Nesting/Feeding of Chicks of Common Tailorbird (Orthotomus sutorius maculicollis)

Disclosure
“We are careful with nesting birds and limit contact/close observations. In this case the nest was in our home and partially visible from our kitchen window. In addition we often needed to walk just next to it for basic household activities. We observed this nest frequently from inside the home (tinted windows) and intermittently as we walked by. On two occasions I put up a video recording using the Nikon P900 in the garden, and left it recording unattended. The nest was hard to image as our garden is overgrown with many shrubs and small trees. I used some limited handheld photography with a long lens (600mm x 1.5 DX format), with no flash, primarily at the time of fledging. We monitored their behaviour and they did not appear distressed by our presence. Parents would even feed juveniles in our presence when we walked past the nest, less than 1 meter away.

Overview of Observations
“We had another opportunity to watch Common Tailorbirds nesting in our garden. True to form they made many calls at one location in the garden to keep us focused while they silently built the nest at another site. On this occasion they used a young fig tree, planted by one of our garden birds, that is growing outside our kitchen window. We spotted the nest just as it was being completed. The nest was located around 2.7 meters up. Although originally built horizontally, it took a full vertical orientation once eggs were laid and incubation began (below). The proximity of the nest allowed for some close observation of feeding behaviour, the primary focus of this field note.

One odd behaviour observed during nest building was the male fluttering his wings to the female; very much like juveniles begging for food (below). This happened 4 days before hatching and I suspect it is some form of courtship behaviour.

“Nest building was conducted by both partners.

Timelines for Nesting
“1. 24th May 2016 – eggs laid and incubation started, unsure if all were laid on the same day and unsure of size of clutch. The incubation was done almost exclusively by the female with very few changeovers with the male. Incubation period was 13 days.

“2. 7th June 2016 – hatched, started feeding, unsure if all hatched on the same day. Fledgling period was 12 days.

“3. 19th June 2016 fledged – there were 3 fledglings on the same morning but one came out a few hours later than the first 2.

Feeding Observations
“Feeding occurred frequently from the time of hatching right into fledging. There were periods when the frequency was high, early mornings and late evenings. But there were lulls in between, especially in the heat of the day or when parents were feeding themselves. Prey brought to the nest were not easy to identify as the activity is rapid but video recording and playback helped greatly. Male and female parents could be identified by tail structure. Generally feeding commenced in early juvenile stage with softer invertebrates, then smaller insects, and progressed to larger insects. No vegetable or fruit material was seen offered to juveniles. We have been routinely observing insect life in our garden and notice that this family of Tailorbirds has had an enormous impact on the volume of insects in our wild urban garden. For example most of our Leaf Hopper (Bothrogonia ferruginea) that usually numbered in the 50-70s were almost completely wiped out; as were the majority of the small moths that rest under leaves (ID yet to be determined) and many caterpillars. Parents foraged almost exclusively from our rich garden until the fledging period. By this time they fledged, the insect volume had become limited and they moved their brood on Day 3 post fledging to a nearby overgrown Chinese cemetery. We have since seen the older juveniles return for a bite in the garden.

“From a 105 minute consecutive video observation taken in the morning on day 8 after hatching, 21 consecutive feeding episodes were recorded:

“1. 10 feeds were by the female and 11 by male. My initial impression was that the female fed more often and the male brought more diverse prey. But this was not borne out by video recording.

“2. Male and female parents generally feed at different times but were once documented feeding together.

“3. All the prey were invertebrates or insects. 12 of the prey were moths (wings fed with body), 4 caterpillars, 2 worms, 1 praying mantis, 1 winged insect and one unknown small item.

“4. For the 105 minutes (1.75 hours) consecutive observations the mean feeding frequency (time between consecutive feeds) was 182 seconds (3.03 minutes), Standard Deviation 128 seconds (2.13 minutes), minimum to maximum duration 8 to 452 seconds (0.13 to 7.53 minutes); 50% of feeds were within 159 seconds (2.65 minutes) of each other. More details are in the table below.

“5. The figure below shows a box-plot of feeding frequency by female and male. There is no significant difference in feeding frequency (p < 0.05).

“6. Adults used the lip of the nest to perch while feeding chicks. But at this point the chicks were large enough to rear their head up and could take feeds by reaching ‘outside’.

“7. There were 2 faecal sac removals during the 105 minute period. Both parents removed faecal sacs. I presume the frequency of faecal sac removal will be based on food availability/feeding frequency
(below).

[Video grab image of faecal sac removal by female (left) and male (right) after feeding]

“An edited video of the 105 minutes, trimmed to 7 minutes 30 seconds to display all 21 feeding episodes, the faecal sac removals and some chick movements can be found below:

Additional Observations on Feeding
“1. There were no calls by the chicks during any feeding episodes while in the nest or even after fledging. The only vocalisation I head from chicks is when they had fledged and were badly drenched and hungry in the cold rain (recording available). They also seem to ignore all the other birds chirping around the nest.

“2. The parents were silent when approaching the nest and only made calls if there was some perceived danger (my tripod & camera).

“3. Once a particular food source was found, the adults often gave the same prey in rapid succession. For example, one late evening, after a bad storm, the chicks were fed 6 flying termites in a row.

Fledging and Progress of Juveniles
“1. Three chicks fledged on 19th June 2016, 12 days after hatching. Two left the nest early and one came out a few hours later (below).

“2. The day of fledgling was very opportune, as that evening there was a violent storm and the young fig tree was completely bowed over. The branch on which the nest was built was only 0.75 meters from the ground. We suspect the chicks would have died in the upheaval.

“3. The parents gradually moved the chicks over the next three days to various parts of our garden to enable feeding, using calls as a means to direct them.

“4. On day 3 post-fledging the parents moved the fledglings to an adjacent overgrown Chinese cemetery, primarily as our garden insect volume had been depleted. Juveniles have been seen visiting the garden to feed recently.

[Common Tailorbird fledglings in the garden (Day 1-Day3)]

Nest Structure
“As the nesting branch was damaged by the storm and no longer in use, we decided to remove the nest for observation after day 3 of fledgling. The nest proper was 10.0 cm long, with a width of 5.5 cm and a circumference of 20.0 cm. Of the 10.0 cm nest length 5.5 cm is padding and only 4.5 cm a cavity (below).

“The inside of the nest (cavity) is heavily plugged with ‘cotton’ padding and fibre, as is the base of the nest (below). The cavity opening is 4.5 x 4.5cm.

“The nest is still available for any queries.”

Dato’ Dr Amar-Singh HSS
Ipoh, Perak, Malaysia
May-June 2016