Survival, seasonal abundance, sex ratio and diet of Eastern Spinebills Acanthorhynchus tenuirostris in the Blue Mountains, New South Wales.

Over 13 years (1977-1989) a total of 679 Eastern Spinebills was banded in a eucalypt forest at Blue Gum Swamp Creek, Winmalee, New South Wales. Compared with another population of Eastern Spinebills in the New England National Park, the one at Blue Gum Swamp Creek appeared to have a higher proportion of sedentary birds, had a higher survival rate and the birds that arrived during the 'winter influx' were less regular in their return to the site. There was a skewing of the sex ratio in favour of males, which was instigated during the birds­ first year of life. The effect of fires in the surrounding area is examined in light of the yearly variations in capture rates. Major food sources during autumn, winter and spring, were determined from foraging observations and identification of pollen on the birds. The major food plants included Banksia oblongifolia, B. spinulosa, Lambertia formosa, Grevillea mucronulata, Callistemon citrinus, Correa sp., Styphelia sp., Woollsia pungens and Amyema sp. Capture rates showed a substantial rise during May, June and July. This influx is more likely a passage of birds through the site and not a response to the flowering of food plants at the site. Morphometrics for both males and females are also presented.

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