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Rhea findings.

Two papers in Journal of Field Ornithology 69(1) worth looking at because
ratites are excellent non-avian dinosaur analogues (the best!).

1.  Orphan eggs--single eggs oviposited far from the active nest--are
They may be placed in an incubator and hatched.  Good for increasing
productivity of wild populations.

As I've noted before (pardon repeat), at least two hypotheses for this:
abundant food on pampas leads to over-production; and, orphan eggs are
Does anyone know how common this behavior is?

2.  Adoption of unrelated orphan chicks.  23% of adult males did this.
Chicks usually < 1 wk. old.   Interesting fact: in this study the adopted
chicks experienced higher survival rates than the related chicks.

This behavior also occurs in ostriches: it might have been common in
non-avian dinosaurs.
Hypotheses include: dilution of predation risk for ones own chicks; high
gain for adoptees/no penalty for adopter (chicks feed selves) leads to
asymmetry favoring behavior--parental commensalism.

My burning question: what is it about large egg layers in particular that
favors this behavior (assuming it's not primitive ratite trait).