Nest raiding

April 22nd was Earth Day. It was quite busy for Timothy Pwee in many ways. In the morning around 9.30am, one of the Nature Society (Singapore)'s Education Group volunteers, Hui Ping, spotted an eggshell with a fully developed embryo on the grass in the Palm Valley of the Singapore Botanic Gardens. Together with Goh Si Guim, Tim went to take a look. They found several clusters of light blue eggshell fragments around one of the palms. There was one with a fully developed embryo totally out of the shell.

As Tim narrates: “Because the eggshell had cracks radiating from more than one spot, we suspected that the egg had been attacked rather than just dropped from the nest. Another almost complete shell on the other side of the palm appeared to be around one and a half times larger. This larger eggshell did not have speckling. Wang Luan Keng suggested that this shell belonged to the Black-naped Oriole (Oriolus chinensis).”Si Guim continues: “Besides the shattered egg and the spilled embryo of an incompletely developed bird, there were other empty shells around the tree. All were empty. They could be empty shells ejected from the nest(s) above, meaning that the chick had hatched out and fledge. Or the eggs could have fallen and the content decayed some time ago.

“Please note the markings on these two shells (image above). The one on the right does not have brown specks, suggesting different species of birds nesting among the many woody leaf bases on one palm tree. There were many Asian Glossy Starling (Aplonis panayensis) visiting these palms.

“Would forensic birding reveal how these eggs got onto the ground? Were the eggs cracked by raiders or did they break up on impact with the ground i.e. whether they were ejected by parasitic birds or the nest were raided by other birds.

“In the 90s, while exploring the still untouched Bidadari Cementery (Muslim side), I encountered an oriole raiding the nest of other birds. Egg yolk was seen dripping from the branches. I also had a close encounter with the Changeable Hawk-eagle (Spizaetus cirrhatus), now that I recall those nostalgic moments."

R. Subaraj has this to say: "We know that crows raid nests of birds and consume the eggs and chicks. However, I have not heard of orioles doing so too! We must not rule out the Plantain Squirrel as being another potential culprit (especially at the Singapore Botanic Gardens). However, we need documentation to prove whether they simply are destructive or if they actually feed on the eggs.

Input by Timothy Pwee and Goh Si Guim, ID by Wang Luan Keng. Top image by Tim, the rest by Si Guim.

You can view Tim's posting here.