Subject: Re: Bird Migrations; Two Breeding Seasons?
Date: Jan 27 12:36:46 1996
From: Stuart MacKay - stuart at animal.blarg.net


Dennis Paulson wrote:

> For a rather different scenario, there is speculation that
> female Ruffs might mate with displaying males in the lowlands
> of western Europe in spring, then fly on to Siberia to lay
> their clutch, entirely unencumbered by those pesky males (who
> play no part in parental care but display to any female they
> encounter). No really good evidence, but a strong indication
> that many more females are inseminated at Dutch leks than
> breed in the area. A female nested in Alaska once, although
> the eggs were infertile.
>
> For this and much more about this fascinating bird, read The
> Ruff, by Johan G. Van Rhijn, T. & A. D. Poyser, London, 1991.

A hypothesis put forward by Van Rhijn associated with this, is that
satellite males - typically those with light coloured or
unpatterned ruffs would migrate further north in order to mate with
females closer to or on the breeding grounds where there would be
less competition from lekking males (satellite males do not lek).
The theory being that migrating incurrs a cost so males would mate
with females on southerly lekking sites in preference to flying
north to the breeding grounds.

Theunis Piersma tested this hypothesis by looking at the numbers of
satellite and lekking males at five research stations on the
Russian tundra. The result being that the numbers of satellite to
lekking males was not significantly different, hence Van Rhijn's
hypothesis has to a certain expent been disproved.

So the "mating in the south, laying in the north" theory may not
hold - more likely it's a good deal more complicated than that.

For more information the reference is:

Peirsma, T. 1995. Morph and sex composition of Ruffs on Russian
tundra in June 1994: are satellite males more prone to migrate
northwards than resident males ? Wader Study Group Bull: 31-32.

Stuart
---
Stuart MacKay
220-301 Calibre Chase Drive
Raleigh, NC 27609
ph:(919) 832 0353
email: stuart at blarg.net