Bautista, L.M., J.C. Alonso and J.A. Alonso. 1992. A 20 year study of wintering common crane
fluctuations using time series analysis. J. Wildl. Manage. 56: 563-572.
Abstract: The numbers of common cranes (Grus grus) staging and wintering at
Laguna de Gallocanta (Gallocanta), northeastern Spain, have increased
throughout the period 1970-90. Consequently, we modelled the use of this area
by cranes using Box-Jenkins Time Series Analysis to evaluate the influence of
local food availability, duck hunting, and habitat and food conditions at other
more traditional crane wintering areas in southwestern Spain on Gallocanta
crane numbers. Food availability was not correlated with crane numbers at
Gallocanta except during mid-winter. However, restrictions on duck hunting in
1973 and its total prohibition in 1981 correlated with increased crane numbers,
and probably provided the most immediate reason for this increase. Habitat and
food conditions at other wintering areas had no apparent influence upon crane
numbers at Gallocanta. Because annual productivity figures were not correlated
with the observed increase, we suggest that a northward shift in the wintering
range associated with food provided by agriculture, together with a possible
decline in mortality due to legal protection along the species' migratory
route, probably have been major long-term factors contributing to the increase
in cranes wintering at Gallocanta.
Study published in 1992 in the scientific Journal of Wildlife
Management (vol. 56, págs. 563-572), edited by The Wildlife Society . Reproduced
here after the authorization was granted by the editorial office.