Monday, 7 September 2015

Birds and Light - On Grassland

When we think of grasslands we probably consider the prairies of North America, the llanos and pampas of South America, the steppes of Asia, the veld or savanna of Africa or the downlands of Australia.  But add to that all the cultivated areas of the planet and even the tundra and semiarid areas and it's pretty clear this wide, expansive type of habitat dominates the landscape of most countries.

Of course the most recognisable feature of grassland is it's habit of frustrating the observer.  This time the quarry is a Least Seedsnipe (Thinocorus rumicivorus), photographed in Chile.

Where natural grasslands occur on the planet they are not always so green and lush.  Seasonal rain brings new growth which supports the breeding cycle of many herbivores and associated ecosystems.  But in many parts of the planet this is followed by much drier conditions and very often fire and regeneration of the grassland habitat.  But lets start with the lush green growth that we certainly associate with grasslands here in Ireland.  There are two photographic factors to consider.

Firstly fresh green grass transmits and reflects a considerable amount of green light.   This may not dominate a scene quite as well as it does under foliage canopy.  Nevertheless it can have some impact, particularly on underparts colouration.  Secondly a dominance of a single colour in any image can confuse a camera's auto white balance function.  So, it is not unusual for photographs containing a lot of green grass to have an unnatural white balance tilt along the green-magenta axis.  As discussed under an earlier posting HERE this problem can only be corrected using a proper white balance tool.  Some white balance or colour temperature tools only correct along the yellow-blue colour axis and don't allow for the correct white balancing of these types of images.

This Sedge Warbler (Acrocephalus schoenobaenus) against a dominant green background will tend towards a green white balance error, requiring some careful white balance correction.  Unlike its much skulkier cousin the Aquatic Warbler (Acrocephalus paludicola) Sedge will often show quite well with a bit of patience, particularly during spring migration, when this image was taken.

Browns, Yellows and Greys
Many grassland birds tend to be brown and streaky.  Very often quite similar species occur together in the same area thanks to the rich availability of ecological niches in natural grasslands.  

Bland, desaturated colours like pale browns and greys are more susceptible to lighting issues than bold colours as discussed HERE.  Take for example the Golden Plover image below.  Within this flock of European Golden Plover (Pluvialis apricaria) there are two Americans (Pluvialis dominica).  The predominantly blue light before sunrise and after sunset, the yellow light of dawn and dusk, the dull grey light of an overcast day and the harsh light at high noon are all challenging lighting conditions for picking out subtle differences like the generally colder plumage of a juvenile AGP in a flock of EGPs.

Grass grows very well in temperate climates due to the high rainfall, reasonable temperatures and adequate sunlight, but if left to nature deciduous and mixed forest will regain dominance.  Where natural grasslands dominate lush green growth is not the norm and for much of the year the grass is yellow and stunted.

Despite it's large size a Double-striped Thick-knee (Burhinus bistriatus) can be feet away and yet perfectly blended with this dry llanos in Venezuela.  In the warm late evening light the camouflage is no less striking.

Heat Haze
Natural grasslands tend to be hot places.  They also often tend to be quite flat and featureless.  Not only are grassland birds hidden in the long, dense grass much of the time, but it is difficult to approach birds in this habitat.  So inevitably we resort to watching and photographing grassland birds at longer range than we might like.  This can be a truly frustrating form of birding!  Heat haze as we know gets worse with distance so this very challenging natural image artefact is at work during many grassland observations.  Really the best time to be out grassland birding is in the early morning or late afternoon, when temperatures are lower and birds are more active. 

Heat haze frustrates photography in the Ethiopian Highlands where this Abyssinian Longclaw (Macronyx flavicollis) demonstrates that interesting convergent evolution between the Longclaws of Africa and Meadowlarks of the Americas.

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