Probably more individuals of this species pass through the area on
post-breeding migration than the number of any other species we have residing in
the area. This is the most regular of our species in terms of its monthly
pattern. COG has a long history of monitoring this migration (e.g. Davey 1986,
Wilson 1997 and Taws 1999). The calculation of abundance value "A" relies on a
weekly component. As this species is only abundant in the area for about eight
weeks each year, its average ranking in that scale, through the whole year, is
generally in the range of the 10th most common species. The migration peak
occurs in April, extending slightly from March and into May. Through June, July
and August there are always some still around and in September and October,
there is a second small peak about one fifth the extent of the April peak. This
is as some of the birds that survived the migration period towards the coast and
northwards, return through the city towards the Brindabella range to breed. The
difference between the size of the population between these two periods is
interesting. Another possibility is that in the spring return period the birds
may take a different route.
Interpreting numbers is difficult, for this species more than most. During
migration these birds fly past in noisy flocks generally stopping to rest on
tall trees and as this is well known, many people specially look out for them.
Their average group size of 9.83 is the highest for any honeyeater, because they
are mostly recorded as flocks passing through. Even with problems of reliably
counting numbers of these birds, there are marked changes in the birds?
abundance over the years. Year 1 had very high numbers, the highest by far with
an April "A" value of 34.4, Year 2 (which rated high for many other migrants)
numbers were very low with an April "A" value of 7.5. Probably breeding was well
down that year. Years 3 to 7 were very similar, midway. Then there was a
dramatic drop in Year 8 and continuing steady decline through to Year 13. That
has been followed by a steady rise, to levels still below those of Years 2 to 7.
For such an abundant species that breeds in enormous numbers very close to
Canberra, the paucity of GBS breeding records is notable. There were breeding
records of activity at nest in mid October and mid January and dependent young
in November, January and late February. One record in Year 9 at Site 32 had nest
and dependent young.
Graphs on page: 98, Rank: 16, Breeding Rank: 51,
A = 2.65986, F = 87.34%, W = 50.9,
R = 27.052%, G = 9.83.