Thursday, 25 April 2019

Bad choices and bad neighbours

Air Hitam Dalam is a designated Educational Forest at Sungai Dua on mainland Penang located on the the edge of the Perai River. This park is a rather scruffy remnant of trees and mangroves that punches above its weight in terms of species observed there. One of the reasons for the diversity of species is that it is on a migration route and many interesting species drop in on their North/South travel.

The location of Air Hitam Dalam (red spot)

A bund, running north/south essentially runs parallel to the river while the rising sun comes through the trees from the east.

The bund at Air Hitam Dalam

There are resident kingfishers; Collared, White-throated and Stork-billed as well as seasonal Common and Ruddy Kingfishers. There are several groups of monkeys including Long-tailed Macaques and a strange but small group of Dusky Langurs together with a Silvered Langur or two and these two species interbreed.

Collared Kingfisher

Ruddy Kingfisher

Stork-billed Kingfisher

Young Long-tailed Macaques

Dusky Langur

Colourful species include; Blue-winged Pittas, Mangrove-Blue Flycatchers, Lineated Barbets, Flameback Woodpeckers, Yellow-rumped Flycatchers and the occasional Blue-throated Bee-eaters. 

Blue-winged Pitta

Flameback Woodpeckers (male and female)

Blue-throated Bee-eater
Coppersmith Barbet

Lineated Barbet
Black-naped Oriole

Mangrove Blue Flycatcher

Yellow-rumped Flycatcher (male)

Yellow-vented Bulbuls and Yellow-bellied Prinias welcome the morning sun while Asian Open-billed storks leave their night-time roosts and head for the rice fields. Raptors are represented by Brahminy Kites, Black Kites and Crested Serpent eagles. 

Roosting Asian Open-billed storks

Asian Openbills

Yellow-bellied Prinia

Brahminy Kite (above) with a Black Kite
Crested Serpent Eagle

Migrants include Indian Cuckoos, Brown Shrikes and Asian Paradise Flycatchers. 

Brown Shrike

Indian Cuckoo

I have recorded three species of owls over the years; Barn Owls, Buffy Fish Owls and Spotted Wood owls. 

Barn Owl

Buffy Fish Owl

Spotted Wood Owl

This story is about the pair of Spotted Wood Owls that have been seen for the last 5 breeding seasons. This is the story of the 2019 season.
Below is the fact sheet and world distribution of Spotted Wood Owls.

Distribution of Spotted Wood Owls

In previous seasons the pair of owls could be seen sitting high up in a large tree. I wondered a number of times where their nest hole could be. Nobody else seemed to know either. I made weekly trips to the forest early in 2019. I had seen a potential hole that was well illuminated by the morning sun. 

Tree cavity
From a photographic perspective the potential nest hole (centre of the image below) was well illuminated in the early morning but with a limited window. I used 700mm of lens mounted on a sturdy tripod. The limited view gave little warning of  potential action around the hole.

On one visit in March I saw a large bird at the hole looking agitated. I initially thought it was a Crested Serpent Eagle until it was identified as a spotted wood owl. I saw the reason for its was trying to shift a large Clouded Monitor Lizard from its nest cavity. As soon as the lizard exposed itself it was repeatedly attacked by the owls in a coordinated manner. I assumed the lizard was raiding the owls eggs.

The following three images showing a strafing attack consist of one sequence at 1/10 second intervals. My shooting window through the tree cover was not very large. 

The culprit is now clearly seen.

A second flyby.

The main mission of my next visit the following week was to see if the owls had recovered from the robbery and had resumed normal nesting activities. For the next three weekly visits the female owl was present in the nest.  

On the next visit the female was not in the nest but I located her in the tree above the nesting cavity. I was hoping to get a shot of her arriving at the nest.

Over 30 days had elapsed since the previous lizard raid.....just enough time for chicks to emerge if eggs were laid soon after the attack. I was a bit surprised after half an hour to see the lizard tail emerge again from the cavity which immediately activated both owls to attack. The attacks were well coordinated, and the lizard was driven off. I thought I could see another tail tip still protruding from the cavity, indicating that there was two raiders.

The initial attack

A double Owl attack

The lizard decides to leave

....and exposes itself to another attack
Monitor Lizards are large lizards in the genus Varanus. They are native to Africa, Asia and Oceania, but are also found in the Americas as an invasive species. A total of 79 species are currently recognized, the Komodo Dragon being the largest. Monitor lizards have long necks, powerful tails and claws, and well-developed limbs. They are seen wrestling in disputes over food, females or territory.

Malaysian Water Monitor

Malaysian Water Monitor

Wrestling bouts are not uncommon

Clouded Monitor lizards are adept at climbing trees

There are two species of monitor lizards commonly seen in Malaysia.....Water Monitors and Clouded Monitors. The former, as their name suggests is seen in rivers and in and around seasides. Clouded Monitors are good tree climbers and generally slightly smaller than their aquatic cousins. The nostrils of the water Monitors are located slightly closer to the snout. 

A week later there was no owl on the nest, but I located the female further up the tree. She made no attempt to return to the cavity. I then noticed something further down the tree that  indicated how the lizards located the owl nest even when recognising they sense with a forked tongue. Two lizards were in and around another cavity. Thus the pair of Clouded Monitors had a ‘home-base’ in the same tree as the owl nest.

A week later there was one lizard seen initially in the hole and later was observed sunning itself on the side of the tree.

The respective locations of the two nest cavities; Red arrow = owl nest, yellow arrow = monitor home.

A week later there were no sign of the owls or lizards.

My summation of the whole event was that the owls started nesting normally but chose an ‘apartment’ in the wrong ‘high-rise building’. The owls were not going to have the same scenario again so moved somewhere else. It is a pity because we may not see them back in the same location again.

1 comment:

  1. Great photos.
    I recently dug a pond, and almost immediately white throated Kingfishers started digging a nest. We left the site relatively undisturbed, but they seem to have abandoned after about a month. I have not been watching them closely, at least not until they are settled. Interestingly, lapwings have been noisy on the other side of the surrounding wall. I notice your reference to them being not so compatible. Do they abandon nests easily. I should take a closer look, and maybe check inside, but I hear them around, and get glimpses, but not near the nest.