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Wildl. Biol. Pract., December 2006 2(2): 72-78
MONITORING GREY PARTRIDGE (PERDIX PERDIX) POPULATIONS IN POLAND: METHODS
Polish Hunting Association, Game Research Station, Sokolnicza 12, 64-020 Czempiń, Poland
The grey partridge (Perdix perdix) population in Poland is monitored by
the Polish Hunting Association. Apart from information on hunting bag in
the whole country (1981-2002), also demographic data are collected every
year in selected areas (50-150 km2) located in various regions of Poland
(three such areas in 1987-1990, 12 in 1991-1997, and 19-41 in 1998-2003).
In the monitoring areas, spring partridge density (call counts in March/
April), reproductive success (counts of adult and young birds in August)
and annual survival rate of adult birds were estimated. The annual partridge
hunting bag in Poland varied from 24,000 to 293,000 individuals between
1981 and 1992, and decreased to 20,000 - 22,000 birds in the years 2000-
2002. In the 1990s, the average spring density of grey partridge in Poland
showed a 3-fold decrease. In the early 2000s, 0.5 to 10.5 pairs per km2 were
recorded in individual areas. The reproductive success of partridges (annual
values ranging between 1.2 and 3.4 young per adult) decreased through the
years 1987 to 2002. The annual survival rate of adult birds (annual values
ranging between 25 and 38%) did not show any signiﬁcant trends during the
monitoring period. The decrease of reproductive success and consequently
the observed population decline probably resulted mainly from increased
abundance of nest and hen predators, particularly red foxes.
Data on grey partridge (Perdix perdix) hunting bag in Poland have been collected
since the beginning of the 1960s. In the years 1960 through 1978 the annual hunting
bag varied widely from 62,000 to 744,000 birds, but no long-term declining tendency
was observed in this period. However, at the end of the 1980s, a considerable decrease
in the hunting bag was noted . A restriction of grey partridge hunting possibilities
was an incentive for hunters to implement actions to increase the number of these
birds on hunting grounds. The right selection of such actions required knowledge of
the factors affecting the situation of partridges. Therefore, detailed population studies
were carried out in the second half of the 1980s  and at the beginning of the
1990s the Polish Hunting Association initiated a grey partridge monitoring program
in order to provide current information about changes in their density in Poland and
the demographic mechanism causing such changes. The project is co-ordinated by
the Game Research Station of the Polish Hunting Association in Czempiń.
This paper presents methods and results of grey partridge monitoring in Poland, in
what concerns the range and changes in the hunting bag in the years 1981-2002 and
the basic demographic data (spring density, reproductive success and annual survival
rate) in the years 1987-2003.
Data on partridge hunting bag were obtained from annual reports provided by all
hunting districts leased by hunting clubs. The reports covered about 90% of hunting
districts in Poland. They were prepared after each hunting year (April-March) and
included, among other information, data on the hunting bag of all game animals
harvested during the previous year. The reports were sent to the Game Research
Station in Czempiń where they were processed and analysed.
Partridge populations were monitored on agricultural areas ranging in size from 50 to 150
km2, located in various parts of Poland. In the years 1987-1990 demographic data were
collected in three areas, and in the years 1991-1997 there were 12 permanent monitoring
areas. Since the year 1998 their number increased and varied between 19 and 41. The
monitoring areas were selected among hunting districts characterized by hunting bag of
partridges (thus probably also their density level), which allowed obtaining close to average
density values for a given region.
Spring counts of grey partridges were conducted and data about the composition of
their population in August were gathered to evaluate the reproductive success. The
spring density was estimated by call counts carried out from the 15th of March to
the 15th of April. The call counts were made in the morning or evening during good
weather conditions, at 10 points selected randomly on agricultural areas. Observers
arrived at the selected points before the expected period of most intensive partridge
calls (before sunrise or after sunset), and stayed there to the end of this period. The
number of males heard at the selected point was recorded. As the same individual
might be heard at several places, the principle of simultaneous identiﬁcation was
applied to distinguish between males, especially those heard close to one another
. The density of partridge pairs (D) was calculated according to the formula:
D = 1.45x1.16, where x is the mean number of males heard at the selected points .
In August, the records included information about the size and age composition of all
partridge coveys detected, integrating family groups or groups of adult birds without
brood . The annual number of observations registered in the whole country ranged
from 174 to 503. The ﬁeld work sessions were carried out by trained hunters.
