Birds
Week 9
Chris Foster
Migration and Dispersal
Residents; non-movers/ risky [cold winters] migrate at high latitudes.
Migration; regular seasonal movement between breeding and wintering grounds
- Artic Tern; 11,000 mile/ feeds en-route
- Risky; tradeoff with overwinter mortality
- Obligate; annual migrants [summer visits = swallow]
1. Survival; some die, but most survive = higher reproducing effort
2. Physiology; higher O2 intake/ diet to gain fat [50% body weight]/ need to increase
fat sources when they run out
3. Evolution; occurs in multiple orders, evolved independently.
a. Climatic change
b. Lac of needed resources
c. Seasonal interspecific dominance reactions
d. Seasonal intraspecific dominance reactions [forced out by other species]
e. Seasonal tracking, fruit/nectar.
4. Experiments;
- Emlen, 1966; measured Blackcap direction in orientation cage/ Blackcap from W.
Central Europe go SW// hybrids go south [selected against]
- Mechanisms in place but resident species = lower migratory anxiety.
Dispersal: movement between breeding sites [species range shift]
Philopatry; site faithfulness [breed and non-breed season] and stopover migration routes.
Local movement; within the territory/ home range
Nomadic/ Irruptive movement; usually some direction to random movement/ Boreal
species into residential areas.
Patterns of Migration;
- No always long distance round trips/ seasonal movements/ N-S/ Spring -autumn
- Vertical migration = altitudinal gradients
- Types;
1. Facultative; Blue tit, move
multiple times
2. Obligate; Robins, move
between 2 areas
3. Nomadism; not returning to home range
4. Partial Migration; not all individuals migrate / tufted duck spreads from core
range.
- Double breeding; N American Species = migrate N to breed/ migrate S to breed/
migrate to wintering grounds
- Altitudinal; issues with climate change
Week 9
Chris Foster
Migration and Dispersal
Residents; non-movers/ risky [cold winters] migrate at high latitudes.
Migration; regular seasonal movement between breeding and wintering grounds
- Artic Tern; 11,000 mile/ feeds en-route
- Risky; tradeoff with overwinter mortality
- Obligate; annual migrants [summer visits = swallow]
1. Survival; some die, but most survive = higher reproducing effort
2. Physiology; higher O2 intake/ diet to gain fat [50% body weight]/ need to increase
fat sources when they run out
3. Evolution; occurs in multiple orders, evolved independently.
a. Climatic change
b. Lac of needed resources
c. Seasonal interspecific dominance reactions
d. Seasonal intraspecific dominance reactions [forced out by other species]
e. Seasonal tracking, fruit/nectar.
4. Experiments;
- Emlen, 1966; measured Blackcap direction in orientation cage/ Blackcap from W.
Central Europe go SW// hybrids go south [selected against]
- Mechanisms in place but resident species = lower migratory anxiety.
Dispersal: movement between breeding sites [species range shift]
Philopatry; site faithfulness [breed and non-breed season] and stopover migration routes.
Local movement; within the territory/ home range
Nomadic/ Irruptive movement; usually some direction to random movement/ Boreal
species into residential areas.
Patterns of Migration;
- No always long distance round trips/ seasonal movements/ N-S/ Spring -autumn
- Vertical migration = altitudinal gradients
- Types;
1. Facultative; Blue tit, move
multiple times
2. Obligate; Robins, move
between 2 areas
3. Nomadism; not returning to home range
4. Partial Migration; not all individuals migrate / tufted duck spreads from core
range.
- Double breeding; N American Species = migrate N to breed/ migrate S to breed/
migrate to wintering grounds
- Altitudinal; issues with climate change
