Bat Hawk – nictitating membrane

posted in: birds, eyes, Raptors | 0

Post 1.

This was a totally unexpected find this morning in our neighbourhood. We had just return from cycling when my wife spotted the Bat Hawk (Macheiramphus alcinus alcinus) in our neighbourhood raptor-snagging-tree. It was unexpected as it was already 7.50am. I have seen these birds at the outskirts of the city, near limestone hills, but usually an early morning fly by. Unfortunately, no flight images but still a great treat to see it in some light.

Post 2.

The bird was harassed by one of our local Dollarbird (Eurystomus orientalis) that uses this perch. It made 6 fast swops with harsh cries to try and dislodge the raptor. But was sadly ignored and the Dollarbird left.

Post 3.

Of interest was that the Bat Hawk used its nictitating membranes much of the time (many images) to cover the eyes. I wondered whether the strong morning light was disturbing it? Or that was planning to roost there and this was a sleep behaviour? The nictitating membranes looked unusually thick and white, and looked almost opaque as in some owls. Some images of the of this membrane looked ghostly.

I had a busy day with errands and so had to limit observations, but noted that the bird had left by 8.25am.

Post 4.

A video made in an earlier encounter on 20th March 2018 (post 4) using Nikon P900 when the bird was perched at 7.30am (dark, overcast morning) can be viewed here: https://youtu.be/X6KHjtRswyo. Itl constantly looked around, possibly for prey; did not attack passing swifts. Some preening in video. No calls heard.

 

Amar-Singh HSS (Dato’ Dr) – Ipoh, Perak, Malaysia

Habitat: Urban city environment

Date: 18th November 2018

Equipment: Nikon D500 SLR with Tamron SP 150-600mm f/5-6.3 Di VC USD, handheld

 

Discussions

Hans Peeters of California, USA has this to say:

What a wonderful sighting! Good pictures of Bat Hawks are few and far between. The opaque eye covering, where present in these photos, is actually the lower eyelid: in the third picture of this post, you can actually see a part of the eye above the rim of the lid. As in other raptors, the eyelids are covered with a velvety nap, often white, but light grey in this species, as is, incidentally, the supraorbital shelf (which however is unfeathered). The actual nictitating membrane is inserted anterior to the eye.

Fine images. I tried hard to get a good look at them in Borneo but my photos don’t even approach the quality of your shots. By the way, we saw them catch a number of bats quite easily, and eat them whole in the air; but I would love to see them as close as you did.

Amar’s response:

Appreciate the information on eyelids. Still wonder if it was planning to rooster there in broad daylight? and got disturbed and left. Hope to see more in good light.

According to Krys Kazmierczak:

Nictitating membrane or eyelid? Looks like eyelid to me but not sure in these pix. The eyelid closes from top down. The nictitating membrane moves from inside to out.

 

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