In an earlier post, Angie Ng described in detail how a male Scarlet-backed Flowerpecker (Dicaeum cruentatum) deposited a string of sticky seeds on her sui mei (Wrightia religiosa) plant thus:

“After comfortably positioning itself transversely across the branch, it turned its head… then it awkwardly stretched apart its legs, lowered its little body for a second or two and with a swagger, it moved a few steps to the left. With that quick swaggering action it wiped off a string of six gluey mistletoe seeds onto the branch of my sui mei.”

Now, Chan Yoke Meng has documented another behaviour by a female Scarlet-backed Flowerpecker excreting Macrosolen cochinchinensis seeds. These mistletoe seeds were excreted one at a time. Each seed was enclosed within a tough gummy substance that remained unchanged after passing through the bird’s alimentary canal. The seeds were excreted in a string - any one seed attached to the one before and the one after by this gummy substance.

The bird had no difficulty expelling the seeds from the its vent, that is, its posterior opening. The problem was to get rid of the seeds after they emerged. With all the gummy substances around, the seeds remained stuck to the bird. In Angie’s case, the bird rubbed its posterior end on the branch it was perching on.

Meng’s observations show the birds actively removing the sticky seeds with the help of its bill and feet (of course, not using both feet at the same time, ha ha). The action was rapid and he missed documenting the most interesting scenes. However, he managed to record the bird entangled with strands of gum stuck to its bill and feet (see panel above). Two seeds that the bird managed to remove remain stuck to the branch behind it. Note the translucent globs of gum still attached to the seeds.

Earlier posts on mistletoes include accounts on the plants, naturalist’s account, observations of a sometime bird watcher, and pollination by Hanging Parrot.

KC Tsang was at Neo Tiew Lane on 2nd September 2007 when he came across the nest of the Peaceful Dove (Geopelia striata) (above). There was an adult in the nest together with two chicks. But what he noticed was the filth of the nest periphery, so much so that he wrote, “…this nest made of shit, bird shit. And the best thing is that it is all orderly, and properly arranged.” Tongue-in-cheek he continued, “Now the question is, how long did it take to collect all these faecal matter to build a nest, is all the faecal matter from the same two adults, is it not very unhealthy for the chicks, but looks like it is not so. Has anyone else notice this use of faecal matter as nesting material in other species of birds…?”

The Peaceful Dove constructs a very simple nest, actually a more or less flat platform of twigs. The adults take turn incubating and brooding, remaining in the nest all the time until time to change shift. Even when they are ready to discharge wastes, they do not leave the nest. They just point their posterior away from the nest and shoot.

In most cases the birds leave some mess around the nest edge (left). But not the massive wastes seen in the nest above. As KC puts it, “Propulsion unit not strong enough?” or is it because of “First generation equipment?”

Faecal wastes attract harmful organisms, from mites to bacteria. And eventually, it is the chicks that get infected.

So what do most birds do? Many take great care to remove wastes from nesting chicks via faecal sacs, as seen with Oriental White-eye (Zosterops palpebrosus), Scarlet-backed Flowerpeckers (Dicaeum cruentatum) and Olive-backed Sunbirds (Cinnyris jugularis).

But not the Peaceful Dove!

I suppose unhygienic birds will produce weak chicks. And weak chicks may not breed. The net result will be the end of this line of unhygienic birds.

Input by KC Tsang and YC; images by KC (top) and YC (bottom).

The chicks of most passerines enclose their wastes within a flexible bag known as a faecal sac. The parent birds meticulously remove these sacs and dispose them some distance away from the nest. These sacs help keep the nest sanitary and the absence of wastes around the nest will not attract unwelcome attention, especially from potential predators.

In the Scarlet-backed Flowerpecker (Dicaeum cruentatum), the adult birds attempt to remove these sacs as and when they appear from the cloaca of the chicks. But in many instances they are not able to cope with the situation and the chicks simply excrete the sacs out through the opening of the nest.

This is not the case with the Oriental White-eye (Zosterops palpebrosus). During the first two days after hatching, the adults will enter the nest, pick up the faecal sacs and swallow them. It is believed that at this early stage of the chicks’ development they are not able to totally digest the food fed to them. The adults thus recycle what the chicks excrete to benefit from the nutrients that are still present in the faeces.

However, as the chicks get older and their digestive system becomes more efficient, they are able to extract most of the nutrients in the food. The adult birds thus simply remove the sacs and dump them some distance away from the nest.

