As Michael Lenz knows, I have made intermittent starts on a lengthy piece tentatively titled “Where do Dusky Woodswallows go in Winter?”. Below is an extract on the larger numbers observed locally. Incidentally, the conclusion is that they move, in flocks, to a broad crescent stretching from the SA/NSW border to New England, with the position of the crescent varying from year to year according to conditions, and with Canberra falling within the southern boundary in some years. The observations of Chris and Alex fit the pattern. The exit of DWSs from their southern haunts is more marked than the YFHEs, even if their through-movement here is less reported.
A site Barbara Allan has visited over more than 20 years takes in parts of the margins of Lake Ginninderra. At that site breeding numbers have fluctuated over the years. However, the phenomenon of flocking movers in April has been more evident there, with intervals between apparent departures and more flocks coming through, for example 70 at end-April 1990 and 60 mid-May 2005, suggesting waves of movers from further afield.
2005 was a year with high numbers in June/July appearing at various sites. (To obtain a more complete picture of observations, it is necessary to consult the COG chatline archive as well as the records database.) On 9 July Marnix Zwankhuizen reported about 50 birds from two separate locations in Gungahlin. In the paddock to the west of the Kellys Swamp car-park, more than 80 were recorded by Sue Lashko on 21 July. They were within a 2ha survey, on the ground, in shrubs and on power-lines.
2007 was another year with high numbers in June/July (16 reports). There were several records from the Jerrabomberra wetlands area. On 15 June Steve Holliday recorded 40 in trees lining Dairy Road, and on 21 July Michael Lenz found 60 flying between Kellys Swamp and the nearby sewage ponds.
With the influxes in 2005 and 2007, observers reported variable numbers on different days at the same site. No attempt has been made to find records of intervening days with no birds at those sites, but they may exist. The numbers and patterns of occurrence suggest transient feeding flocks not associated with local colonies.
‘Moving flock’ observations of a different kind were made by Jack Holland in June/July 2010 (Holland 2010). He reported quite large numbers (22 on 12 June, 17 on 4 July) that were difficult to detect because they were circling high overhead. The sudden appearance of those birds suggested they had arrived from beyond the local area.
The record of Michael Lenz of 200 birds on 2 September 2006 is exceptional. It appeared on the chatline in this form:
From 16.52h onwards Dusky Woodswallows were gliding in a SW direction, using the updraft along the Mt Majura/Mt Ainslie slope …. Main appearance of DW around sunset though, in total 200 birds:16 + 26 + 8 + 150. The latter flock appeared just after sunset and went down over the woodland and must have settled for the night on Mt Majura.
Given the date, the record is evidently of an aggregation returning southward. It is the largest aggregation recorded in the Canberra area.
By contrast with those high numbers in some winters, only a single DW was reported in Canberra in June/July 2012. That was in a ‘Winter Birds’ project conducted through the COG chatline in which more than 40 experienced observers reported appearances of nominated species.
From: Alex McLachlan
Sent: Tuesday, 22 April 2014 11:17 AM
To: Canberra Birds
Subject: Re: [canberrabirds] Dusky Woodswallow
Yeah I've still got 100s DWs @ a couple of diff roosts in the hills near yass river. Orioles gone. Strangely no migrating honeyeaters or silvereyes over Easter.
Around 100 Dusky Woodswallows coming in to roost in pine trees along Jerrabomberra Ave in Narrabundah this evening. It was quite a spectacle! Definitely the largest flock I've seen of this species.
I had several Dusky Woodswallows flying very high over my house on Wednesday and Thursday. I don't know how many. Most I could see at one time was 3 but mostly I could only hear them.
I also had an Olive-backed Oriole in my neighbour's jungle yard, feeding on figs, last week.
Wayne/Ann, of the summer migrants Duskies are among the last to leave, and along with the Olive-backed Oriole stay in reasonable numbers until about the first or second week of May, though some stay and overwinter – the numbers that stay varies with in 2013 very few duskies present during the winter period.
Sent: Saturday, April 19, 2014 5:06 PM
Subject: Re: [canberrabirds] Dusky Woodswallow
A couple at Narrabundah Hill yesterday!
this afternoon on Uriarra Rd near Huntly Station a single Dusky Woodswallow – a late departee?