Lecture 13 - accentor mating systems

Question 1

what mating systems do dunnocks exhibit?

Answer 1

polygyny, polyandry, monogamy, and polygynandry

Question 2

what mating systems do alpine accentors exhibit?

Answer 2

always polygynandrous

Question 3

what is the ecological basis for mating systems

Answer 3

The variation in mating systems observed within and between species is related to the distribution of resources in the environment. This determines female ranges, which in turn determine male ranges

Question 4

describe dunnock mating systems

Answer 4

Females defend exclusive territories against other females

Question 5

what causes the emerging dunnock mating system?

Answer 5

depends on the ability of males to monopolise territories, i.e. female territories are the template for male distribution

Question 6

describe the territory of polygynous or monogamous female dunnocks

Answer 6

have small territories defendable by one male

Question 7

describe the territory of polyandrous and polygynandrous female dunnocks

Answer 7

have larger territories where a single male (= alpha male) is unable to prevent a second male (= beta male) from settling

Question 8

which male is dominant alpha or beta?

Answer 8

alpha males

Question 9

what are dunnock female territory size affected by?

Answer 9

was influenced by food availability

- ‘Fed’ females were less likely to be polyandrous than ‘unfed’ females

Question 10

describe polygynandry in dunnocks

Answer 10

normally 2 males and 2 females

Question 11

what effects mating systems?

Answer 11

Male and female dispersion

Question 12

Need to show the size of female range in dunnocks is a function of resource availability and that it also effects the mating system - how?

Answer 12

do an experiment

Question 13

describe the mating systems of alpine accentors

Answer 13

• All alpine accentors are polygynandrous

Question 14

describe the territories of alpine accentors

Answer 14

• typically 3 females and 3 males in one territory

- Females have relatively enormous overlapping ranges

Question 15

why do accentors have large ranges?

Answer 15

large ranges are necessary to exploit the spatially and temporally patchy invertebrate prey blown up from the valley

Question 16

why can dunnocks defend individual females but accentors cant?

Answer 16

At lower altitudes (where dunnocks live), food is more abundant and predictable. Because of their range size, individual males are unable to defend single females whereas in accentorstwo to four males share a large undefended range (18 ha) encompassing the ranges of two to four females, hence polygynandry is the norm in this species

Question 17

describe paternity and parental care in accentors and dunnocks

Answer 17

In both species, males compete with each other in order to maximise their mating success, and then subsequently provide parental care in relation to their paternity

Question 18

what is typical accentor and dunnock breeding biology?

Answer 18

• Female builds nest
• Lays 3-5 blue eggs
• Female incubates
• Both sexes feed chicks and fledglings
• Pair often have 2 broods per year

Question 19

describe monogomy in dunnocks

Answer 19

• Male guards female
• Female solicits
• Male pecks cloaca, female ejects sperm from earlier matings
• Copulate 1-2 times an hour throughout the day for about 10 days
• Male monopolises matings gaining 100% paternity. Male provides c.50% of nestling care

Question 20

describe polygyny in dunnocks

Answer 20

• Polygynous males guard and copulate with two females
• If the male is lucky the females are fertile asynchronously but if not he has to try and shuttle back and forth
• Males either invest in brood of one female but not the other, or they divide their investment between the two
• on average females get less care than a monogamous female would
• males gain 100% paternity

Question 21

describe polyandry in dunnocks

Answer 21

With two males on a territory, there is intense competition among males for matings. Alpha male may gain all matings but beta male often obtains some (up to 50%), so paternity may be shared. Paternal care is related to paternity share, estimated from their share of copulations

Question 22

describe care and mating success in accentors

Answer 22

similar to dunnocks - paternity is often shared among males and paternal care is again related to mating share and hence paternity

Question 23

what were the results from the experiment to show that feeding in male dunnocks depends on mating and not other factors?

Answer 23

• males removed temporarily, giving
• males increased share of mating’s
• As predicted the beta males work harder the more access to mating they had
• Care by males is casually affected by mating success

Question 24

describe competition among female dunnocks?

Answer 24

• Scraps between females are seen to stop the mating so they can monopolise care from a male
• Desertion follows fights by females
• Desertion rates are significantly higher in polygyny than polyandry

Question 25

how do polyandrous dunnock females aim to mate?

Answer 25

should copulate with both males in her group to gain their parental investment and should aim for 50:50 share of matings with α and β
If successful, both males subsequently help to feed her brood

Question 26

describe female competition between alpine accentors

Answer 26

• To convince males they have some paternity females copulate up to 1,000 times per clutch
• Males have huge testes-
• females advertise their fertility by either revealing their bright red cloaca or singing to attract males

Question 27

why is the female singing in alpine accentors unique and why is it done?

Answer 27

• unusual in birds to have female song - trick to maximise paternal care of brood

Question 28

what effect does male parental care have on dunnocks?

Answer 28

• paternal care is critical for female reproductive success females do worst in polygyny where they have to share a male with another female, and
  they do best in polyandry where both males help to feed her brood. Intermediate success is achieved in monogamy. By contrast, males do best in
  polygyny because although each female has lower success, together they produce more young then in monogamy. Males do worst of all in polyandrous
  systems where females copulate with both males because although more young are produced, paternity is shared between the two males