Re: non seasonal mating in birds question (2)

[evelyn sobielski <koreke77@yahoo.de>]

> Since there are no real seasons in the tropics
> (except for 'wet' and 'dry'), 
> I *suspect* that seasonal breeding cycles are far
> more relaxed close to the 
> equator.

In some cases. Generally, bird reproduction is
terribly expensive by comparison... there are no real
r-strategists in birds, though there ist a notable
tendency to r-ish strategy towards the neornithean
base (K-strategism is almost nonexistent in
paleognaths and generally apomorphic in Galloanseres).
Interestingly, also in *some* Passeriformes it tends
strongly towards r.

Birds' reproductive cycles therefore tend to latch
strongly to seasons of plentyful resources, however
they are defined.

Pelagic seabirds I suspect are largely following
endogenous cycles. There is the famous case of the
Guadalupe _Oceanodroma_, the "white" albatrosses
(evolved twice aming these) etc.

I have field data of temperate-tropical habitat where
there are generally breeding seasons as pronounced as
in temperate regions. The difference is maybe a
tendency towards multiclutching (2 or seldom 3; I
think more does not occur on any substantial basis) in
temperate climate. In mildly seasonal subtropical
climate in the outer tropics (warm pampas, yungas,
humid Capensis, E African montane forest etc) there is
usually an equally restricted breeding season, but
with a wide unimodal spread.

Re-mating between clutches in multi-brooded birds is
known. Plenty of studies exist for Acrocephalidae,
where the trait is famously plastic.


Regards, 

Eike


      Lesen Sie Ihre E-Mails auf dem Handy.
www.yahoo.de/go