From observations, it was noted that the white-eye chicks excrete only when an adult was around and that they would do this in an orderly way. The moment a chick stuck its posterior up, the adult would immediately move near and grabbed the faecal sac directly from the cloaca (above). The adult would then fly off and dispose of it some distance away. In the example shown on the right, the adult picked up the sac but somehow dropped it.

Is it a wonder then that the nest of the Oriental White-eye is always clean?

Input by Melinda Chan and YC, images by Chan Yoke Meng.

How do birds deal with wastes generated by their nestlings? Those of the Peaceful Dove (Geopelia striata) seen on the left obviously do not practice sanitary hygiene, soiling their nest with their faeces.

Some parent birds actually eat the faeces during the first few days after the nestlings hatch. At this early stage, the droppings are rich in partially digested food as their intestines lack the necessary bacteria for complete digestion.

As the nestlings grow older and the bacteria set in, the faeces need to be disposed of. Many nestlings simply turn around, point their posteriors away from the nest and fire away. Depending on the aim, they may keep the nest clean or end up fouling it.

Others dispose of their waste via faecal sacs. These sacs are made of strong mucous that the parent birds can easily pick and dispose of some distance from the nest. Robins and bluebirds have been reported to fly off and drop the sacs some distance away. Grackles almost always drop faecal sacs over water but when they nest in backyards where there are no rivers or streams nearby, they tend to drop them in swimming pools.

A recent study in Georgia, USA found that Eastern Bluebird (Sialia sialis) places these sacs on electric wires, wooden fence posts, tree branches and even on top of a utility pole. Why? To reduce the chance of predators locating the nests through visual or chemical evidence.
Local birders have always been aware that certain species of birds dispose of the nestlings’ wastes via faecal sacs. The image above shows a female Scarlet-backed Flowerpecker (Dicaeum cruentatum) removing a faecal sac full of mistletoe seeds from a nestling. We take for granted that these sacs are disposed of some distance from the nests. But we should keep a look out on exactly where these sacs are disposed.

In November 2004, Tang Hung Bun observed an off-season nesting by a pair of Scarlet-backed Flowerpeckers. He videoed the feeding and removal of the faecal sac which was extra large. This large sac contained green, undigested mistletoe seeds.

Input by YC, images by YC (top, middle) and Tang Hung Bun (bottom).

Link to video provided by Tang here and another videoed by Prof Ng Soon Chye here.

One evening I found a package in my mailbox, left there by Meng and Melinda Chan. The pair was returning home from photographing a pair of nesting Red-crowned Barbet (Megalaima rafflesii) and left me the messy collection of partially digested fruits. Apparently Melinda collected them from the road nearby after the parent birds cleaned out their nest and dumped the trash some distance away.

The collection of fruits was fascinating. A few of the fruits had their bluish outer skin intact. Others were without the skin, the pulp greenish. There were a few other fruits/seeds as well, all covered with a dark, sticky and messy substance, probably originating from the rear end of the nestlings.

The bluish fruits still had a distinctive aromatic smell, reminiscence of some fruits or other that I cannot recollect. My first thought was Elaeocarpus or oil-fruit trees. These small to fairly large trees are common in our secondary forests. Their fruits ripen blue-green or blue-grey. The greenish pulp also pointed to this plant.

I checked with Ali Ibrahim who gave me some leads. Lauraceae or Elaeocarpaceae he suggested. The first includes wild cinnamon (Cinnamomum iners) while the second the oil-fruit trees, Elaeocarpus spp. The aromatic smell of the fruits suggested that it could not be the first. Cleaning the fruits and cutting it into two showed a very hard stone enclosing two seeds, each with its own cavity. Bingo! Elaeocarpus it is.
So these barbets eat Elaeocarpus fruits. They were brought to the nest and fed to the nestlings in twos and threes. Apparently the nestlings could not handle these fruits and most were probably regurgitated and deposited in the nest cavity. The parent birds had a hard time cleaning out the nest, literally carrying out these partially digested fruits in their beaks and dumping them onto the road nearby.

It has been reported that the nestlings of barbets dispose of their wastes through faecal sacs. Apparently these fruits/seeds were too large to be contained in such sacs, making it necessary for the parent birds to “shovel” them with their beaks.

Thank you Meng and Melinda Chan for collecting the fruits and for the image of the Barbet, and to Ali Ibrahim for help in the ID. Image of fruits by YC.