If the biota in the course of eons, has built something we like but do not understand, then who but a fool would discard seemingly useless parts?
To keep every cog and wheel is the first precaution of intelligent tinkering
A. Leopold

Within a species, there is variation
• Ex. Morphology (size, shape, color), behavior
Some of this is linked to genetic variation
• Heritable
Different variations are better suited for certain conditions
• Those that are better suited for conditions do better (more food/different food; new nest sites, danger avoidance, etc…)
• When this variation is heritable, it is passed on to offspring and, if conditions remain the same, they gain an advantage.

• Mutation – errors
– Most are harmful or neutral
• Gene flow – migration followed by breeding
– Add new alleles to population pool or change frequencies of alleles present
• Genetic drift – chance alterations in small populations
– bottlenecks and founder effects
• Accumulates over time

• Individuals within populations are variable for nearly all traits
• Individuals pass on their genes to offspring
• More offspring are produced than can survive
• Individuals that survive and go on to reproduce (the most) are those with the varieties (alleles) that best adapt them to their environment
•
Outcome: alleles associated with higher fitness increase in frequency from one generation to the next

• Any cumulative change in the characteristics of organisms or populations from generation to generation
• Evolutionary agents
– Mutation
– Gene flow
– Genetic drift
– Natural selection

C. Darwin

• Losing large numbers of animals, can lose variation as well
• May limit individual’s ability to persist under current conditions
• Or future conditions . . .

What is a population?
• a group of organisms of the same species occupying a defined area (habitat patch) at the same time
Ostrich in the savannahs of the Loeli area, Sudan. Photo by Paul Elkan ©2007 Nat. Geo./ WCS

Density: amount per unit area (hectare, square kilometer, etc.)
Example: 7 frogs/hectare (ha)
100 m
100 m
(1 ha = 10,000 m 2 = 0.01 km 2 = 2.5 ac)

Niche: an n-dimensional hypervolume which includes the range of biological and physical conditions under which an organism can exist, including the resources that an animal must exploit for growth and reproduction
A portion of the feeding niche of the Blue-gray
Gnatcatcher
(Smith & Smith 1998)
Prey length (mm)

Population size:
N t
= population size at time t
N t+1
= population size at time t+1
N t+1
= N t
+ Births + Immigration – Deaths -Emigration
Growth rates: r = exponential growth rate
λ (‘lambda’) = intrinsic population growth rate

Reproduction, births, natality (B)
Immigration (I) Population
Emigration (E)
Mortality, death (D)

Study Area
From 1999 to 2007, we studied songbird communities and populations within forest patches from
3 landscape types:
•Forest reserves (5)
•Developed
Subdivisions (9)
•Changing landscapes (13)

Developed sites are older residential areas built prior to the onset of study.
Reserve sites are primarily forested.
Changing sites are undergoing residential development during the study

Closed System: r = (b - d) r = actual growth rate of population b = birth rate d = death rate
Open System: r = (b - d) + (i - e) i = immigration e = emigration

Reproduction, births, natality (B)
Immigration (I) Population
Emigration (E)
Mortality, death (D)

• Length of gestation or incubation period & reproductive rate
• Sex ratios
• Breeding system (monogamous or polygamous)
• # of females that breed at each age
• # of young per female of various ages
• Influence of nutrition on reproduction

r-selected species (fast species) :
• shorter gestation period
• reproduce more frequently
• produce many offspring at a time
K-selected species (slow species):
• longer gestation period
• reproduce less frequently
• produce few offspring at a time

• Length of gestation or incubation period & reproductive rate
• Sex ratios
• Breeding system (monogamous or polygamous)
• # of females that breed at each age
• # of young per female of various ages
• Influence of nutrition on reproduction

1. Monogamy
– Seasonal: same mate only for 1 year
Canvasbacks
– Lifetime: same mate for life
Bald Eagles

2. Polygamy
- polyandry : one female mates with several males
Red Phalaropes
- polygyny : one male mates with several females
Fur Seals

3.
Promiscuity: no pair bonds

• Length of gestation or incubation period & reproductive rate
• Sex ratios
• Breeding system (monogamous or polygamous)
• # of females that breed at each age
• # of young per female of various ages
• Influence of nutrition on reproduction

A fecundity schedule for Chamois from New Zealand.
3
4
1
2
5
Age (yrs) N # Female births per pregnant female
_____________________________________________
0 0.000
60
36
70
48
26
2
14
52
45
19
0.017
0.194
0.371
0.469
0.365
6
7
19 16
6 5
0.421
0.417
>7 10 7 0.350
___________________________________________

