Friday 29 August 2014

A kill on the wing!



On a recent trip to the Kruger National Park, we parked on the high level bridge over the Shingwedzi River, enjoying the amazing sunset. A ranger mate who used to be stationed at Shingwedzi always assured me that Bat Hawks did indeed exist, as he had seen them in the area from time to time. “Yeah, right...” was my usual reply!

So there we were, clicking away with our cameras, whilst keeping an eye on the bats emerging from their roost under the bridge, when two dark birds swooped over the river from some nearby large trees. Could these be the elusive Bat Hawks I have wanted to see for years? Binoculars quickly replaced the camera and my eyes confirmed the over-excited expletives from my husband – our first sighting of a Bat Hawk!

Image: Bat Hawk in daylight by Johan Janse van Rensburg
The Bat Hawks started their hunt as one swooped on a bat. 

The bat detected the threat and swiftly took impressive evasive action, only to fly directly into the path of the second Bat Hawk – we had just witnessed a ‘kill on the wing’. 

It all happened very quickly and, with the light fading and gate-closing-time fast approaching, I did not manage to get photographic evidence of this incredible sight, but I definitely have a picture in my mind that I will never forget.

Back at camp, the reference books came out and we read that Bat Hawks do indeed hunt their prey on the wing, catching prey with their feet and - if the prey item is small enough - swallowing it whole in flight. 

Insectivorous bats are the usual prey of the Bat Hawk, with most hunting occurring at dusk. The bird can catch its daily food requirement within only twenty to thirty minutes. 

It is estimated that there are no more than five breeding pairs of Bat Hawks in the Kruger National Park[1] and they haveNear-threatened’ status in SA - so this is a very rare bird to see.

Image: Shingwedzi sunset by Jenny Bell
We returned to the bridge the following evening and - luckily - the Bat Hawks made another appearance at sunset...so keep an eye out for them next time you overnight at Shingwedzi!

The ANT Blog 
- written by Nature Enthusiast Course student, Jenny Bell


[1] http://www.birdlife.org.za/conservation/important-bird-areas/iba-directory/item/143-sa002-kruger-national-park

Friday 15 August 2014

Have you noticed that the full moon has recently got bigger?

No, it has not really got bigger at all – the Moon’s orbit has just been a bit closer than normal to our planet the past month or so and this has resulted in the moon appearing to be bigger and brighter.

Image: Eric Goody
This interesting phenomenon is referred to as a ‘Supermoon’ and it occurs when the proximity of the Moon to the Earth accompanies the full moon phase of the Moon’s cycle.

2014 will be a bit of a record with Supermoons, with three occurring in one year: the first two in July and August and the final Supermoon in September. To have three Supermoons in such close succession is rare and is not expected to happen again until 2034!

It is not only during Supermoons that the moon appears larger. Have you observed that a full moon rising appears to be larger than compared to when the full moon is directly overhead?

The moon doesn’t physically change size over the course of an evening , so why does our brain think it has?

This phenomenon illustrates the Ebbinghaus Illusion. When the Moon rises and is visible on the horizon, the human eye compares its size to other visible objects (trees, power lines, buildings, etc) and, versus these objects, the Moon appears comparatively much larger. However, once the moon rises higher in the night sky, the human eye has no other objects against which to compare the moon’s size and it then appears comparatively smaller.

http://www.universetoday.com/83998/the-supermoon-illusion/
 In this image, the two orange circles are exactly the same size, but we perceive them as being different, which demonstrates the Ebbinghaus Illusion.

So our mind plays tricks on us, making us think that the size of the full moon changes during the course of an evening!

Think about this as you enjoy the next Supermoon on September 9th and please share your images on this blog...


The ANT Blog