by Jamie Walker
By the time you read this, we will be long past the solstice, spring will be evident, and the natural world will be enlivened by lengthened daylight and increasing warmth.
The ambient temperatures of different latitudes impact enormously on ecological variety. For every 20 species of insects found in Tasmania, there are 200 in the Daintree.
Cold climate animals can be huge compared to those found in the tropics, because the bigger you are, the smaller is the ratio of your surface area to your body’s mass; and it is through your skin that you may lose precious body heat.
So, a Polar Bear is five times the size of a Malayan Sun Bear, and Tasmanian Forester Kangaroos (which must cope with snow) are larger than our Eastern Greys.
In Australia, the sun can be dangerously punishing, but it is still nature’s consistent driving force. Reptiles use it to raise their blood temperature and become active, birds shift their ground and, in concert with moisture, it ripens seeds and fruit and promotes vegetation growth which produces oxygen.
In early morning, I have found birds along the shady, south-facing shore of Baroon Dam to be relatively quiet; while the sunny shore opposite is alive with noise and movement. Welcome Swallows, Fairy Martins and White-breasted Woodswallows perch out in full sun.
The Woodswallows huddle together on branches (called ‘clumping’) and additionally benefit from the warmth of companions. All three species hawk for insects over the water, adding extra warm-up value through exercise.
Coral trees on this north-facing shore still have flowers – like bunches of small, scarlet bananas on their branch ends. In the bright sunshine they are visited (and squabbled over) by a procession of Honeyeaters – Blue-faced, Dusky, Lewins, Brown and New Holland. Without the sun, we would see no flowers and nectar-feeding birds would have to look for other food.
It is energising warmth that frees up wildlife to relax from essential food searches and attend to pairing and the future of their species. Birds court and a male will suspend self-preservation as he finds and offers food to his mate.
Scientists have discovered that, as the days grow longer, a small part of some birds’ brains begins to grow. It is the part that controls song. As daylight expands, so does the variety and richness of the birds’ singing.
But now we live in a world challenged by so many unremitting symptoms of climate change, with an emphasis on increasing temperatures; yet the science of its causes and effects are there for all to understand. There is ironic tragedy in this, because life always has, and always must, come from the sun.