Monitoring Songbird Productivity
Productivity---Territory success and estimates of fledglings produced via spot mapping and nest monitoring.
Monitored and color-banded individuals of 7 species:
# Colorbanded
Individuals
# Territories/Nests
Monitored
American Robin 289 375
Bewick’s Wren
160 210
Dark-eyed Junco
Song Sparrow
Spotted Towhee
Swainson’s Thrush
Winter Wren
141
1177
533
647
195
339
867
848
433
552

Landscape specific productivity estimates :
From spot-mapping data and nest monitoring
Territory success rates
Number of fledglings/ successful nest
We used these numbers to get estimate of fecundity
(number of young produced per female/year)
Reserves Changing Developed
Song Sparrow
% Successful 61.2 70.6
64.4
% 2 nd Brood
Fledglings/nest attempt
Fledgling/female
7.5
1.56
0.78
16.4
2.00
1.00
0.16
2.14
1.07
From Oleyar et al. (in prep)

Landscape Species
Developed American Robin
Bewick's Wren
Dark-eyed Junco
Song Sparrow
Spotted Towhee
Swainson's Thrush
Winter Wren
Fecundity
0.59
0.92
1.37
1.13
0.57
0.40
1.23
var
0.08
0.88
0.15
0.46
0.12
0.07
0.08
Changing American Robin
Bewick's Wren
Dark-eyed Junco
Song Sparrow
Spotted Towhee
Swainson's Thrush
Winter Wren
0.89
0.78
1.10
1.23
0.82
0.40
0.61
Reserve American Robin
Bewick's Wren
Dark-eyed Junco
Song Sparrow
Spotted Towhee
0.80
0.84
0.55
0.81
0.74
0.13
0.16
0.50
0.37
0.15
Swainson's Thrush 0.50
0.06
Winter Wren 0.61
0.09
* Upper 95% CI Limit of parameters used for calculating λ
** Changing Juv survival estimate used in calculating λ
0.16
1.33
0.38
0.21
0.46
0.07
0.33
0.55
0.32
0.47
0.54
0.55
0.53
0.38
0.71
0.14
0.5
0.51
0.54
0.59
0.54
Adult
0.4
0.29
0.5
0.54
0.5
0.46
0.35
Apparent Survival se Juv
0.15
0.14
0.17
0.03
0.06
0.07
0.19
0.13
0.08
**
0.21
0.18
0.16
0.11
se
0.08
0.05
0.04
0.05
0.05
0.08
0.12
0.08
0.09
0.02
0.03
0.04
0.08
0.22
0.06
0.17
0.06
0.06
0.1
0.12
0.18
0.08
0.14
0.18
0.18
0.17
0.1
0.31
0.03
0.15
0.16
0.18
0.21
0.18
0.08
0.03
0.05
0.03
0.03
0.04
0.03
0.23
0.02
0.09
0.04
0.04
0.08
0.08
λ
0.5416
0.4526
0.7543
0.827
0.6563
0.5719
0.5823
Upper λ *
0.962
0.9243
1.158
1.022
0.8795
0.7886
1.207
0.7606
0.4566
0.6924
0.8125
0.7475
0.6368
0.5016
1.102
0.7325
0.9812
0.9273
0.9013
0.7744
0.7522
0.9666
0.2435
0.6308
0.6962
0.724
0.7332
0.6974
1.443
0.4885
1.176
0.9349
0.9245
0.9873
1.057
From Oleyar et al. (in prep)

• Length of gestation or incubation period & reproductive rate
• Sex ratios
• Breeding system (monogamous or polygamous)
• # of females that breed at each age
• # of young per female of various ages
• Influence of nutrition on reproduction

Reindeer
(caribou)
# young produced
Bighorn sheep
Population density (top) or size (bottom)

Reproduction, births, natality (B)
Immigration (I) Population
Emigration (E)
Mortality, death (D)

Survivors (l x
) females males
2 4 6 8 10 12 14 16 18 20
Age at Death (years)

Estimating survival in different landscapes:
Mark and recapture:
Capture, mark, and release individuals in a population.
Recapture or re-sight individuals at regular intervals
(yearly)
From this can estimate apparent survivorship and encounter rates.
Photo by T. Unfried

Estimating survival in different landscapes:
Yearly encounter histories based on recapture and resighting of colorbanded individuals.
Encounter history: series of 0’s and 1’s denoting whether animal was seen during year or not.
100000 : marked and never seen again
101001 : marked and recaptured/resighted in yr 3 and 6
111111 : marked and recaptured/resighted in every yr
Photo by T. Unfried

