POPULATION REGULATION, FLUCTUATION, AND COMPETITION WITHIN SPECIES 119
0.2
0
- 0.2
0.6
Winter mortality 0.2
2.0 3.0 3.4 3.8
Log of juveniles in winter Log of hatching population
Chick mortality
Fig. 8.9Examples of (a) Great tit (b) Partridge
density-dependent mortality
in birds. (a) Great tit (Parus
major) overwinter mortality
(log of [juveniles in
winter/first year breeding
population]) plotted against
log juvenile density in
winter. (After McCleery and
Perrins 1985.) (b) Chick
mortality of European
partridge (Perdix perdix)
(measured as log hatching
population/ log population
at 6 weeks) plotted against
log hatching population, in
Hampshire, England. (After
Blank et al. 1967.)
80
60
40
20
0
80
70
60
50
40
30
20
10
0
100
80
60
40
20
0
(a)
Male
Female
60 100 140 180
Female population size (numbers)
(b)
0246810121416182022242628
Reindeer density in winter
(numbers / winter habitat area)
(c)
200 250 300 350 400 450 500 550
Study population size (number of sheep)
Lambing at 12 months (%)
Calves / 100 females
≥ 1 year old
Juvenile mortality (%)
Fig. 8.10Density dependence in large mammals. (a) Juvenile mortality of male and female red deer on the island of Rhum,
Scotland. (After Clutton-Brock et al. 1985.) (b) Juvenile recruitment per 100 female reindeer older than 1 year in Norway.
(After Skogland 1985.) (c) The fertility rate of 1-year-old Soay sheep on St Kilda island. (After Clutton-Brock et al. 1991.)