Sunday, 15 March 2015

Bird-a -a- Day 2015 rolls on

So on Friday 13th March the year has got through 73 days and i have managed to add a new bird to my year list every day.    As before I am using 2 series to score each observation:

  • A code specified by the organisers of Bird-a-Day indicating how 'usual' the species is in the area seen at the time of year seen; and
  • An index based upon the relative number of reports to eBird of each species in NSW.

The first of this is a bit subjective, especially when in an area with which I am not familiar.  The second is objective, since it involves no assessment by me, but is biased towards (ie gives a higher score for) the birds in areas where most people report birding - ie Sydney!

Here is a graph of the average level of each series for 2015.
I deliberately started the year with a rarity, the Powerful Owl that resided in Turner ACT for about 4 months.
This is definitely a rarity so got a BaD score of 6.  From then on things descended somewhat in BaD terms with the average score hovering around 3.5.  The number of species x code value is shown below:

BaD code number of species
not  yet used  396
2 16
3 28
4 19
5 9
6 3

The Owl is quite unusual across NSW with an index value of  15.  The latter series climbed quickly to an average of about 60 and has continued to gradually increase since then.  The rate of increase has picked up slightly in the last couple of weeks as I have started having to use to of the birds more common in this area.

To compare 2015 with 2014 I have decided to use the Index values as they are more objective.
It would be stretching a point to say the series are identical, but I'd suggest the term "broadly similar" is OK!

Comparing the two series species by species I found that there were only 33 species common to both series.  Thus there are 40 species only found in one of the two.  Since we have been around home for most of the time in both years I found that very surprising.

I have peered at the lists of mis-matches and can't come up with any great insights that explain a great deal of the difference.  Many of the birds on both mismatch lists were seen around Carwoola and while I got some unusual birds here last year (eg Rufous Fantails, Red-capped Robin) this years collection includes the equally unusual Nankeen  Night-Heron, Satin Flycatcher and Varies Sitella.  We had a couple of short trips away last year (to Wagga Wagga - spelt out in full to give OS readers a chuckle - and Port Kembla) and have had two, slightly longer in aggregate, trips this year to Bermagui and Mallacoota.  However these only cover a small proportion of the days.

My basic, and pleasing, conclusions are that:
  • the difference is simply a matter of choice between the various species offered more or less randomly on a day; and 
  • there are still plenty of readily-findable birds to add in this year's project.
A non-easy to find bird is the Great Crested Grebe.  So I was astonished to spot one when looking down into the Queanbeyan Sewage Works.

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