XXIII. Brood Parasites (No Chapter) 2011
A.
Definition
1.
Organisms that live in the nest or egg mass of a host species
2.
Brood parasite benefits from association at a cost to host species
3.
Some brood parasites may completely destroy all of the offspring of the
host species and in such cases may have an ecological impact similar to
that of parasitic castrators
B.
Bird-nest Parasitism
1.
Bluebirds
a.
Some (not all) females will lay eggs in nests of other bluebirds
(1)
Occurs when nest unguarded
(2)
Hatchlings raised by Afoster@ parents
b.
Benefit: Female Acheater@ or Aparasite@ produces offspring at
minimal cost in caring for young
c.
Cost
(1)
AParasite@ female must watch other nest to take advantage
of unguarded periods
(2)
AParasite@ female is not guarding her own nest.
(3)
Poetic justice: Parasitic females apparently are more likely
to end up caring for offspring of other Aparasitic@ females
than Anon-cheaters@.
2.
Cowbirds or cuckoos
a.
Young are always raised by foster-parent birds
(1)
Over 200 species of foster birds
(2)
Cowbird eggs hatch sooner than host species
(3)
Young of foster-parents are out-competed and do not
survive
b.
There is concern that brood parasitism by cowbirds is pushing
some species of song birds toward extinction.
c.
Female cowbirds prefer wooded edges and small woodlots for
finding host nests
d.
Cowbird numbers have recently increased greatly due to forest
fragmentation among other factors
C.
Insect-nest parasitism
1.
Cuckoo wasps
a.
Parasitic queen invades hive of a host species
b.
Kills queen of host species
c.
Eggs laid by parasitic queen species are cared for by host workers
d.
Eventually host species is replaced by cuckoo wasp species
2.
Ants
a.
Life-cycle of free-living ants
(1)
New queen leaves nest and mates with male (often in the
air)
(2)
Digs or builds a simple nest
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(a)
(b)
b.
c.
d.
e.
Lays eggs
Eggs hatch into sterile females that dig nest, forage,
and tend queen
(c)
Odor identifies members of colony
Cleptobiosis (Greek = steal)
(1)
Ants (small species) build nest close to large-sized forager
ants
(2)
Small species feeds on refuse of other colony or robs
workers of other colony
Lestobiosis (Greek = robber)
(1)
Stay in walls of large nests of other ants & termites
(2)
Steal food and prey on inhabitants
Teleutomyrmex schneideri the ultimate social parasite
(1)
Only occurs in nests of its host species
(2)
Queens
(a)
Produce no workers
(b)
Ride on the back of the host queen
(c)
Fed by workers of host species
(3)
Eggs, cocoons & males of parasite cared for by host
workers
Slave-makers Araid@ nest of another species
(1)
Carry-off cocoons
(2)
Slaves hatch and work in nest of raider
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