Oh and one other thing, is that simply adding the totals of a species counted in the GBS by week, does not take into account the wide variation in the number
of observer weeks by week. So giving varying sample sizes of the counts. These data are shown in Figure 5 “observer weeks by month” and Figure 6 “observer weeks by week” of The GBS Report (page 26). Yes the differences for a small number of weeks over such
a long period is tolerably small, given so many other awkward features. It may not even show well in a graph of that scale. Of course the difference is greatest during December and such a graph would be inappropriate then but it also is a small issue at the
variable set of weeks that include Easter.
Philip
From: Philip Veerman [
Sent: Saturday, 23 March, 2019 10:07 AM
To: 'COG List'
Subject: RE: [canberrabirds] Honeyeater migration A "me too" moment - more Yellow-faced Honeyeaters- ? cold cooma weather
Yes a good graph but not notably unexpected. I also suggest that it is entirely consistent with what is showing this year. Historically, beginning the progress
towards the peak is occurs this week. That is what is happening now. A few mentions of relatively small flocks on an email chat line does not constitute high levels so far. There has been little if anything more than the usual start to this process so far
this year.
Also be aware that in the early years there was some clearly wonky counts of migrating YfH in the GBS. At that time, processes were not so well explained as
in later versions of the chart or as I started doing the “Annual GBS promotional spectacular”. These were obtained as people clearly tallied counts over a period,
rather than simultaneous. I recall one individual count of 10060. This is clearly not right. As I went through the process of compiling all
those years of GBS results, as I recall I substituted that 10060 for 500. That is one I still remember now. Of course that was not right either but at least it is close to credible for an exceptionally large set of flocks that could have been in the area at
one time. No way to know how many similar errors were made of this often hard to count phenomenon. I did not tell that story in The GBS Report but there is a strong hint of the problem of counting them.
I can’t guess what has happened since then (2002).
The relevant extract is this:
Yellow-faced Honeyeater
Lichenostomus chrysops
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.
Philip
From: Martin Butterfield [
Sent: Saturday, 23 March, 2019 9:22 AM
To: Nicki Taws
Cc: Jack & Andrea Holland; Jean Casburn; COG List
Subject: Re: [canberrabirds] Honeyeater migration A "me too" moment - more Yellow-faced Honeyeaters- ? cold cooma weather
I have added up the number of Yellow-faced Honeyeaters reported in each week of the GBS since its inception and obtained this graph.
The star marks this week. I would go with Jack that the flow is starting a week earlier than "usual". A possibility is that reporting the migration seen at Gigerline has catalysed observations
at other sites.
On Sat, 23 Mar 2019 at 07:32, Nicki Taws <> wrote:
The migration of Yellow-faced Honeyeaters typically starts in the last week of March, so these birds
aren’t too early. Given that we know the birds come from further afield than just the ACT mountains (CBN 29(1), 1-8) their movement could well be triggered by events that we are unaware of (such as the hailstorm). However I suspect that daylength would also
have something to do with it.
Cheers
Nicki Taws
0408 210736
From: Jack
& Andrea Holland [
Sent: Friday, 22 March, 2019 6:01 PM
To: Jean Casburn
Cc:
Subject: Re: [canberrabirds] A "me too" moment - more Yellow-faced Honeyeaters- ? cold cooma weather
Thanks Jean, very interesting. I’m not sure how widespread this was but it could be the reason we’re seeing some now.
I recall the forecast is for a warm dry autumn, so it will be interesting to see if there’s a gap once these come through, my understanding is that there is potentially a very wide catchment for the HEs that come through, including well into Victoria.
I’ve now checked my Gang-gang column for the past 3 years and around at the time of writing the April one (about 25
March 2016, 27 March 2017 and 28 March 2018) there had been few if any migrating flocks reported, so they’re definitely at least a week early this year, perhaps caused by your event (Page has now been added to the list of suburbs).
Sent: Friday, March 22, 2019 3:48 PM
To: 'Martin Butterfield' ; 'Jack & Andrea Holland'
Cc: 'COG List' ; 'Mark Clayton'
Subject: RE: [canberrabirds] A "me too" moment - more Yellow-faced Honeyeaters- ? cold
cooma weather
Last weekend Cooma had a severe hailstorm which was similar to a snowstorm on the ground. Perhaps
the cold temperatures have given the honeyeaters a false start – or the winter will be earlier than usual?
Jean
