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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
* 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
* 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
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?
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
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
• 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