Field choice in spring and breeding performance of Greylag Geese Anser anser in southern Sweden.

Abstract

Selection and exploitation of feeding areas by pre-breeding and nonbreeding
Greylag Geese A nser anser, as we ll as by families, was studied
in a breeding area consisting of four lakes in Scania, southernmost
Sweden, in the years 1997-2000. Total production of young in each lake
as we ll as the breeding performance of neck collared individuals was
established annually, 1985-2000. This breeding population increased on
average 15.3% p e ra n n um, from 93 pairs in 1985 to 910 pairs in 2001. The
two main field types used by pre-breeding pairs, males of incubating
females and non-breeders in flocks were win te r wheat and grassland,
often switching from the former to the latter in mid-season. Almost all
feeding during brood- rearing took place on pastures grazed by livestock
or on a golf-course. Generally in spring, the rates of exploitation were
below 300-400 goose days ha"1, but rates of >1,000 goose days ha' 1 were
noted for one cereal field and two grassland areas. The rates of exploitation
by families varied markedly among brood-rearing areas as we ll as
years, being highest all through the study period on a grazed pasture,
where it ranged 800-1,350 goose days ha'1. Including the utilisation by
non-breeders, the annual exploitation of this pasture ranged from 1,400
to 2,500 goose days h a 1. At the only lake without grazing by livestock
(since the mid-1990s), significantly fewer goslings survived to fledging
than at the other lakes (45% vs 70%). Indications of density-dependent
effects on the productivity of small young were noted at one of the lakes
(Klosterviken) but not at another (Yddingen). Most likely, the lack of any
density dependent effect, in spite of the very marked increase in the
breeding population during the study period at Yddingen, is the result of
access to highly fertilized grass on a golf course.