the fly-way become more accessible and of higher quality, geese stay for shorter periods later in the season.