Christmas Bells

Christmas Bells
Christmas Bells - Blandfordia nobilis

Monday, March 27, 2006

Autumn evenings, and migratory Honeyeaters.

The wonderful cool freshness of Robertson evenings is seldom as comforting as in early Autumn.

Another comfort is Anni's blog, where she continues to intrigue us with the breadth of her imagination, and occasional clever photographs, such as today's self-portrait in a teaspoon (the photo is relevant to her story)

We have had a string of balmy days, with clear air, and temperatures in the high 20s, but dropping to the low teens, over night. Weather watchers could do worse than visit the "Mittagong Weather and Weather Cam" website. It is a weather statisticians dream.

My personal gauge of the changing of the seasons is the first sign of migratory Honeyeaters passing through. Yesterday I saw my first migrating Yellow-faced Honeyeaters (Lichenostomus chrysops) for the season. Today I saw a few more. There is no spectacular wave of migration with these birds, unlike images from Europe and North America of migrating Geese and other wildfowl.

These little birds drift to warmer climates, and to coastal feeding grounds, from their summer nesting grounds in the high country in southern NSW and Victoria. But they form small flocks, currently a mere handful of birds. They fly in small groups from one tall tree to another, in short distances of perhaps 200 metres at a time, then rest for a few minutes, then fly on. In a few weeks time, the numbers of birds in these groups will swell to 50 or maybe 100, and the frequency of the passage of these groups will also increase. Just because it is not a spectacular flight of passing birds, does not mean it is not a real migration.

I can tell these birds are migrating, quite simply, because they do not reside in the Yarrawa Brush over the summer. These Honeyeaters are birds of the tall Eucalypt forest, primarily. But they migrate to coastal heathlands, to arrive when the nectar-rich Banksias are coming into flower. So, over the summer I see none of these birds here in Robertson. But they pass through in autumn, and again pass through on their way back, in spring.

Incidentally, these birds do reside a mere 5 Kms away, on the sandstone based forests, down along the Belmore Falls Road. I am not saying that these migrating birds come from there, simply, just pointing out how specific their choice of habitat is. Belmore Falls, has sandstone-based scrubland and Eucalypt forests, with many proteaceous shrubs in the understory. That environment suits them as a breeding ground. The Yarrawa Brush, cool temperate rainforest country does not. The difference is primarily that our trees do not produce the kind of nectar supplies that these birds need. So they do not breed here. They fly through to get to other environments which suit them, for the autumn and winter seasons. Typically, that is the coastal heathlands of the NSW coast where many Banksias flower at the suitable time for them - autumn and winter. (Photo above is courtesy of the Macleay Valley Coast birdlist, on their Tourism website.)

Food sources is the limiting factor in this migration, by the way, not temperature. This is demonstrated by the fact that every year a small number of these Honeyeaters overwinter in the Australian National Botanic Gardens, in Canberra. Canberra has far colder winters than the Southern Highlands. But the Botanic Gardens has a cultivated collection of suitable food plants for these birds, with thousands of Grevilleas and Banksias, which flower over the autumn and winter seasons. So, a number of birds stay there, instead of migrating through to the coastal heathlands.

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