Paucity of Common Blackbirds

[Con Boekel <>]

Some interesting observations thus far on the Common Blackbird in the ACT.

Some personal musings on factors possibly to be added to be added to the drought meme:

The Song Thrush, a close relative has been extirpated from the ACT.

The Common Blackbird and Bassian Thrush co-exist in the ANBG.

In general the habitat of the Bassian Thrush appears to be more moist than that of the Common Blackbird.

Rapid increases in domestic water prices appears to be highly associated with the demise of watering of nature strips and domestic gardens and hence, presumably, of worm production.

There is a pattern of increasing proportion of hard surfaces in the newer suburbs and in gentrifying older suburbs.

Speculative: patterns of urban park management increasingly involves the removal of lower branches and associated rough vegetation.

Speculative: there is a long term trend in reduction in backyard space dedicated to vegetable growing and the associated rich worm production.

Urban upgrade/urban amenity projects, such as that abutting the northern end Commonwealth Bridge, destroy patches of rough/ground level vegetation which formerly provided protection for small birds.

Speculative: new domestic garden design appear to be less amenable to worm production.

regards

Con

On 10/6/2019 9:11 AM, Graham Gall wrote:

I agree that they are very scarce. I do a lot of birding and have only seen one in recent months in the Mt Annan Botanic Gardens- see pic here 
https://www.instagram.com/p/B2KbeL_h9xg/?igshid=i4qhutym3m0y

Cheers

Graham

Sent from my iPhone

On 6 Oct 2019, at 8:58 am, Geoffrey Dabb <> wrote:

Another factor is blackberries.  They are often found where there are extensive blackberry tangles. I was going to look for a correlation with R-b Finch, but COG website is down. JWNR and Molonglo margins probably have their full Blackbird quota from a territorial viewpoint.

 

From: Michael Lenz <>
Sent: Saturday, 5 October 2019 7:42 PM
To: Terry Munro <>
Cc: Philip Veerman <>; Canberra birds <m("canberrabirds.org.au","canberrabirds");" moz-do-not-send="true">>; John Layton <>
Subject: Re: [canberrabirds] Paucity of Common Blackbirds

 

 Common Blackbird numbers would would certainly be affected by two years of very dry conditions.

 

Michael Lenz

 

On Sat, 5 Oct 2019 at 19:16, Terry Munro <> wrote:

I've always thought that Currawongs keep the numbers of Blackbirds down with their predation of nests

Terry Munro

 

On Sat, 5 Oct 2019 at 7:05 PM, Philip Veerman <> wrote:

An interesting observation from John. I have been thinking the same too. Certainly is well down in numbers around my place. Only occasionally seen recently, rather than the usual daily of years ago. The GBS Data is not so easy to track from the ABR but it certainly suggests a decrease. Last year’s Abundance: “down 54% on the 30 year average.” From the last ABR the species was ranked 31 on abundance. From The GBS Report it was ranked 15, although that is ranking on number of records. Quite likely dry soil conditions are the main cause of their decline. Harder to find worms and other invertebrates in the soil layer.

 

The info from The GBS Report is inserted here. The annual pattern as shown on the monthly abundance graph is quite smooth and variations through the year are so small that there is no suggestion from that, of altitudinal migration.

 

Common Blackbird Turdus merula

This is a species that is common and conspicuous. Males sing during the early mornings of spring time. At

any time the species’ clanking flight and alarm calls are easily detectable. This bird is at home in gardens,

either open lawn or amongst messy leaf litter, feeding on soil invertebrates and soft fruit. It has a very regular

monthly pattern, though with a minimal amplitude. There is a low in February then increases to a December

peak then decreases down to the February level. It is quite common to find dead adult males during the

midsummer heat, though that seems unlikely to have such a dramatic impact on the total numbers.

Abundance increased smoothly from Years 1 to 10 and then has only marginally declined over the last six

years, though the range has been small. As the species is widespread, this is clearly a true result.

This species is unusual in that the number of observations at the nest far exceed the number of observations

of dependent young. This is probably because it commonly breeds in well hidden nests in vegetation very

close to houses and dependent young are not especially conspicuous for long. Breeding records consist of

activities at nest over a broad period from mid August to late January and dependent young from mid

September peaking in December to late February.

Graphs on page: 105, Rank: 15, Breeding Rank: 6, Breeding graph on page: 107, A = 1.73186, F = 91.96%,

W = 52.0, R = 72.172%, G = 2.40.

 

From: John Layton [
Sent: Saturday, 5 October, 2019 5:58 PM
To: Canberra birds
Subject: [canberrabirds] Paucity of Common Blackbirds

 

Yesterday afternoon I saw a male Common Blackbird perched quietly on an electrical cable. This is the first blackbird I’ve noticed in our garden since early last winter.

 

Five weeks into spring, I would expect to see two, sometimes three males, pursuing each other helter-skelter through the garden almost every day and, on calm spring evenings, an hour or so before and beyond dusk, a dominant blackbird would occupy a prominent perch and regale the neighbourhood with a cascade of melodic notes. But not this spring. So where have they gone? Perhaps it’s too obvious to suggest they’ve moved to littoral areas where worms may be closer to the soil surface.

 

Incidentally, does anyone know if there’s published work on the movements of Common Blackbirds in s. e. Australia? I somehow suspect altitudinal movements in addition to drought related shifts. Other than HANZAB I’ve not found anything.

 

John Layton

Holt.