Hi All,
About Sparrows and Starling decline, yes it is true (or at least clearly was
true from 1981 to 2001) the following texts from the GBS report is of
relevance. As data exists and they are COG's data (although this is my
interpretation), we may as well use it. Also it is worth mentioning that the
House Sparrow is also in drastic decline in UK and Europe and this is being
reported on separately.
>From the text on page 7:
"Woodall (1995) provided results of the 1979-80 survey. He presented
information ranking the species, in a manner similar to the GBS components
of COG's ABR. He found that only one introduced species (House Sparrow) was
a dominant species (more than 5% of the bird population) as defined by
Huhtula & Jarvinen (1977). To test seasonality, the year was divided into
two halves, spring - summer and autumn - winter. On this basis there were
significantly higher numbers of individual birds in autumn - winter than
spring - summer but there were no significant differences in the mean number
of species. The Canberra GBS reached more specific results on seasonality.
Woodall (1996) used the results of the Queensland survey in an attempt to
explain the uneven distribution of House Sparrows in Brisbane in terms of
their association with other species. House Sparrows had negative
correlations with Noisy Miners and Grey Butcherbirds and positive
correlations with Silvereyes and a range of other small birds. Multivariate
cluster analysis showed that, on the basis of their common bird species,
Brisbane gardens could be divided into two distinct groups: those with Noisy
Miners (and other large species) and those without Noisy Miners, having a
range of small species. In Canberra the Noisy Miner and Grey Butcherbird
comprise a small component of the bird fauna."
>From the text on page 17:
"Year 1 of the GBS was not the start of bird populations in Canberra and
Year 21 was not the end. Many species show trends in abundance in Canberra
and the end point of these trends has not yet been reached. Of the species
increasing or decreasing, when will these trends even off? An obvious
question relates to the increase in the Common Myna population and decrease
in the Common Starling population. How long will that continue and will the
two species reach equilibrium?"
>From the text on page 47 (about introduced species):
"The only dominant species, more than 5% of the bird population (Huhtula &
Jarvinen 1977) in Canberra are the Common Starling, House Sparrow and
recently the Common Myna. Of the rest, two more are ranked within the top 32
most often recorded species (with the next one at 113). The 21 years results
show that the Common Starling and House Sparrow have been the two most
abundant species, though both are in decline. The Common Myna has shown a
dramatic increase in the same time. The increase in this species is of
concern because of its nest competition with other birds."
>From the text on page 49:
"It would be wrong to interpret too much cause and effect in these data,
though there are suggestions of linkages. Most obvious is that the increase
in the Common Myna matches a decline in the Common Starling. Both species
are likely to reach a steady state in the top ten common species (unless
some action is taken). Over that time, most of the larger parrots have
increased drastically, even though the Common Myna has been strongly
implicated as a nest competitor."
And from the species texts:
House Sparrow Passer domesticus
This is a species well known for their strong dependence on human habitation
(Summers-Smith 1963). This species is more common in the urban (town
centres, major shopping centres) than suburban environment. For the first 14
years it was the second most common species but it has since declined. The
monthly pattern is quite regular but of small amplitude. From a November
low, rises to the March peak. This is associated with breeding. Apparent
numbers decline as birds are nesting, due to birds being out of sight and
the fact that much nesting occurs around town centres and buildings away
from garden areas. The March peak represents the impact of flocks of newly
independent juveniles. Winter numbers are fairly uniform. The fact that July
abundance is higher than that of June (eleven months later), is most likely
due to the steady population decline of the species. The abundance has
declined smoothly and markedly, particularly from Years 6 to 21. This is
clearly a valid result as this is a widespread species. However, it could be
a long-term undulation as the population was increasing from Years 1 to 6.
Breeding records were highest in the mid 1980s and have declined since. Nest
building and other activities at nest commence in mid-September but most
breeding activity is from October to January. There is a large overlap with
many nest activities commencing late, these are rarely followed by
observations of dependent young. There are few dependent young after late
February.
Graphs on page: 104, Rank: 11, Breeding Rank: 9, Breeding graph on page:
107, A = 7.07589, F = 96.11%, W = 52.0, R = 73.676%, G = 9.60.
Common Starling Sturnus vulgaris
Overall our most common species on almost every year. It was the most common
species for the first 16 years, thereafter having declined to fifth by Year
21. In the late 1980s, concern about the status of the Common Starling was
sufficient for the ACT Government to engage COG in a survey of distribution
and movements of its post-breeding flocks. The report of this study by
Crawford (1990) lists locations of major feeding and roosting sites and
discusses problems of monitoring and controlling this species. It highlights
the population size at that time. It is clear that the Canberra population
of this species has declined significantly since then, as also shown by the
results of this study. Since then, although the species is still abundant,
the huge congregations formerly found are now mostly replaced by flocks of
less than 100 or even 50 birds. The monthly pattern is very regular with a
fairly even broad peak in numbers from January to May. Then a smooth but
dramatic drop to about half the numbers in October, followed by a rapid rise
to the January peak. Available GBS and other data imply a link between the
increase in the Common Myna population and the reduction in the Common
Starling population. These data were not available ten years ago and
Crawford (1990) did not mention them. Another likely cause for the decline
of this species is the reduction in the preferred feeding habitat of large
flocks of this species. The total area of grassland, such as sports and
school grounds, that were regularly irrigated, has declined in recent years
compared with the situation in the late 1970s and early 1980s. Also, numbers
were disproportionately highest in Year 1 due to a survey bias. Flocks of
over a thousand birds regularly roosted in a Pyracantha bush clump at Site
52. These trees were removed after that year and those big numbers did not
occur again. When the numbers were recalculated without this site, then the
A value was still highest that year but the reduction showed as smooth
rather than dramatic. Numbers have decreased over the first nine years from
A=25 to A=9.6, then showed a slight resurgence for the next four years. It
then showed a sharper decline from Years 13 to 21. In recent years there
appears to be a marked change in its distribution. It has declined more
dramatically on the northern side of the city than on the south, thereby
creating a marked difference that did not occur in early years. Breeding
activity occurs earlier than with the Common Myna. Nest building activities
commence in July, peak in September and are finished by January. Nests with
eggs or young commence in July, peak in October and are finished by January.
Dependent young commence in September, peak in November and December and are
finished by March. Duration of complete breeding event is about 14 to 17
weeks. There are often either second broods or more than one breeding event
included in one breeding record.
Graphs on page: 105, Rank: 9, Breeding Rank: 5, Breeding graph on page: 107,
A = 10.92630, F = 96.50%, W = 52.0, R = 71.241%, G = 15.34.
So, fortunately, a lot of this information is already out there.
Philip
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