Black-thighed Falconets - Part lll, nestlings and diet/feeding behaviour

It was evident that these chicks were growing at different rates, the younger appeared hatched more than a couple of days later than its older siblings.

It was pretty challenging to identify each individual chick at a look except on close scrutiny and comparison.  Changes to feathers and colours were happening daily that differences were noticeable just in 2 days' time.

The differences in the chick ages were deduced from their tail feathers displayed when they turned their backs to discharge out of the nest entrance, whenever happened, and also type of feather growth on their head, belly and wings.

The chick who looked the oldest at approximately 15 days old, was already showing curiosity at the outside world.

Another chick perhaps at less than 15 days displayed a well-developed leg but a rather weak squirt that landed at the entrance edge.

The issue of how many chicks continued as comparison after comparison was made, perhaps four?

18-22 days old

Probably the youngest one.

All the chicks seen on the same day.

Only two days later, and differences in appearances namely feathers and skin colours were easily discernible.

The chicks showed amazing alertness as  now as their heads turned almost 180 degrees as their eyes followed the parents leaving the nest.

Profile of an approximately 23 days old chick.

As the chicks approached or reached their 30th day.

Meanwhile the parents maintained their routine of feeding large preys in the morning, sometimes mid-day too, and late afternoon.  And whilst providing food for their young also took portions for themselves as they tore loose in particular bird preys - probably at this stage the young were still unable to feed on the tougher meat or pick off the bones.

It's not unusual to see the chicks retain blood stains on their beaks for all those vertebrate meals.

A blood-smeared chin after a bird prey meal.

Lizards might be a frequent catch but it looked like for the chicks not all foods were equal.

Sometimes there was no telling between the parents if a catch had been made, as in this case one parent took in a bat prey to be followed almost immediately by the male parent who arrived with a Flying Lizard.

The male parent exited immediately with the lizard prey.

The lizard was taken in again after being partially torn up, to be taken out again.

It appeared that much more was needed to be done before it could be feasted on by the babies.

As soon as the torn-up lizard was taken in, the female exited with part of a bony bat wing for its own meal.

Shortly after the lizard prey was served this happened - would the new parents eventually learnt that not every part of a prey was suitable for chicks of this age?

And this one learnt the hard way too, with what looked like a remain of bat wing.

Nevertheless the chicks would constantly appear at the entrance to await their parents for food.

Feeding at the entrance occurred later with these chicks - they were almost 30 days old before it happened; before, food was taken in or simply thrown in.

Did the chicks look like they would fledge after 30 days?

They were now all over each other in the small cavity nest.

A playful moment.

A 'painful' moment - being squeezed out off its front seat position!

Again, the older sibling seemingly trying to push its way to the front with its very well-developed leg.  It hogged the entrance and only made way for the younger ones when they wanted to poop outwards.

A rare sight of an older and a younger one together, suggesting the rather vast age difference.

Blocking the entrance and grabbing the food first, it was no guess why the older one grew the fastest!

Delivering to the entrance edge and leaving right after.

As the chicks grew, preys were delivered whole.  However sometimes when the nest entrance was blocked by an impatient chick, the parent cleaned up the prey right at the entrance, in this case tearing apart the body of a dragonfly before giving it to the chick.

Holding the prey and eating like an adult.

Some observations and deductions:

1. The pair were raising their young on their own and independently.  There was no communal feeding.  Nevertheless the chicks did grow well and fast.

2.  Big preys comprised mainly small birds, lizards like garden fence lizards and flying lizards, skinks, bats and rats.  However, it was difficult to identify the bird preys as these were all de-feathered, torn up but still in one piece before taken into the nest; however on numerous occasions the preys were seen to be taken in and out at least three times to be further torn apart before finally being left inside the nest.  Nothing went to waste as bony parts like wings and legs were taken out to be eaten by the parents themselves.

3. Small preys which included mainly moths, butterflies, dragonflies and beetles were taken in whole as the chicks grew bigger with rejects of mainly wings torn off before taken in or discarded out of the nest.  These preys were typically caught within 50m radius of the nest as the parents would swoop high or low from open perches opposite the nest or close-by trees.

4. The parents seemed to have a routine of catching big preys during early morning, mid-day and late afternoon, left it inside for the chicks to feed on, and in between caught smaller preys as fillers.

5. The older the chicks got they were able to emulate the adults holding on to and eating the smaller prey while upright.  

6. Characteristically they learnt to bob their heads regularly, and opened and closed their beaks.

[AI overview:

Primary Prey

Insects: their diet heavily consists of arthropods, including cicadas, dragonflies, butterflies, bees, moths, and grasshoppers.

Vertebrates: they frequently hunt small birds, bats, and small lizards.

Hunting and Feeding BehaviorAerial Ambush: they hunt from a strategic, exposed perch and launch swift attacks. While they often catch flying insects mid-air, they can also pursue small birds in rapid aerial chases.

Perch Eating: Falconets usually return to the exact same perch to tear apart and consume their prey shortly after a successful hunt.

Communal Feeding: Some species (like the Black-thighed Falconet found in Malaysia) exhibit communal feeding habits, with up to four individuals sometimes eating from a single large prey item. This behavior may help teach younger falconets how to hunt.]

7. In view of the absence of communal feeding, it was anticipated that these chicks would take longer to fledge. 

[AI overview:

Hatchlings (Days 1-5):

Skin and Down: completely blind and helpless, hatchlings emerge with pinkish skin covered in sparse, wet white down that dries into a fluffy coat. 

Proportions: they possess oversized feet, a large head, and a short, fleshy, soft beak.

Eyes: closed tightly for the first few days.

Nestlings (Days 6-15):

Eyes and Size: eyes open completely, revealing dark, alert irises.  They grow rapidly to nearly double their hatching size.

Secondary Down: The initial down is replaced by a much thicker, denser layer of greyish-white secondary down.

Pin feathers: dark pin feathers shafts begin to push through the down along the wings, tail, and head, making them look spikey and 'thorny'.

Fledglings & Juveniles (Days 16-35):

Plumage: real feathers rapidly burst from the pin shafts.  By week four, the chicks look like miniatures of the adults with distinct colour variations.

Face and wash: their white facial patches, throat, and chests often carry a distinct buff, yellowish, or warm rufous wash.

Feather Texture: the plumage appears looser, softer, and fluffier than a sleek adult.

Bill and Cere: the plumage hardens into a dark charcoal colour, and the cere (the fleshy area above the beak) remains a pale bluish-blue.]