Don the C++ Guru ;-) sez:

> What do you know (in general) about using juv. vs. adult
> ratios during migration to estimate breeding success? For any
> species, I mean. Has anyone attempted to correlate such
> information for a given species with surveys of the breeding
> population?

I know it's been looked at in Europe for Dunlin and Brent Goose, especially
in the Wadden-Sea area and in South Africa for Little Stint, Curlew Sandpiper
and Knot by Les Underhill (University of Cape Town - I think) and Ron Summers
(Royal Society for the Protection of Birds, Highland Office).

Looking at the proportion of juvies first lead to the idea the the
proportions were varying in cycles, 3 years for some populations, 4, 5 and 6
for others. The connection, originally ridiculed (like most good science) was
Lemmings - lots Lemmings lots of birds and the converse - all Arctic Fox and
Jaeger food.

It's very hard to make any definite connections to populations unless
programs of large scale color-banding of arctic species takes place - a sort
of impossibility but a nice idea all the same.

In the UK work is being carried out on wintering geese and swans by the
Wildfowl and Wetlands Trust (Karl Mitchell, Chris Thomas). Whooper swans,
Barnacle Geese and Greenland White-fronted Geese are being monitored in winter
time as a follow up from summer expeditions to Iceland, Greenland and
Spitsbergen. The geese and swans ramain as families when they get to the UK so
the breeding success of pairs identified on the breeding grounds can be
followed.

Stuart MacKay