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19 Cards in this Set

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Cooperative Breeding
any situation where >2 individuals care for a clutch/litter of young
'helping behavior'
2 types
*Pair helped by greater than or equal to 1 non-reproductive helper
* more than 3 adults in a group all mate and all rear a clutch/litter of young
Benefits
* with mate sharing- some chance that helpers are caring for their own young (shared matings hypothesis)
* Helpers may be gaining experience at caring for young (experience hypothesis)
* helpers may be 'paying' for the right to remain in thier natal territory (payment to stay hypothesis)
* Helpers may be indirectly passing copies of their genes to future generations by helping close relatives (kin selection hypothesis)
* Helpers may be trying to impress possible future mates (mate attraction hypothesis)
CB in Australia
More common than in N hemisphere
-why?
* Unpredictable climate makes it difficult for young birds to breed
* have high survival rates, so vacancies are rare on territories sutible for breeding
Grey-crowned babblers –early work on cooperative breeding in Australia: experimental approach to determine whether helpers really do help
• Occur as pairs with
helpers (older offspring), up to 12 birds/group
• Insectivorous, feed mostly on ground
• Live in open eucalypt
woodlands
Control- left alone
Experimental- Removed all but one breeding pair, and one helper
Control- reared average amt (2.4) of fledgleings
Experimental- (.8)
Helpers did help- KIN selection hypothesis
Dusky moorhens (Gallinulatenebrosa) – cooperative breeding involving mate-sharing
• 1-4 adults of each sex in
each group
• All males usually mate
with all females –mating
system called polygynandry
• Females from a group lay
eggs in a joint clutch
• All adults incubate eggs
and care for young
• All group members jointly
defend their territory
Dusky moorhens are unusual
* Genetic polygynandry
Chicks raised in a single clutch can have multiple genetic mothers and fathers
* The adults within a group are not close relitives
Why they are polygynandrous
* Have very specific requirements for breeding
* Likely that only a fraction of the pln can get space for breeding territories
* Possible that larger groups are better able to defend breeding territories--> maybe Y unrelated indiv band 2gether
Why do they do it?
'Shared mating hypothesis'- all group members help b/c they might be mother or father of some of the offspring
NOT KIN selection hypothesis
Helping by juvenile dusky moorhens- only happens when a group has two successful clutches in the same season
Cooperative breeding in white-winged choughs (Corcoraxmelanorhamphos)
• Are obligate cooperative breeders – pairs without helpers can’t breed successfully
• Young birds of both sexes usually stay in their natal group, so group members are CLOSELY RELATED
• Are not reproductively mature until at least 4 years old
Why is reproductive maturity so late in choughs?
* It takes young several years to learn to feed themselves and nestlings efficiently
* This suggests that they wouldn't be able to breed succ before 4
Why does learning to feed take so long
* Young are fed for 4-8mo
* feed by searching soil and leaf litter for inverebrates- takes a while to learn
* Dig to 15cm deep
* In breeding season- choughs spend all say foraging
* unpredictable climate
* when not nesting, home ranges of groups can be 25km2
Helpers, do they help?
YES!
have higher repro sucess
More helpers= greater # of young that survive
Pairs of 2 or 3 never successful, can never pair up and breed
Why do helpers help (in choughs)
-Experience hypothesis: staying at natal groups and helping to raise young- learn about foraging and gain experience
-Kin Selection hypothesis: most helpers are closely related to the young theyre raising
-Payment to stay hypothesis: have to help if they want to stay in their group
Kidnapping
In territorial battles fledglings switch and live with other group
Helpers from the larger group attract fledglings
Why kidnapping?
- kidnapped young do well in new group
- at 15-20 birds they split into smaller groups. get to large size quicker
- provide helpers for new breeders in new smaller units
- stop inbreeding
Noisy miners (Manorinamelanocephala)
the extreme of cooperative breeding
• In the honeyeater family
• Eat primarily nectar and
insects
• Highly social species
• Unlike most other cooperative breeders, are
not territorial
• Each female has one mate, who is most likely to have
fathered her young, but young are also cared for by male helpers
• Nestlings are fed by up to
22 males; on average ~4
• Males help at multiple
females’ nests
Why do male noisy miners help at so many nests?
• Known that males in such a
community of noisy miners tend
to be close relatives, so some
degree of KIN SELECTION is
involved in helping behaviour
(kin selection hypothesis)
• if a female’s mate dies, she is likely to take the best helper at her nest as her new mate (mate attraction hypothesis)
Why do some species have helpers?
• If breeding vacancies in good territories are rare, young birds may have to delay their own breeding
• In this case, it is often safest for them to stay in their natal territory
• It may then be beneficial to them to help –either to gain
kin selection benefits, gain experience at rearing young,
or impress possible future mates
• In other cases, birds who can’t breed on their own share
mates