Nesting Grey Herons: 6. Chick development

“All the nests in the heronry were built at high level. To observe the eggs was quite impossible. It was uncertain how many eggs were laid and how many were hatched. To answer such questions, a helicopter view from top down is needed. Or one must be blessed enough to see an egg shell being picked up to have knowledge of the eggs hatching. Well, on one occasion, an observer was lucky enough to witness an adult heron picking up an empty egg shell in one of the nests and eating it. One of its eggs must have hatched!

“Newly hatched hatchlings were difficult to sight. After hatching, the hatchlings seemed quite inactive and must have spent most of their time sleeping or resting. They were always hidden from view; either due to their inactivity or there was an adult sitting on them. Probably, this may be a defence strategy by Grey Herons against predation of their young. Observers can only hope to have rare glimpses of hatchlings when the adults were checking on them and they happened to raise their heads.

“After weeks of seeing only adults in the heronry, small hatchlings finally made their appearance. A smal, hatchling had momentarily raising its head to peep out from its nest (above left). Long fluffy down feathers covered the hatchling when it was first sighted. The selected images illustrate the chicks’ growth and development from a particular nest. The chicks were shown with an adult initially, and later without. Separately, image of a chick that was probably 3 to 4 weeks old, from another nest, is also attached as it shows pin feathers that were developing on the underside of the outstretched wings (above right).

“Two weeks after the first sighting of hatchlings from this nest, two young chicks could be seen (below left%r9. They were growing so fast that they appeared to have more th!n double their size. Their feathers were fast developing and their fresh plumage was darker than the adults. The crown was black but part of the head and long folded necks appeared to be dark mahagony in colour. Down feathers were still clearly visible. The lower mandible was pale yellow and upper mandible dark.

“One week later, the chicks had grown even bigger and were becoming more active (above right). They appeared to learn fast and had started to imitate the adults’ behaviour such as preening, stretching, and even sunning. Down feathers were less visible and the plumage seemed well developed. However, with wings outstretched, pin feathers were clearly visible as they were still developing on the underside of the wings. It appeared that these and the tail feathers were the last to develop. The plumage had turned lighter in colour and the mahagony on the neck had almost disappeared. The lower mandible had turned more yellowish, but the upper mandible was still dark.

“Five weeks after their first sighting, the chicks had grown to almost the fullksize of their parents. By now, the chicks were sometimes left alone to fend for themselves as the 24-hour parental guard duties had stopped. Feeding duties, which were carried out by both parents, continued. The chicks were now more active and had started to share or learn some responsibilities. They were observed to retrieve sticks from their parents, which they then placed into the nest without supervision.

“After six weeks, the chicks had fully developed to reach the full size of an adult (above left). Down feathers were no longer visible. The feathers on the underside of the wings had fully developed with pin feathers no longer visible. The chicks were transforming into juveniles. With more active flapping and exercising of their wings, they were certainly getting ready to fledge soon. True enough, after seven weeks, one of the chicks had clearly fledged as only one chick could be seen in the nest (above right).

Kwong Wai Chong
Singapore
15th January 2011

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  1. […] This post was mentioned on Twitter by pasir ris, Ivan and Ivan Kwan, NC_Birdwatch. NC_Birdwatch said: via Bird Ecology Study Group-Nesting Gray Herrings http://bit.ly/huU5tP […]

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