Whistler Reporting Rates

To: "Geoffrey Dabb" <>, <>
Subject: Whistler Reporting Rates
From: "Kevin and Gwenyth Bray" <>
Date: Thu, 26 Apr 2012 18:42:50 +1000
At risk of being (pretty rightly) accused of getting involved in something about which, in detail, I know very little (I'm a very amateur bird-watcher, though I do have qualifications in science and economics of some relevance to the question I'm asking!), I would be interested to know something about the statistical "reliability" of the data shown in the last few days on rufus and golden whistler population time series trends and population seasonalities.  My sense is that only if the data are statistically sound can reasonably reliable general conclusions be inferred from them.  (I'm not for one moment suggesting there is a "reliability problem" - it's just that I've not seen any comment on the question, either way).
I am wondering (a)  what sample sizes are these data based on - essentially how many actual bird sitings and how many "nil" sitings from how many observation sites/areas are represented by each data point on the graphs; and (b) what proportion of the "area/region of interest"  (eg, the ACT if it's trends in the ACT that are being reported)  - or perhaps more usefully what proportion of the species' typical habitat' in (say) the ACT, was included in the aggregate data?
I ask these questions, in part due to prior experience in ostensibly scientific data and analyses on Southern Bluefin Tuna (SBT) population, when I was involved as a policy adviser in trying to interpret the analyses from what had turned into a major dispute between Australian and Japanese fish population scientists over SBT populations and "responsible" fishing quotas. 
To simplify the detail of the analysis, the dispute turned on significant differences in the two countries' scientists' methodologies in estimating (and projecting) current and future SBT populations.  In part, an element in the different analyses and conclusions was the extent to which  population data from a set of "sample areas" which necessarily covered only a small proportion of the total range of SBT could, or could not, be regarded as "representative".
So, to put my questions that way, can you be confident that the whistler (both species) sample areas used in the data/analysis that have are now being presented and discussed are "representative" enough , and the number of sitings made (whether positive or not) large enough to enable reliable inferences to be drawn?
Thank you.
Kevin Bray

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