Saturday, 22 November 2014

Birds and Light - Arid and Semiarid Areas

Light and Shade in Arid and Semiarid Areas 

Characterised by low rainfall levels, sparse vegetation and high temperatures, arid and semiarid areas  are among the most extreme environments for life, and one of the most challenging environments for birding and photography.  Birds in arid and semiarid areas tend to be nomadic, which adds to the challenge and reward of desert birding.

Desert Sparrow Passer simplex (Morocco) is typical of many desert species.  It's field marks are subdued and colours subtle, which makes it a difficult species to photograph properly.  Changing lighting and shadows have a more dramatic effect on subtle plumage tones.  Harsh light, particularly extreme ultraviolet light damages feathers and bleaches out pigments.  Water loss is greater due to higher temperatures.  Insects and other animals are also consequently harder to find during the heat of the day.  Not surprisingly, most desert birds try to keep out of direct midday sun.  On the rare occasion that I have seen small passerines asleep during the day, it tended to be in arid environments.   Only mad dogs and birders risk life and limb being out during the intense heat of the day (as I have painfully learnt).  The other big issue of course with birding in the desert is heat haze, which can begin to manifest very soon after the sun comes up.

The main characteristics of lighting in arid and semiarid areas are as follows:-  

High Contrast
Midday sun is high in contrast,  While birds are much harder to find at this time of the day, it doesn't stop birders looking for them.  Images captured under these conditions often have high dynamic range, with burnt out mid-tones.  Heat haze can also affect image sharpness.

Male Moussier's Redstart Phoenicurus moussieri, Morocco.  

While most desert birds are subtle in appearance there are also desert and semiarid species which exhibit high contrast plumage markings.  Is this related to the high lighting contrast typical of these areas?   Note the strong wear on the wings and tail of this male, photographed in mid-April as the first clutches are about to hatch.

Colour Balance
Because birds tend to be most active in arid and semiarid areas around dawn and dusk, this is often the time when photographic opportunities present themselves.  The low position of the sun in the sky adds a yellow to reddish tone to images.  This can be further enhanced by the natural tones of soil, sand and rocks.  Birds also tend to be active during twilight hours when the lighting is strongly blue in tone.  This colour can be either enhanced or possibly even masked by the surrounding terrain (making it hard to detect in photographs).  When we are reliant on white balance for accurately gauging subtle plumage tones, these lighting conditions can present a big problem.

'Desert' Olivaceous Warbler Iduna pallida reiseri, Morocco (slighly defocused & overexposed).

Identification of Iduna species (formerly the pale brown Hippolais warblers) is very tricky.  'Desert' Olivaceous Warbler, as the name suggests, is confined to the more arid areas of North Africa.  They differ from the more widespread Isabelline (alternatively Western Olivaceous) Warbler Iduna opaca in having a shorter, narrower bill, and possibly based on some very subtle plumage colouration, such as generally warmer-looking ear-coverts, lores and rear flanks.  Identification of a putative reiseri requires good low-contrast light with minimal external colour influences.  Mid-morning might be the best time to be looking for one!  

Dull Light
Dull light is usually only an issue in the desert around twilight, or on the rare occasion that rain or a sand storm threatens.  This creates monochromatic lighting conditions.   For many arid and semiarid species which have subtle plumage tones, this simply means they blend in even more with their surroundings.  Identification of a great many desert species relies on subtle judgements of plumage markings, size and structural features.

Crested Lark Galerida cristata, Morocco.

Few species pairs are as difficult to separate as Crested (G. cristata) and Thekla (G, theklae) Larks.  With a multitude of races, identification comes down to subtle shape, plumage markings and some subtle plumage colours.  Once again, good lighting is key!

Ultraviolet Light
Ultraviolet is invisible to humans but many birds can see well in UV.  Digital camera sensors are naturally sensitive to UV so camera equipment which lacks or has poor UV filtration (eg. some digital camcorders) can produce images with unnatural colours.  UV can be really intense in desert areas so this is something to consider.  Most modern digital cameras including most DSLRs have good UV filtration to prevent this normally unwanted light from reaching the sensor.  Note however that some Nikon cameras do not have good UV filtration so perhaps might be more prone to this problem.  For more on UV see HERE.

Looking for Larks, Pipits and Wheatears beside the Tagdilt Track, Morocco, mid-April, 2006.  Not a great year for some of the more nomadic species but still plenty of jewels to be had among the rough - just adds to the spice of desert birding!  Note the presence of a high level of UV can manifest in the form of a hazy looking backdrop.  An additional UV filter may boost contrast slightly and remove some of this haze.  However, in the desert most of the haze is probably being caused by dust, not by UV.  More on filters HERE.  Find your UV exposure risk HERE.

Temminck's Lark Eremophila bilopha, Tagdilt Track, Morocco

Seebohm's Wheatear Oenanthe seebohmi,  Tagdilt Track, Morocco.  Recently split from Northern Wheatear O. oenanthe.

All images were taken with a Kyocera Contax U4R.  Bird images were all digiscoped with the aid of a Leica Televid 77 scope and zoom eyepiece set to 20X.

No comments:

Post a Comment