Re occurrence pattern of White-throated Needletails.
As most of you would know from my writings on this line, I have 17 years
continuous data from Garden Bird Survey in Canberra. This comprises 1101
observer years of data. (No, White-throated Needletails are not garden birds
here, they are common over this area from January and peak in numbers in
March with very few by April). I had thought of doing a simple four way
statistical test comparing weeks over the 17 years using data presumably
available from the meteorology bureau. Weeks with rain / not with rain and
Weeks with swifts / not with swifts. Obviously the scale is rather broad,
though it may work. Summer rain in Canberra is usually storm associated and
generally discrete, by that I mean, we have long periods that are dry and
hot and short discrete periods of wet weather in summer. This would involve
a fair bit of effort but isn't difficult. All the data is computerised.
Would anyone be interested in this line? Does anyone in Canberra wish to
volunteer to do it?
Of course there are biases, I for one, normally go out at least once an hour
when I am home, to scan the sky for 20 seconds, when the weather looks
appropriate (find good raptors that way too).
PV.
-----Original Message-----
From: Merrilyn Serong <>
To: birding-aus <>; Mike Tarburton
<>
Date: Tuesday, 7 March 2000 23:17
Subject: White-throated Needletails
>Hi all.
>Carol Probets' suggestion that an association between White-throated
>Needletails and weather applies only to large or widespread flocks
>agrees with my observation of approximately 60 WTNs under mammatus
>clouds, which are associated with air turbulence, at around 8.30 am on
>29 Feb over Black Range State Forest in the Victorian Central Highlands
>(37 26 19; 145 37 46). Later that day, from 11.30 am there were 5 WTNs
>under a blue sky a couple of km to the south west (37 27 40; 145 36
>54). Another fine weather observation, not yet reported, was a single
>WTN at Toolangi State Forest, also Vic Central Highlands, at 10 am on 9
>Feb, on a fine warm day with no cloud.
>When I saw the 60 WTNs there were also several Tree Martins flying below
>them and about 12 Dusky Woodswallows lower still. Quite spectacular.
>Cheers,
>Merrilyn
>
>
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