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nest parasitism, parental care and such



Hi.  This is my first intrusion into the system so please pardon any rough 
edges.  

There have been several bird-related topics on which I might comment.

1)  Nest parasitism.  Australia has 12 species of parasitic cuckoos (no 
cowbirds!) ranging from cowbird-size to crow-size.  Their approaches to the 
initial infiltration of a host species? nest vary among (a) laying their egg 
with those of the host and let the young cuckoo take over and push out the host 
eggs/chicks, (b) removing (throw out or eat) the eggs of the host before 
laying, or (c) removing (throw out or eat) the chicks of the host before 
laying.  Because Australia does not have the strict seasonality of the Northern 
Hemisphere, it is possible for the host species to successfully raise several 
broods during the year.  Most of the cuckoos are migratory and arrive after the 
first host clutch is underway, which is generally too far advanced to attempt 
to parasitise.  The cuckoos claim the next clutch, and the host gets any 
subsequent ones. 

One characteristic of the host-parasite relationship (at least among the 
Australian cuckoos) is that the parasite is virtually always a larger animal 
than the host species.  If the possibility of nest parasitism existed among 
dinosaurs, then this size relationship may offer a clue to its existence when 
examining the relative size of the putative host-parasite species.

The comment about an African cuckoo that killed the hosts eggs/chicks with a 
hook on the bill was referring to the honeyguides, the Indicatoridae, a 
woodpecker relative.

2) Parental care.  The cuckoos, cowbirds and other parasitic birds do not 
qualify as the eggs do receive parental care (albeit not their own parents) and 
there is evidence that the true parents (in some Australian cuckoos at least) 
monitor their well being.  One group of birds that does have a highly developed 
pattern of laying the eggs and leaving them to hatch unattended is the 
Megapodiidae (megapodes, mound-building birds, incubator birds) of the 
Australasian region.  The eggs are placed in a mound of decaying vegetation, 
volcanically active soil, etc and the heat from that source incubates the eggs. 
 There is no parental attention following the laying of the eggs.  Any young in 
the way of an adult tending the nesting area is treated like a rock or stick 
and kicked out of the way.

The young hatch in a hyper-precocial state.  They must dig out of the nesting 
around without assistance, sometimes from a depth of several feet.  Chicks must 
be self-sufficient from hatching and are able to fly within a few hours of 
emerging from the nest mound or chamber.

3) Cooperative hunting.  There is evidence of cooperative hunting in the 
Wedge-tailed Eagle _Aquila audax_.  Usually this occurs in pairs, but there is 
one record of 15 birds working together to wear down a kangaroo.  Two birds 
would harry the prey for a while and then be replaced by two others from the 
birds flying above.  Cooperative hunting has also been reported for the Brown 
Falcon  _Falco berigora_.

LL