More Satin Bower Birds in Higgins

["Philip Veerman" <>]

In the absence of any further information, the answer to the conundrum is definitely one. That has always been the case since the GBS started and is quite clear on each version of the GBS Chart instructions. The reason being: if it is the situation that your area can (or does) only support one bird of that species at one time, and thus there is a reason why you only see one at a time, then it would be wrong to report two. The situation Anthony described for the Satin Bowerbirds at his place at this point in time is probably such a case. Another reason is that we would end up with higher average numbers of sexually / age etc dimorphic species than those in which it is harder to distinguish individuals. The two groups of species would be counted differently. The first group would get more twos and the second group more ones. In some species we would add the number present at two times and other species we would not, simply because the observer would not know it is another individual. That would create a big and ridiculous bias in the GBS results. Also adding numbers present at one time to numbers present at another time (regardless of that we know they are different birds) can lead to absurd results, entirely biased by the number of times a person goes counting, such as shown in some of the Yellow-faced Honeyeater counts.

 

However that is just based on one observation. When considering other birds, especially very social species such as (sexually dimorphic and easy to know they are different birds) like Magpie-larks and King Parrots, if you look for a few more minutes or on another day, or listen to them calling to each other even if you only see one, then you probably will find that at some other time within the same week you will have both or more present simultaneously. Then the answer to the question is look again and then the answer will likely be two or whatever. In many observations that will be the real situation. If that doesn't change things, then the answer is still one.

 

If you regularly see a male and a female many times in the one week, especially on overlapping times but not at the same time, then you should think what are the chances that they are not both simultaneously present within that 3 + hectare area at any time during the week. Pretty small. Indeed it may indicate that they are nesting and one or other is hidden on a nest somewhere. (That does not apply to Satin Bowerbirds). Common sense would indicate that the answer then would be 2.

 

In terms of contributing to the GBS, the biggest wrong answer to the question is "I don't know how many there are so I won't enter any number". That is the same as an entry of zero.

 

Philip

 

-----Original Message-----
From: Anthony Overs [
Sent: Thursday, 20 October 2011 12:07 PM
To: Paul T.
Cc:
Subject: Re: [canberrabirds] More Satin Bower Birds in Higgins

Hi Paul and others

Since
moving to Mataranka St in Hawker in January I've seen a green Satin Bowerbird
once every couple of weeks or so, sometimes every week for a month (trying to
remember what's on my GBS chart...). In the past few weeks I've had a blue/black
bird visit on several occasions. He has also been seen by friends further down
the street. Haven't seen him for a week or so. He could be at your
place!

It has raised a GBS conundrum again. The maximum number of Satin
Bowerbirds I've seen in any one week at any one time is one, despite the fact
that I saw a green bird and a blue bird in the same week (at different times).
What is the total number I put on the chart?

Cheers
Anthony

On 20 October 2011 11:56, Paul T. <> wrote:

Howdy All,

Further to my email of yesterday detailing a first sighting of bower birds for me here in Higgins....... I was just down the street checking whether the bird I saw in evidence yesterday was there (I heard it in a large conifer two houses down from my place this morning when I was hanging out the washing) but I didn't see the black male bird of yesterday.  I did however see 2 green birds, but not close enough to tell you beak colour or anything like that for attempting to do any sex or age identification, even if I knew how.  One of these was calling in the usual distinct call of the species, but nowhere near as strongly or intricately as the black male I saw yesterday.

So... we have not just one but at least 3 bower birds apparently in residence in my street here.  Cool!!  Hopefully they might visit my garden for water at times.  Interestingly, I cannot see any evidence of a bower constructed as yet, but there are definitely blue items lying about in a cleared area, so perhaps the bower will be a future display addition. <grin>

Has anyone else heard of bower birds this far west in Belconnen?  Or have I missed other reports?

Thanks.

Cheers.

Paul T.
Higgins, ACT