Chan Yoke Meng was photographing a male Scarlet-backed Flowerpecker (Dicaeum cruentatum) feasting on the succulent fruits of Singapore Rhododendron (Melastoma malabathricum) when the bird suddenly defecated.
What came out from the vent (the external opening of the cloaca) was a string of sticky, blackish waste.
Being sticky, the blackish mass was stuck to the bird’s vent. It had to wipe its posterior against the branch to get rid of it. This effectively transferred the blackish mass to the branch.
Obviously the flowerpecker had been eating mistletoe fruits whose seeds are sticky. Being semi parasitic and growing from branches of other plants, the seeds need to be stuck to branches to germinate and develop LINK.
However, mistletoe seeds when excreted are covered with whitish sticky mucilage, not black, as seen here LINK.
We consulted Francis Lim, a student of local mistletoes LINK to find out whether eating fruits of certain species of mistletoes can result in such black excrements.
Back came the reply: “… I have not come across such dark-coloured seeds at all in my field observations. …The Singapore Rhododendron fruits do have a staining purplish dye and the photographer may be right in believing that this probable stained the droppings. Flowerpeckers do feed on various fruits, including different species of mistletoes and deposit the seeds together. Perhaps the next time he encounters such droppings he should collect, wash the seeds and germinate them to determine the mistletoe species.”
Chan Yoke Meng & Francis Lim