Longevity of Australian passerines

["Philip Veerman" <>]

That is a big call. Yes it could happen. As in I think Martin is suggesting selection for those individuals to live longer, driving evolution towards evolving greater longevity. Fine if that variability exists in a genetic form that can be passed down. However equally or more likely is that the variability does not exist, and if the pressure exists (and continues to a critical point) and there is not the ability to adapt quickly enough, far from promoting greater longevity, it simply leads to extinction.

 

As for other than the ‘stressful migration’ theory, the other speculation that Harvey mentions. I don't see any exclusion between these ideas. Surely it is reasonable that they and likely other factors apply jointly and to variable extents in different places or to different species.

 

Philip

 

-----Original Message-----From: martin butterfield [ Sent: Thursday, 24 January 2013 7:32 AM      To: Perkins, Harvey
Cc:       Subject: Re: [canberrabirds] Longevity of Australian passerines [SEC=UNOFFICIAL]

Harvey

Since, as I understand it, one of the impacts of climate change is that weather becomes more variable would this theory imply increased longevity for N hemisphere species?  I have no idea how that could be assessed in human timescales.

Martin

On 23 January 2013 15:12, Perkins, Harvey <> wrote:

And other than the ‘stressful migration’ theory, the other speculation that I’ve heard relates to the variable climatic conditions experienced by Australian birds.

 

I have no references, but it goes along the lines that climate is so erratic or unpredictable from year to year, e.g. droughts etc, that birds in Australia tend to have different breeding and life strategies than birds in the northern hemisphere with more predictable climatic conditions. Birds there have large clutches and timing of breeding tends to be very tightly tied to the season/time of year. In Australia birds tend to have smaller clutches and tend to be more opportunistic in when they breed. This is linked to a survival strategy where it is better for an individual bird to survive for many years and weather (sorry – bad pun) the bad conditions and live to breed again, rather than put all their effort into a few shorter but more prolific breeding efforts.

 

Something like that, anyway. I’m sure someone can come up with a better explanation and references.

 

Harvey