Well of course that is a big question that
G.Crompton asked and there are House Sparrow populations around the world that
are in decline. Not that all are consistent. There are many ideas about and most
relate to opportunities for feeding and nest building. Generally if adjoining
agriculture declined and people were more tidy then sparrows declined. These can
clearly be very localised impacts. Having said that, findings of decline
are occurring in most studies.
I was sent an advance copy of the new 450 page book
Birds in European Cities Edited by John G.
Kelcey and Goetz Rheinwald 2005. This book is an impressive compilation from 23
expert local authors, on the avifaunal communities of 16 European cities, in 11
countries. I actually had a small role in editing or refereeing a
couple of chapters, a few years ago, when the book was in very early draft
stage. There is a lot of interest developing about status patterns of urban
birds. The issue of House Sparrow populations rates several mentions (along
with many other species of course). This book is a research and status book
also useful for travellers, not a picture book or field guide.
Few places have consistently collected surveys of
continuous long-term data on bird populations, that have been published
that can answer the question, but this is one. The information on the species
from my book: Veerman, P. A. 2003 & 2006,
Canberra Birds: A Report on the first 21 years of the Garden Bird Survey.
is as follows:
"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
decline in the House Sparrow is occurring around the world, well at least in
Europe, so Canberra is not an exception. I have had correspondence with various
others and seen publications attesting to that. eg work of another Garden Bird
Survey, done in Holland.
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."
Interestingly I have had the following e-mail
discussion (recently) with someone from the ZOOLOGICAL SOCIETY OF LONDON who wrote to
me this week about the GBS trends, in particular following up about the House
Sparrow and its avian predators around the world. Extracts follow:
That is superb - you've certainly whetted my appetite to see the book!
I've just emailed our librarian declaring it to be an essential addition to the
collection, so hopefully she'll be in touch. The EGI library is in Oxford - not
too far away. There's probably also a copy in the British Museum Library at
Tring, as they're supposed to have "everything" on birds.
The items from the entries below that stand out for me
[Collared Sparrowhawk] declined to a low in Year 11
(1991) and since then has had a dramatic increase. For the first 14 years [House Sparrow] was the second most
common species but it has since declined. Wherever I
look, there is an almost relentless inevitability about finding increases in the
local small Accipiter where House Sparrows decline, and conversely no change in
status of the Accipiter where they don't. Granted your Currawongs have also
increased, but I somehow can't see a generalized, opportunist predator as a more
likely culprit than a specialist like the Collared Sparrowhawk - esp. as you
tell us that it's probably the predator most at home in suburban
Zoological Society of London
London NW1 4RY
ZOOLOGICAL SOCIETY OF LONDON
to which I have responded:
"If there is a connection between small
Accipiter increase and House Sparrows
decline, then I can see causative only in that direction (i.e. House Sparrows
decline could hardly cause a small Accipiter increase). It is indeed an
interesting connection, it makes sense, and if it helps, you are welcome to
cite this study as a consistent result. I wouldn't claim it on the basis of
this study alone, but then I didn't know anyone had found such a
connection. I'm sure there are many other factors involved. The Collared
Sparrowhawk here takes a lot of Common Mynas and Common Starlings too.
There may be partitioning between the sexes as to who takes what, as the female
is much bigger than the male."