Landscape Species
Developed American Robin
Bewick's Wren
Dark-eyed Junco
Song Sparrow
Spotted Towhee
Swainson's Thrush
Winter Wren
Fecundity
0.59
0.92
1.37
1.13
0.57
0.40
1.23
var
0.08
0.88
0.15
0.46
0.12
0.07
0.08
Changing American Robin
Bewick's Wren
Dark-eyed Junco
Song Sparrow
Spotted Towhee
Swainson's Thrush
Winter Wren
0.89
0.78
1.10
1.23
0.82
0.40
0.61
Reserve American Robin
Bewick's Wren
Dark-eyed Junco
Song Sparrow
Spotted Towhee
0.80
0.84
0.55
0.81
0.74
0.13
0.16
0.50
0.37
0.15
Swainson's Thrush 0.50
0.06
Winter Wren 0.61
0.09
* Upper 95% CI Limit of parameters used for calculating λ
** Changing Juv survival estimate used in calculating λ
0.16
1.33
0.38
0.21
0.46
0.07
0.33
0.55
0.32
0.47
0.54
0.55
0.53
0.38
0.71
0.14
0.5
0.51
0.54
0.59
0.54
Adult
0.4
0.29
0.5
0.54
0.5
0.46
0.35
Apparent Survival se Juv
0.15
0.14
0.17
0.03
0.06
0.07
0.19
0.13
0.08
**
0.21
0.18
0.16
0.11
se
0.08
0.05
0.04
0.05
0.05
0.08
0.12
0.08
0.09
0.02
0.03
0.04
0.08
0.22
0.06
0.17
0.06
0.06
0.1
0.12
0.18
0.08
0.14
0.18
0.18
0.17
0.1
0.31
0.03
0.15
0.16
0.18
0.21
0.18
0.08
0.03
0.05
0.03
0.03
0.04
0.03
0.23
0.02
0.09
0.04
0.04
0.08
0.08
λ
0.5416
0.4526
0.7543
0.827
0.6563
0.5719
0.5823
Upper λ *
0.962
0.9243
1.158
1.022
0.8795
0.7886
1.207
0.7606
0.4566
0.6924
0.8125
0.7475
0.6368
0.5016
1.102
0.7325
0.9812
0.9273
0.9013
0.7744
0.7522
0.9666
0.2435
0.6308
0.6962
0.724
0.7332
0.6974
1.443
0.4885
1.176
0.9349
0.9245
0.9873
1.057
From Oleyar et al. (in prep)

0.6
0.4
0.2
0.0
1.0
0.8
WIWR
Adult
Juvenile
Reserve Changing Developed
Winter Wren
0.4
0.2
1.0
SWTH
0.8
0.6
Adult
Juvenile
0.0
Reserve Changing Developed
Swainson’s Thrush
1.0
AMRO
0.8
0.6
0.4
0.2
Adult
Juvenile
0.0
Reserve Changing Developed
American Robin
From Oleyar et al. (in prep)

0.6
0.4
0.2
0.0
1.0
0.8
SOSP
Adult
Juvenile
Reserve Changing Developed
0.4
0.2
0.0
1.0
0.8
0.6
SPTO
Adult
Juvenile
Reserve Changing Developed

Reproduction, births, natality (B)
Immigration (I) Population
Emigration (E)
Mortality, death (D)

• Juvenile dispersal: movement from place of birth to place of breeding
• Breeding dispersal: movement by adults from one place of breeding to another
– Birds: Female dispersing sex
– Mammals: Male dispersing sex

0
#
#
#
# #
#
American Robin post-fledging movements
#
#
#
#
#
#
500
#
#
#
#
#
#
#
#
#
#
#
#
#
1000 1500 2000 2500
#
#
#
#
#
#
#
#
#
#
# #
##
#
3000
#
3500 4000 Meters

Adult survival, juvenile survival, and fecundity are what we need to estimate λ, the intrinsic population growth rate.
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Winter Wren
Reserve Changing Developed
Source/ growing populations
Stable population
Sink / declining

