Most people are familiar with the widespread Grey Heron which can be seen throughout the year at wetland sites. The slightly smaller and much gaudier Purple Heron is a summer visitor and more of a reedbed specialist, returning from Africa in small flocks between late March and early May. Not averse to long sea crossings, birds leaving Morocco are prone to displacement by easterly winds, a few even reaching the Azores when I was resident there. Reorienting parties flying east over the sea along the Algarve coast provide a memorable spectacle which I have been privileged to witness off my ‘seawatching’ point in the western village of Salema.
The Iberian breeding population suffered a major decline during the 20th Century, mainly due to the drainage of marshes, but there has been a partial recovery during the last fifty years. The Portuguese element was always relatively small and currently numbers less than five hundred pairs. The extent of their reedbed habitat is clearly the limiting factor as frogs form part of their diet and there is certainly no shortage of those! The long, slender neck and dagger-like bill make short work of these amphibians and other prey items, like fish and insect larvae. Very long toes spread the bird’s weight on floating vegetation near the water’s edge.
Many members of the heron tribe are colonial nesters, often in trees adjoining lakes and marshes. Nesting mainly in reedbeds, Purple Herons are not obviously colonial but at large sites nests can be quite close together. Less tolerant of disturbance than many of its relatives, birds adopt ‘the bittern posture’ when threatened by an intruder. This entails the neck and bill ‘frozen’ in a vertical position. Nest sites are readily abandoned, further limiting the success of a species already constrained by its specialised habitat requirements.
Outside the breeding season the species is more solitary, although birds sometimes roost communally. Larger flocks than those seen in spring can form during the autumn migration. I once saw more than 70 flying south together in Turkey.
Having few natural predators, the colourful plumage provides little in the way of camouflage and must be related to sexual display, although both sexes are identical.