A Bird in the Bush: The Blue Mountains

Sunday, April 22, 2012

The Blue Mountains

I have done a number of day trips with Follow That Bird which I have always thoroughly enjoyed. Well organised, the trips take in the best spots for the time of year, and with knowledgeable guides and an interesting bunch of people a great day’s birding is guaranteed. We were picked up by the bus at Killara after a foggy drive for me down the F3. But as we waited the fog started to lift. I was a little chastened to realise that we all immediately recognised each other as birders: a certain age, wearing muted colours, sensible shoes and a shady hat – even with the bins slung around necks or suspended from high tech harnesses.

Yesterday our destination was the Blue Mountains to observe the autumn honeyeater migration.

On the way out of town we saw the usual urban birds:

Common Myna
White Ibis
Magpie Lark
Welcome Swallow
Australian Magpie
Feral Pigeon
Little Corella
Laughing Kookaburra
Noisy Miner
Rainbow Lorikeet

First stop was Wilson Park in Wentworth Falls, the trailhead for the Charles Darwin Walk. Here we picked up our guide Carol Probets, an acknowledged expert in the birds of the region. From the park we also had good views of the migrating birds heading up the valley and pausing to rest on the dead trees. The fact that the birds migrate during the day and at tree-top level make them a relatively easy spectacle to observe.

The majority of the birds are Yellow-faced Honeyeaters. As I wrote in the Wikipedia article on the species, while there are resident populations of the Yellow-faced Honeyeater throughout its range, it is for the most part a seasonal, latitudinal, daytime migrant. During the autumn (March to May) it migrates north along the highlands and coastal fringe of eastern Australia to southern Queensland, to return in the spring (August to October) of the same year. The birds commonly move in flocks of 10 to 100 birds, but occasionally in larger groups of up to 1,000 or more birds. They move in successive flocks at a rate of up to several thousand birds an hour. Near Hastings Point in New South Wales over 100,000 passed through in a single day.

The species is able to detect geomagnetic fields and uses them to navigate while migrating. Experiments where the vertical component of the magnetic field was reversed indicate that the magnetic compass of the Yellow-faced Honeyeater is based on the inclination of the field lines and not on polarity, distinguishing between the direction of the equator and the poles, rather than north and south. While their flight is in one general direction, it is not in a straight line as the flocks stay in vegetated areas, negotiate gaps in the mountain ranges and detour around cities.

The migration of many birds in Australia, including honeyeaters, has generally been described as occurring mainly in response to external environmental stimuli, such as food availability or an influx of water. However, the Yellow-faced Honeyeater has been found to have a broad range of characteristics which are consistent with the adaptations of Northern Hemisphere migrants to their mobile lifestyle: an annual cycle of migratory restlessness; seasonally appropriate orientation based on magnetic, solar and polarised light cues; and a migration program based on the magnetic inclination compass.

We stopped for morning tea at Katoomba Falls Reserve. While the contact call of the Yellow-faced Honeyeater was with us almost continuously, also flying overhead were:

White-naped Honeyeater,
Noisy Friarbird
Silvereye
Striated Pardalote
Spotted Pardalote

Young Red Wattlebirds fended for themselves in the trees around our picnic spot.

Other birds we observed over our tea cups were:

Pied Currawong
Galah
Crimson Rosella
Sulphur-crested Cockatoo

The honeyeaters are channelled into narrow flyways by the peaks and valleys of the Blue Mountains – one of the narrowest of which is at Narrowneck. The bus parked before the Golden Stairs and we walked along the track towards the locked gate at the top of the rise. Highlights here were: