More Satin Bower Birds in Higgins

["Philip Veerman" <>]

Martin is sort of giving another slant on 'logical' birds and I agree with Martin: "them's the rules". Martin wrote about and the possibility of two birds seen at widely different times I support his conclusion. In the situation of two birds seen at widely different times the number is most definitely ONE. Also for say a male for 3 days and then a female for the next four days, that is still one bird. As (without any further information) the area is only supporting one bird.

 

I was however referring to when you reach and obvious conclusion of clearly more than one bird simultaneously present in the area. This through repeated and frequent observations e.g. several times within one week or preferably several weeks, and when those times intergraded, when by some strange event you just happen not to have seen two birds at the same time in that week. 

 

I had Australian Ravens nesting in my big tree last year. Some days I did not see both simultaneously, mainly because I knew that the bird sitting on the nest was not visible until it arrived or left and I could not tell one from the other. If I was away for most of the week and the some day extended to a week, maybe (although I don't know if that ever happened) I did not see both at the same time for a week, even though over a period of months they were seen often and clearly both there throughout the time. This was a logical 2.

 

And I agree entirely with Martin's comment on 'estimation' and I hope we all understand it as such.

 

Philip

-----Original Message-----
From: martin butterfield [
Sent: Thursday, 20 October 2011 4:50 PM
To: COG List
Subject: Re: [canberrabirds] More Satin Bower Birds in Higgins

The actual words on the Chart are
reasonably clear: 
> "For each species observed (heard or seen) record the
>   maximum number of individuals occurring in the area at any one time during
>   that week.  When you do not know the actual number record your best
>   estimate do not leave the number blank."

I place great
weight on physical presence as covered by the words "seen or heard".  I do
not believe we should include 'logical' birds such as might arise from thinking
about the possibility of two birds seen at widely different times meaning they
were both there at once.  I interpret the reference to 'estimation' as
covering situations such as a rapidly moving flock hurtles through the site and
one can estimate there were about 10 rather than being certain
that there were not 9 or 11.

Martin

On Thu, Oct 20, 2011 at 3:05 PM, Philip Veerman <> wrote:

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