Pellets from Tuas: 4. Analysis of 14 pellets

Melinda Chan made extensive collections of pellets from a tree-lined avenue in Tuas in January 2015. All pellets were covered with short grey hairs, most probably those of mice. One of these was larger than the rest, from which a near-complete skeleton of a mouse was extracted LINK. This was the only pellet that had an intact skull, all others had bone fragments and numerous loose teeth but no skull.

This large pellet was thought to have come from a Barn Owl (Tyto alba). The others, all smaller, were believed to have come from the nesting pair of Black-shouldered Kite (Elanus caeruleus), most probably the chicks.

However, an initial examination of four pellets LINK left a big question mark on the identity of the prey – as no skull was found. The presence of numerous molars and bone fragments that had holes of various sizes and shapes, added to the mystery of the prey identity. After all, the mouse bone fragments failed to deliver any loose teeth and these strange “holy” fragments.

Subsequently 14 pellets were examined (above) following earlier protocol. No complete skull was found in any of hese pellets. Many had the same types of fragments found in the earlier four pellets. In addition, pieces of jawbones with some teeth still attached were found (below)…

…and there were numerous loose teeth, molars actually, as well as incisors (below).

The image below shows the other miscellaneous bone fragments found in the pellets. An attempt has been made to label some of the bone fragments…

In the process of extracting the fragments, it was realised that the “holy” fragments were actually parts of the jawbones where the molars were once attached, leaving sockets that were earlier filled by the teeth roots. Once this was realised, it became obvious that all the pellets were from mice. It can thus be concluded that food fed to the chicks of the Black-shouldered Kites in the nest were mainly young mice.

This is supported by the fact that the incisors of young mice do not have the yellowish colour seen in older mice (above) – although in the image of the teeth given earlier, some of the lower incisors were just developing the colour.

According to field ornithologist Wang Luan Keng, skulls of young birds and mammals are not or only partially ossified. As such the skulls were easily crushed in the kites’ gizzards, leading to the molars and incisors being loosened from their sockets. The absence of intact skulls and jawbones also points to these bones being easily crushed.

Melinda Chan (pellets), YC Wee (images) & Wang Luan Keng (opinion)
Singapore
February 2015