Avian biodiversity reaches its most spectacular levels in forested habitats at tropical latitudes. Often perceived as climatically benign and among the least challenging of habitats for birds to occupy (compared, for example, to deserts), life in tropical and subtropical forests can in fact be physiologically demanding. High air temperatures combined with oppressive humidity create stifling conditions, as anyone who has tramped through the forests of northern KwaZulu-Natal in 38-degree heat on a humid day can confirm. For birds living in open habitats along forest edges, these conditions are often combined with intense solar radiation while foraging.
The physiological challenges of very hot, humid weather arise from the fact that in these conditions birds effectively lose their primary defence against heat stress: evaporative heat evaporatively cooling. Dissipating through behaviours such as panting can take place only if the surrounding air is dry enough to absorb water vapour expelled by the bird. During periods of very high humidity, the gradient required for birds to offload heat is no longer there. Instead, the heat produced by activity or gained from the environment is retained in the birds' tissues, causing the body temperature to increase.
Denne historien er fra November/December 2022-utgaven av African Birdlife.
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Denne historien er fra November/December 2022-utgaven av African Birdlife.
Start din 7-dagers gratis prøveperiode på Magzter GOLD for å få tilgang til tusenvis av utvalgte premiumhistorier og 9000+ magasiner og aviser.
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EXPLORING NEW HORIZONS
Keith Barnes, co-author of the new Field Guide to Birds of Greater Southern Africa, chats about the long-neglected birding regions just north of the Kunene and Zambezi, getting back to watching birds and the vulture that changed his life.
footloose IN FYNBOS
The Walker Bay Diversity Trail is a leisurely hike with a multitude of flowers, feathers and flavours along the way.
Living forwards
How photographing birds helps me face adversity
CAPE crusade
The Cape Bird Club/City of Cape Town Birding Big Year Challenge
water & WINGS
WATER IS LIFE. As wildlife photographer Greg du Toit knows better than most.
winter wanderer
as summer becomes a memory in the south, the skies are a little quieter as the migrants have returned to the warming north. But one bird endemic to the southern African region takes its own little winter journey.
when perfect isn't enough
Egg signatures and forgeries in the cuckoo-drongo arms race
Southern SIGHTINGS
The late summer period naturally started quietening down after the midsummer excitement, but there were still some classy rarities on offer for birders all over the subregion. As always, none of the records included here have been adjudicated by any of the subregion's Rarities Committees.
flood impact on wetland birds
One of the features of a warming planet is increasingly erratic rainfall; years of drought followed by devastating floods. Fortunately, many waterbirds are pre-adapted to cope with such extremes, especially in southern Africa where they have evolved to exploit episodic rainfall events in semi-arid and arid regions. But how do waterbirds respond to floods in areas where rainfall - and access to water - is more predictable? Peter Ryan explores the consequences of recent floods on the birds of the Western Cape's Olifants River valley.
a star is born
It’s every producer’s dream to plan a wildlife television series and pick the right characters before filming.
