Sunday, April 26, 2020

The mysterious nightjar of Maliau Basin

The Maliau nightjar has come back to haunt the bird photography fraternity during this Covid-19 Movement Control Order (MCO) period, as the MCO makes all bird photographers to stay at home digging their harddrives for bird images to post.

The said nightjar was claimed to be Bornaparte's by many, myself included. Now it is ID not Bornaparte's from images posted in FaceBook (FB).

It is too lengthy to post what I am going to say in FB, so I post it here and link this  to FB for those who are interested to see what I have to say.

The purpose of this post is to provide more information which might not be available from the single image seen in FB, I hope these additional information might help us to nail the true identity of the nightjar.

I first photographed the nightjar with my bird photography group in the evening of 30 August 2014 5.47 pm, again on the next day, also on 11 and 12 October 2014. I photographed a nightjar around the vicinity (the area where we photographed the first bird had been bulldozed to make sealed all-weather road subsequently) on 21 June 2019, this bird looks very similar to the earlier bird.


The 2014 bird should be the same individual, whereas the 2019 bird was another younger individual as its beck  not as massive, upper mandible did not project as long over the lower mandible, see image below. 

We are seeing two individuals with remarkable similar wing coverts patterns, 5 years apart.

Now, what nightjar is it actually?

Borneo has 5 recorded nightjar species, they are 
  1. Malaysian Eared Nightjar [25-28 cm], 
  2. Grey Nightjar [28-32 cm], and 
  3. Large-tailed Nightjar [25-29 cm],
  4. Savanna Nightjar [20-26 cm], and
  5. Bornaparte's Nightjar [21-22 cm].
Since we were not sure what it was, we did the obvious, we would eliminate all the unlikely candidates, the one that remained should be it. 

Let me summarize the habitat, the bird size and call before the elimination.

The 2014 bird was about 18-20 cm (about Asian Glossy Starling size) at most and the 2019 bird was smaller, about 15-16 cm. Size estimated visually not by actual measurement. 

Habitat was barren hill slope that remained after cutting for road making, see image below. The bird was nesting there in August 2014, a single egg was seen on the ground.

No call was heard on all occasions.

First we eliminated Malaysian Eared, and Large-tailed, on size and obvious differences. 

Grey was also out because it is a wintering migrant here and the size didn't match. Grey was never revisited subsequently because of the following image.

Savanna fitted the size but was also ruled out as it was not recorded in Sabah, the Maliau bird looked different anyway.

What remained was Bornaparte's, and we took it as Bornaparte's and we agreed not to publicize the bird nor the location as it was nesting there,  it was thus not widely known.

Now it is established that it's wing coverts conform to Grey rather than Bornaparte's, and its identification as a Grey Nightjar is also concurred by regional bird experts in the following FB pages, here


However, I am of the view that the Maliau bird is not a migratory Grey Nightjar Caprimulgus jotaka jotaka due to the following reasons:

1. Grey Nightjar is a big bird measuring 28-32 cm, a bird of that size will be hard to mis-measure visually, the Maliau bird is much smaller. The 2014 August nesting bird which evidently was of adult age definitely did not measure one foot in length. It is an established fact that the Maliau Nightjar is of small size, all observers and photographers who have seen it can testify to it's size.

2. Maliau Bird was in an active nest, it was a breeding resident, and

3. A similar, obviously younger bird was there in June 2019, well outside the normal migratory season.

Now all recorded Nightjar species in Sabah have been eliminated, but before we conclude, let us relook at Savanna Nightjar again, the most probable bird in term of size. 

Savanna Nightjar occurs only in Kalimantan in Borneo. There are some images of Kalimantan birds in HBW website here

https://www.hbw.com/ibc/species/55231/photos

Most birds there are generally paler, but I notice that every bird there look very different individually, though they are all Savanna.

Our two Maliau Birds, on the other hand, look surprisingly similar to each other.

Is it an unrecorded race of Savanna or a new undescribed nightjar from Sabah?

More need to be done, and for a start, those who have access to the area please try to record its call.

It will be very interesting after the MCO.

Cheers and happy birding. 


Edited on 27 April 2020 to add the following comments in FB on 26 April 2020 for the benefit of readers:

James Eaton commented: 
Hi Wong, could I ask, why are these chestnut-eared birds not female Large-tailed Nightjars?
Regarding the size, female Large-tailed will be smaller than the male, and is only a little larger than Bonaparte's (and smaller than Grey).
It has chestnut ea
r-coverts. The tail is very long too in that cover photo - way beyond the wing tips.

When it's nesting, it's likely to ruffle the wing feathers to make itself look less bird-shaped, so the classic pale lines in the wing of Large-tailed would be less obvious.

For an example of a female Large-tailed, see here:
https://macaulaylibrary.org/asset/23285621
Dave Bakewell commented:
I'd agree. Earlier I mistakenly identified your pic on BBI as a Grey Nightjar Wong Tsu Shi. Looking at these images with more care, I think the wing convert pattern and ear covert colour are wrong for that species and right for Large-tailed.

I commented:
According to Smythis (1999), which I quote "The bristles at the gape are said to be all black in the Grey Nightjar, but white at base in the Long-tailed."

In The Birds of the Malay Peninsula Vol. 1 (1927), page 117, under Adult female Large-tailed Nig
htjar, I quote "rictal bristles white at the base".

In The Birds of the Malay Peninsula Vol. 4 (1939), page 103, I quote "In both sexes the rictal bristles are black with white bases."

James Eaton links an image that shows the rictal bristles clearly as described in these three volumes.

A good number of images in Oriental Bird Images clearly show the white-based black bristles as well.
Both the Maliau Nightjars have entirely black rictal bristles.

James Eaton commented: 

thanks for the details, Wong, very minute details! On the close images, such as the bird that is wet, facing left, you can see the white base to the rictal bristles. For the bird from 21 June, facing right, you can also see the white base to some of the rictal bristles there too.

It is also worth noting it is a different race to the birds from the Peninsular, which are more striking in plumage. Large-tailed on Borneo is darker, blacker above, and seemingly less conspicuous wing patterning looking at photos online.


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