Pre-migratory behaviour of the purple heron in the Netherlands

Doi: http://dx.doi.org/10.13157/arla.59.1.2012.3

Authors: Jan VAN DERWINDEN, Peter W. VAN HORSSEN, Martin J. M. POOT and Abel GYIMESI

E-mail: j.van.der.winden@buwa.nl

Published: Volume 59(1), June 2012. Pages 3-15.

Language: English

Keywords: Ardea purpurea, breeding areas, feeding areas, migration, post-breeding behaviour, premigratory behaviour, satellite transmitter and stopover site

Summary:

Birds performing long-distance migration without substantial refuelling en route rely on fat reserves accumulated in the post-breeding, pre-migratory period. In order to fill a knowledge gap in the pre-migratory behaviour of purple herons Ardea purpurea, a species conducting a 3,500-4,000 km migration journey within 5-7 days, 12 adult and four juvenile purple herons were equipped with satellite transmitters in The Netherlands. The birds were followed during and after the breeding period until they departed for their migration. Based on the recorded positions, the location and the size of pre-migratory feeding areas were identified, as well as the duration herons used these sites. In addition, the location of and the distance flown to and from night roosts could also be defined. The results revealed that failed breeders started migration at the same time as successful breeders resulting in a longer pre-migratory period. After fledging, juveniles showed an initial “search period” before settling down at a final premigratory site, which resulted in later departure to Africa compared with adults. Most of the dusk- and daylight period (amounting altogether to 15-18 hours) was spent at the feeding sites. After breeding, most adults remained to use the same feeding areas but switched from sleeping in the colony to night roosts within feeding areas, likely to minimize the daily flight costs. Based on the daily foraging time, the pre-migratory period seems to be sufficient to deposit reserves for a migration journey of several thousand kilometres. Above this, our results generally highlight the importance of high-quality premigratory feeding areas for long-distance migrants without extensive stop-over periods.

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