Parrot population data and a question for birding aus members

[Martin Butterfield <>]

Taking Sonja's point a step further, another possibility is that a lot of
birds die over Winter.

When I lived in the Eastern US someone authoritative expressed this in the
following terms (not rigorous but I think the concept works) :

   1. At the start of a breeding season there are x birds in the US.
   2. Each pair of them rears on average 2 young (which is another 'x').
   3. Thus at the end of Summer there are 2x birds.
   4. However by the start of the next breeding season there are only x
   birds again.
   5. Why isn't the US knee-deep in dead birds?

The answer offered to the final question is that a lot of them don't make
it across the Gulf of Mexico!   The timing of point 3 in Australia would be
April-May and the timing of point 4 is pretty much September-October.

Martin Butterfield
http://franmart.blogspot.com.au/

On 19 December 2017 at 15:15, Sonja Ross <> wrote:

> Hi Don,
>
> One reason in Victoria is that September and October tend to be our
> wettest months so birders may possibly spend less time out birding.   It
> could also be that if the birds are breeding in our spring, at least for
> part of the time, one of a pair could be sitting one eggs.
>
> Another could be that April is often Easter when people are often out
> camping and birding.  Successful breeding would also show up in increased
> numbers then before winter.
>
> Sonja
>
> On 19 December 2017 at 13:38, Donald G. Kimball <>
> wrote:
>
>> Sorry Martin but are you suggesting there should be more parrot sightings
>> in Sept/Oct?  I thought there were more records and birds present in
>> April/May.  Perhaps I need to scrutinize my findings more.  Thanks for
>> your
>> imput mate!
>>
>> Don
>>
>> On Mon, Dec 18, 2017 at 1:37 PM, Martin Butterfield <
>> >
>> wrote:
>>
>> > Donald
>> >
>> > Are you adjusting for the total number of checklists submitted?  If
>> there
>> > are more lists in Apr/May than Sep/Oct one would expect more records of
>> > parrots.
>> >
>> > Martin
>> >
>> > Martin Butterfield
>> > http://franmart.blogspot.com.au/
>> >
>> > On 19 December 2017 at 07:42, Donald G. Kimball <>
>> > wrote:
>> >
>> >> I use E-bird a good deal like many I suspect.  I have noticed a
>> pattern in
>> >> parrot data.  I looked at aproximately 30 species of parrots in NSW,
>> VIC,
>> >> NT and noticed that there are more recordings/sightings for most
>> species
>> >> in
>> >> April/May as opposed to Sept/Oct.
>> >>
>> >> I have my own ideas as to why this is so but would love some input from
>> >> local Aussies.
>> >>
>> >> Thanks very much!
>> >>
>> >> Don Kimball
>> >> <HR>
>> >> <BR> Birding-Aus mailing list
>> >> <BR> 
>> >> <BR> To change settings or unsubscribe visit:
>> >> <BR> http://birding-aus.org/mailman/listinfo/birding-aus_birding-
>> aus.org
>> >> </HR>
>> >>
>> >
>> >
>> <HR>
>> <BR> Birding-Aus mailing list
>> <BR> 
>> <BR> To change settings or unsubscribe visit:
>> <BR> http://birding-aus.org/mailman/listinfo/birding-aus_birding-aus.org
>> </HR>
>>
>
>
<HR>
<BR> Birding-Aus mailing list
<BR> 
<BR> To change settings or unsubscribe visit:
<BR> http://birding-aus.org/mailman/listinfo/birding-aus_birding-aus.org
</HR>