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The Purple Heron (Ardea purpurea) is a large and elegant heron with long, snake-like neck. Adult has a black cap and rufous neck with black line running down side of it. The flanks and scapulars are reddish-purple. The wings and back are purplish-grey. The length is about 95 cm. Immature individual is generally sandy rufous with greyish wings.
Both sexes are more or less alike, but the length of wings and bill is slightly longer in some males. However, this feature is difficult to gauge in the field. Worth mentioning that there are some variations in colouration depending on geographic location. The above description is specifically for Southeast Asian birds.
Similar species includes the Grey Heron that can be easily identified by its combination of greyish-white and black plumage. Misidentification may happen when the birds are in flight because both species are large with similar flight pattern, and the neck is tucked in forming an s-shape.
The Purple Heron is a quiet bird. It utters a croaking kraak usually on take-off.
Distribution and Habitat
The Purple Heron has an extensive distribution, being found in Europe, Africa and Asia. Throughout its range, four subspecies are recognized.
It prefers damp habitat particularly places with standing waters and dense emergent vegetations. It is also found alongside rivers, reservoirs and paddy fields. In coastal areas, it frequents mudflats and mangroves.
A stand-and-wait hunter, the purple heron is often spotted stand motionless in shallow water on the lookout for prey. It catches its prey swiftly using its strong and sharp bill. The advantages of the long, flexible neck in hunting is apparent as it gives the heron longer reach and greater field of view. Its prey includes fishes, amphibians, invertebrates and occasionally small mammals and birds as well.
The nest is a platform made of sticks and reeds in trees, often very close to water. Both sexes participate in rearing the young. The number of eggs laid varies between regions, but they are known to lay up to eight eggs. The eggs are incubated for nearly a month and the chicks become independent in about 45-50 days.
The Purple Heron eggs hatch asynchronously. The female starts incubating prior to laying the last egg, resulting in older eggs hatch earlier than the later ones. Scientists believe this is an adaptation in response to fluctuating food supply. In period where food is scarce, older hatchlings are better fed and in turn their survival is higher than their younger siblings. Eventually the numbers of offspring that survive correspond with the amount resource available in the environment. In other words, the parents produced the best possible number of offspring that the food resource permits. However, when food is abundant, younger hatchlings may also survive.
Birds from Europe migrate south, passing through the Iberian Peninsular to mainly West Africa. Some fly to as far as Kazakhstan and Pakistan. Birds in North East Asia migrate to Korea, South China, Japan, Thailand and Peninsular Malaysia. The journey is not without hazard though. Some individuals were reported shot dead by illegal poachers, while some lost their way and plunged into the Atlantic Ocean. Still others were caught in sand storms and died in Africa.
Status and Threat
This species is categorized as Least Concern in the IUCN Red List. Habitat destruction is the main threat. For example reed harvesting has resulted in loss of breeding sites.