WINDEN J VAN DER, P W VAN HORSSEN & M J M POOT (2010) Post-breeding night roosts and foraging areas of Purple Herron Ardea purpurea in The Netherlands. LIMOSA 83 (3): 109-118.

Very little is known about the postnuptial ecology of the Purple Heron. In 2007 and 2008 in total 16 Purple Herons (12 adults) received satellite transmitters. During the breeding season these herons used feeding areas at a distance of 1.5-15 km from the breeding colonies. However, after breeding the adults left the colony sites for a permanent stay in these feeding areas, roosting close by at night. These feeding areas are mostly agricultural grasslands and peat marshes. This finding initiated a field search for Purple Heron night roosts in the Groene Hart region of the Netherlands. In total 483 Purple Herons were counted on roosts. In two sample areas totalling 110 km2, all roosts were located and herons counted. The average number of birds at a roost was 9.2. Based on the average heron densities in these sample areas (1.8 and 2.8 herons/km2), the total number of Purple Herons in the Groene Hart could be estimated at 1400- 2000, closely matching the estimated breeding population including fledglings. This confirms that almost all Purple Herons stay for some time in feeding areas prior to southward migration. From a conservation perspective it is important to note that only 10.5 % of the feeding habitat is situated within Natura 2000 sites. Potential future impacts on the feeding habitat are discussed. Purple Herons start their migration to Africa around the end of August. In contrast to previous assumptions, the herons do not depart from their breeding colonies, but directly from the feeding areas. This explains the high numbers observed during evening migration counts at Ridderkerk (478-694 departing herons in 2002-05). In the feeding areas north and northeast of this site, 470-930 Purple Herons are estimated to stage. The 900-1100 herons from other feeding areas will probably migrate mainly to the east of this counting site. This means that Purple Herons depart from the Netherlands in a broad front with some concentrations due to landscape characteristics and aggregation into migratory flocks.

[pdf only for members] [dutch summary]