"Migrants": is this early?

To: "'Canberra Birds'" <>
Subject: "Migrants": is this early?
From: Terry Korodaj <>
Date: Wed, 03 Sep 2008 11:23:55 +1000
Hi John

Your observations do not appear to be isolated for bee-eaters in northern Australia. There is some speculation on exactly what happens but it seems that in overwintering migration (i.e., moving north) observers see the current migrants leaving and then subsequently observe the same species during the overwinter period. It is perhaps likely that overwintering birds (new arrivals) are in fact migrants from further south who take up similar habitat, or at least occur in the same general area to the breeding season birds. The gap in departure/arrival dates that you observe is interesting as it suggests that local birds may in fact not be resident. Are bee-eaters present in Katherine? All year?


John Cummings wrote:
I used to live in Gympie in QLD and each year around the beginning of
winter and spring the population of rainbow bee-eaters would disappear
for a couple of weeks and then reappear.  I often wondered if the summer
mob moved north for the winter and their spots were then taken by some
from further south.  The reverse then happened in spring.

If there are any answers to this I am very interested.


John Cummings
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-----Original Message-----
From: Terry Korodaj Sent: Wednesday, 3 September 2008 9:17 AM
Subject: Re: [canberrabirds] "Migrants": is this early?

I strongly agree that we know very little about movement in Australian landbirds and would like to add a few points to the discussion. I am currently studying partial migration in rainbow bee-eaters and I just can't help myself...

Without getting too hung-up on definitions it may help to clarify that 'partial migration' is not really a question about migration distance, per se. The term is generally applied to species in which one or some members of a population remain resident, while the remainder migrate, or

some sub-populations within the entire distribution of a species remain resident, while the remainder migrate. Interestingly, the latter appears

to apply to rainbow bee-eaters at least in northern Australia, yet they remain a 'true migrant' in the south. Geoffrey's point about observing 'migrants' or 'residents' at the edge of their distribution is valid and

may have helped to create confusion around whether an individual bird (or population) is in fact present all year round.

There are many interesting questions that the study of partial migration

in a particular species might pose:
- why migrate? why stay? why have two strategies?
- who came first - the migrant or the resident?
- what is the evolutionary direction - more migrants or more residents?
- how flexible is the adaptation to migrate or remain resident?
- will climate change produce more migrants or residents?
There are many more, however, check out Ken Chan's great work on Silvereyes which apparently switch from being migratory to taking up residency in successive years (partial migration) - now that is cool!

Incidentally bee-eater arrivals in the ACT (COG Atlas data) seemed fairly 'tight' (10 days either side of 5 October), yet there has been a drastic decline in arrival dates since 2000 with no records for many years (2000-2, 2004-6). This could be an artefact of data collection but

I am checking out this trend for NSW and Vic.


Geoffrey Dabb wrote:
Like Peter Ormay, I think Martin's work on this is interesting and valuable - including his note on 'tight-arrival' migrants in this months Gang-gang. However, I sometimes think it can be misleading to focus, like the figurative eagle-eyed contributor to The Times, on the

'first arrival' of migrants - in relation to so-called partial migrants. For one thing it diverts attention from the true migrants, whose movement variation might conceivably reflect climate shift and
just local food availability.

Clearly enough, the GBS records movement of birds through the suburbs.

Thus there is clearly a seasonal element to the /garden/ appearance of

Grey Fantails for example.  With such birds there is quite likely (a)
altitudinal element and/or (b) a vegetation element eg to/from
Taking 'Canberra' as including its woodlands, it seems to me that insufficient work has been done to be certain of the annual movement pattern of birds that are present in our area during Winter, although
much reduced numbers: eg Noisy Friarbird, Dusky Woodswallow, Olive-backed Oriole (remember Graeme Clifton's report in July). The second BA atlas, with the first COG atlas, is a start. Other movers that can be present in Winter in reasonable numbers include Welcome Swallow, Black-faced Cuckoo-shrike, Rufous Whistler, Yellow-faced and White-naped Honeyeaters and Fan-tailed Cuckoo. I have difficulty with

the idea that any of those birds have 'just arrived' when they are reported in Spring.

The term 'partial migrant' seems to me to be confusing shorthand. It might suggest that some members of a population migrate only a short distance, or that some members do not migrate at all. With regard to the species in question it may be that Canberra is properly regarded
at the fringe of the Winter range and a few members of more southerly populations range about our area.

To me the 'true migrants' among our land birds are those that are
from South-east Australia in Winter, eg Koel, Bee-eater, Dollarbird. Significantly, it is these that seem to have 'tight' arrival schedules

(which makes all the more interesting the 'early Koel' reports). I would also include the Painted Honeyeater, which you can set your calendar by at Cocoparra.
*From:* martin butterfield 
*Sent:* Monday, 1 September 2008 5:04 PM
*To:* COG-L
*Subject:* [canberrabirds] Dusky Woodswallows

This afternoon a flock of about 6 Dusky Woodswallows were hawking
Whiskers Creek Road (about 200m outside my GBS site).

In terms of GBS observations this coincides nicely with the expected upturn in number of observations. A graph is attached: note that this

shows the raw number of observations rather than the F% value, since
two lines are similar and this one is slightly simpler to plot.  I
also extended the graph to show that the observations (after the
'surge") are less consistent than was the case for the Noisy


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