Thursday, January 4, 2018

Annual Report 2017: 2017 compared with 10 previous years

A starting point is the number of species reported in each month.

In the table-image above (which becomes much more legible if you click it) the year in which the highest number of species was observed for each month is highlighted in green.  Most of these months occur between September 2011 and May 2013 when observer activity was at peak levels and abundant rain fell, leading to an explosion of water birds on the Hoskinstown Plain. However we did establish new high marks in November 2015 and April and June 2016.

While we usually short of observers (including this author) in the July, the row showing 2017 as a % of the average for the period since 2010 shows that we are still holding up.  Thank you to all observers who have contributed observations.

As reported in the overview we added 1 species to the list in 2017.  

18 species have been recorded in every month throughout the 9 years (obviously including every month of 2017) These are:

  • Australian Wood Duck; Galah; Sulphur-crested cockatoo; Crimson Rosella; Eastern Rosella; Laughing Kookaburra; White-eared Honeyeater; Noisy Miner; Magpie-lark; Welcome swallow; Yellow-rumped thornbill; White-throated treecreeper; Common starling; Grey butcherbird; Australian Magpie; Pied Currawong; Australian Raven; Little Raven.
A simple way of summarising the difference in reporting rate between 2015 and earlier years is by a tree diagram.

The number shown as 'same' is those where the % of available months (106 in total for earlier years, 2 months are missing) is within +/- 5%.   This allows for differential observer effort affecting the result by a small amount.
The pattern shown in that tree is somewhat different to that from 2015.  This "comparison of comparisons" is summarised in the following table.

Comparison with previous years
  less same more
2015    16  58  77
2016    27  64  60
2017    22  75   58
My conclusion is that the team of observers have got to a point where we know what birds are around and where to find them so the species with the same reporting rate are increasing while those getting reported more frequently are decreasing.

The next table shows the number of increasers and decreasers by category of bird.  (I should point out that these categories are rather arbitrary, but just provide a few groupings that cover birds of broadly similar behaviours and/or habitats.)

1  Waterbirds11520
2 Birds of Prey266
3 Parrots and Relatives054
4 Kingfishers and other non-songbirds499
5 Honeyeaters1102
6 Flycatchers and similar species474
7 Thornbills, Finches and similar species892
8 Other, smaller birds289
9 Other, larger birds071
Total 227657

Many of the changes have been hinted at in earlier sections. 

The high number of 'increasers' in waterbirds was somewhat of a surprise in view of the exodus of such birds referred to in several parts if this Report.   

In some cases - not only waterbirds - a rating of increaser may be an artefact of arithmetic, because 
  • a sighting a species in 1 month of 2017 (which infers the bird is unusual) is equivalent to 8.3% 
  • if it was only reported in 3 or less months of the preceding 10 years (quite likely for an unusual bird) it would still meet the "rule" for increase whereas in fact it was simply an unusual bird of about the same reporting rate.  4 Waterbirds and 2 others meet this situation. .
Also I, at least, have been more aware in recent years which water features were likely to be productive.  For example Musk Duck and (particularly) Black Swan are nearly always observable when looking down on Foxlow Lagoon (but nowhere else).

Flycatchers etc and Thornbills etc may be a cause for concern as they have several decreasers and few increasers.  Of course a single years observations are insufficient to prove this: I shall investigate further when I work out exactly how to do that.

The results for Parrots, Honeyeaters and Other larger birds all indicate a stable situation.

No group showed a noticeable drop.

Links to other sections of this report

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