The changes of average spring density of grey partridge in Poland were described
with an use of relative values, as the monitoring areas partially changed year by
year. The density value for the year 1998 (when there was an increase in the number
of monitoring areas) was assumed as 1, and the values for previous and subsequent
years were determined proportionally to the changes in the average density calculated
for areas where call counts took place in two consecutive years. Using August data,
the reproductive success of grey partridge in the country was calculated as the
young/adult ratio among all observed birds. The annual survival rate (S) of adult grey
partridges was calculated according to the formula: S = Dn+1/[Dn×(1+R)], where Dn
and Dn+1 are respectively relative densities for a given and subsequent spring, and R
is the reproductive success (, modiﬁed).
Temporal changes in partridge demographic variables were analyzed using simple
In the 1980s the annual hunting bag of grey partridge in Poland varied from 24,000
to 223,000 birds and the average value for this decade was 2.5 times lower than that
registered for both of the previous decades (Fig. 1). At the beginning of the 1980s
as well as in the late 1980s and in the early 1990s some increase was observed, and
consequently the hunting bag reached 293,000 individuals in the year 1992. However,
a subsequent continuous decrease was recorded and in the years 2000-2002 only
20,000-22,000 grey partridges were hunted in Poland (Fig. 1).
Fig. 1. Hunting bag of grey partridge in Poland in the years 1960-2002 (1960-1980 data were
available in ).
The relative spring density of grey partridge in Poland increased at the end of the
1980s and it was virtually stable at the beginning of the 1990s. However, in the
middle 1990s a considerable decrease was recorded. In the late 1990s the relative
density was about 3 times lower than that recorded at the beginning of the decade.
In the years 1998-2003, a slight increasing tendency was observed (Fig. 2). At the
beginning of the 1990s, the average spring densities ranged from 4.6 to 18.7 partridge
couples per km2 across permanent monitoring areas (n = 12), and at the beginning of
the 2000s, these values ranged from 0.5 to 10.5 couples per km2 (n = 34). Densities
in central and eastern Poland were higher than those noted in western, northern and
southern regions of the country (Fig. 3).
Fig. 2. Relative spring density of grey partridge population in Poland in the years 1987-2003
(the value for the year 1998 is assumed as 1).
Fig. 3. Average spring densities of grey partridge (pairs per km2) in individual monitoring
areas (n = 34) in Poland in the years 2000-2003.
The reproductive success of grey partridges in Poland in the years 1987-2002 varied
from 1.2 to 3.4 young per adult (Fig. 4A) and showed a signiﬁcant decreasing
tendency (r = - 0.531, df = 14, P = 0.03). The annual survival rate of adult partridges
ranged from 25% to 38% (Fig. 4B) and no signiﬁcant changes were found during the
study period (r = 0.248, df = 14, P = 0.4). The annual changes of the relative spring
density of partridges in the country were positively correlated with the reproductive
success (r = 0.834, df = 14, P < 0.001), but not with the annual survival rate of adult
birds (r = 0.461, df = 14, P = 0.07).
Fig. 4. Basic demographic variables of grey partridge population in Poland in the years 1987-
2002. A. reproductive success; B. annual survival rate of adult birds.
The results of grey partridge monitoring in Poland showed that the population decline
in the 1990s was connected with the decrease of reproductive success. According to a
more detailed analysis, the decline in the reproductive success was a result of changes
both in brood production rate and in chick survival rate .
The brood production rate in grey partridge depends on the availability of nesting
sites and on the abundance of nest and incubating hen predators . The second
factor seems to be the most important in Poland during the 1990s. In this decade the
number of foxes in the country increased considerably . It is possible that in this
period also the abundance of other predators increased, for example racoon dog and
mustelids, since their hunting bag in Poland increased signiﬁcantly . On the other
hand, radiotelemetry studies conducted in western Poland revealed that the main
cause of clutch and incubating female losses was predation by carnivores (81%),
mainly red foxes . Thus, the increased fox pressure during breeding season was
probably one of the main reasons or even the most important reason for the decrease
in partridge populations in Poland in the 1990s.
The major known phenomenon causing a long-term declining tendency of chick
survival rate in grey partridge is an intensiﬁcation of pesticide use . In Poland,
the use of pesticides per agricultural land unit decreased in the late 1980s and in the
early 1990s, but later an increase was noted and in the second half of the 1990s, the
pesticide use was 40% higher than in the ﬁrst half of the decade . This increase
may have been another reason for the decrease of reproductive success and for the
observed population decline.
According to the results of grey partridge monitoring in Poland, a project to improve
the situation of this bird in the country should be, ﬁrst of all, focused on measures that
would allow increasing partridge reproductive success, such as reducing the predation
pressure on nests and incubating females. The effectiveness of such measures have
been conﬁrmed experimentally elsewhere . In Poland, the control of common
predators operating during breeding season, especially red foxes, seems to be the
most relevant management measure towards partridge conservation.
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