Landscape Species
Developed American Robin
Bewick's Wren
Dark-eyed Junco
Song Sparrow
Spotted Towhee
Swainson's Thrush
Winter Wren
Fecundity
0.59
0.92
1.37
1.13
0.57
0.40
1.23
var
0.08
0.88
0.15
0.46
0.12
0.07
0.08
Changing American Robin
Bewick's Wren
Dark-eyed Junco
Song Sparrow
Spotted Towhee
Swainson's Thrush
Winter Wren
0.89
0.78
1.10
1.23
0.82
0.40
0.61
Reserve American Robin
Bewick's Wren
Dark-eyed Junco
Song Sparrow
Spotted Towhee
0.80
0.84
0.55
0.81
0.74
0.13
0.16
0.50
0.37
0.15
Swainson's Thrush 0.50
0.06
Winter Wren 0.61
0.09
* Upper 95% CI Limit of parameters used for calculating λ
** Changing Juv survival estimate used in calculating λ
0.16
1.33
0.38
0.21
0.46
0.07
0.33
0.55
0.32
0.47
0.54
0.55
0.53
0.38
0.71
0.14
0.5
0.51
0.54
0.59
0.54
Adult
0.4
0.29
0.5
0.54
0.5
0.46
0.35
Apparent Survival se Juv
0.15
0.14
0.17
0.03
0.06
0.07
0.19
0.13
0.08
**
0.21
0.18
0.16
0.11
se
0.08
0.05
0.04
0.05
0.05
0.08
0.12
0.08
0.09
0.02
0.03
0.04
0.08
0.22
0.06
0.17
0.06
0.06
0.1
0.12
0.18
0.08
0.14
0.18
0.18
0.17
0.1
0.31
0.03
0.15
0.16
0.18
0.21
0.18
0.08
0.03
0.05
0.03
0.03
0.04
0.03
0.23
0.02
0.09
0.04
0.04
0.08
0.08
λ
0.5416
0.4526
0.7543
0.827
0.6563
0.5719
0.5823
Upper λ *
0.962
0.9243
1.158
1.022
0.8795
0.7886
1.207
0.7606
0.4566
0.6924
0.8125
0.7475
0.6368
0.5016
1.102
0.7325
0.9812
0.9273
0.9013
0.7744
0.7522
0.9666
0.2435
0.6308
0.6962
0.724
0.7332
0.6974
1.443
0.4885
1.176
0.9349
0.9245
0.9873
1.057
From Oleyar et al. (in prep)

1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Song Sparrow
Reserve Changing Developed
No obvious response in growth rate by landscape.
1.0
0.8
0.6
0.4
0.2
0.0
1.8
1.6
1.4
1.2
Spotted Towhee
Reserve Changing Developed

1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Winter Wren
Reserve Changing Developed
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
American Robin
Reserve Changing Developed
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Swainson's Thrush
Reserve Changing Developed
Declining λ outside of reserves?

1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Dark-eyed Junco
Reserve Changing Developed
Possible sink during development for some species followed by recovery as subdivision ages?
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Bewick's Wren
Reserve Changing Developed

How do these projections match up with what we see out there?
•Winter Wren numbers high and
‘stable’ in reserves, low and/or declining elsewhere
•Robin numbers ‘stable’ but low in reserves, highest in developed residential areas
•Are developed landscapes ecological traps for Robins?
2.0
Reserves
1.5
1.0
0.5
1.0
0.5
0.0
0.0
2.0
Changing
1.5
Winter Wren
American Robin
Swainson's Thrush
2.0
Developed
1.5
1.0
0.5
0.0
1999 2000 2001 2002 2003
Year
2004 2005 2006 2007

• Density dependent factors
– Ex: Predation, competition, habitat availability
– change population growth in predictable ways
– N is driven by population density
• Density independent factors
– Random or
Stochastic events
– Ex. Weather, accidents
– Breeding
14 aug 2007

• Population regulation : the tendency of population sizes to stay within a certain range
# of
Animals
(N) time

# of
Animals
(N) k
Carrying capacity (k): the number of organisms that can be supported by a given area; the actual number of organisms fluctuates near this time

Carrying capacity (k) k
N N time
Classic growth curve, unlimited resources time
Classic growth curve, limited resources (k)

Example of unlimited growth:
Australian rabbit (European hare)
• 1859: 24 hares introduced (for human food?)
• 1865: over 20,000 hares were harvested, actual population much greater.
• Mid-1800’s to mid-1900’s: major problem with too many hares; caused habitat destruction and reduction in native mammals
• 2000: still present, local problems

Rabbits exceeded k No rabbits
Rabbit-proof fence

High food addition
Townsend’s vole
Low food addition
No food added
Shaded area is winter

Population cycles: Ex. peaks in lynx populations show time lag behind peaks in snowshoe hare populations
Snowshoe hare
Lynx
Time (years)

• Competition – demand by 2 or more individuals of the same or different species for a common resource
• Between 2 individuals of same species:
Intraspecific
• Between 2 individuals of different species:
Interspecific
• Limited supply of resource:
Exploitation
• Not limited but interaction detrimental:
Interference

Inter- or Intraspecific competition?
Exploitation or Interference competition?