Subject: Re: Bird Migrations; Two Breeding Seasons?
Date: Jan 26 08:43:30 1996
From: Eugene Hunn - hunn at u.washington.edu


If birds can raise two or three clutches in one place in a season why not
two in two places?

Gene Hunn.

On Thu, 25 Jan 1996, Stuart MacKay wrote:

> Alvaro Jaramillo wrote:
>
> > Dave DeSante also believes that coastal California American
> Robins> nest here early in the season then move up to the Sierras to
> breed> a second time, he has some banding info to support this, but
> not
> > enough to convince anyone yet.
>
> This is suspected for a few species in Europe as well.
>
> Early each June in Scotland there is a fresh arrival of male
> whitethroats (Sylvia communis) which take up territories and start
> singing. I suspect these are birds from further south which may have
> failed breeding and are trying their luck further north where the
> Spring is just getting going. Proving this however will take some
> doing as the numbers of whitethroats banded each year in the UK is
> almost vanishingly small.
>
> A similar situation exists with dotterel (Charadrius morinellus). A
> male was banded while sitting on a clutch of 4 eggs at Drumochter
> Pass, Scotland in late May. Six weeks later the bird was seen on the
> Hardangervidda in southern Norway with a brood of chicks.
> Presumably the bird failed in Scotland and moved further north to
> try again (it's a bit far to walk and the North Sea gets in the
> way). There are also a couple of records of (color-banded) female
> dotterel seen on Scottish mountains displaying then seen a few weeks
> later in southern Norway.
>
> Whether birds in the UK migrate between broods is open to question.
> I suspect not, given that the weather conditions are relatively
> benign, with no summer "drought" typically associated with large
> areas of the US.
>
> Still I think it's a matter of time before this "opportunistic
> migration" is demonstrated as a real breeding strategy. The only
> thing hampering its demonstration is a lack of banders ;-)
>
> See ya,
>
> Stuart
> ---
> Stuart MacKay
> 220-301 Calibre Chase Drive
> Raleigh, NC 27609
> ph:(919) 832 0353
> email: stuart at blarg.net
>