In another post I described finding large numbers of cicada wings  
detached from bodies during a hatch of periodical cicadas in  
Lawrence, Ks.  I surmised that the predator had been bats.  But  
today, before the snow plow came, I searched the internet for other  
possibilities. Bob Fisher had written me about predator satiation  
(thanks, Bob), and interestingly, the source I found is from a paper  
by Richard Karban at University of Pennsylvania, INCREASED  
PERIODICAL CICADAS.  Ecology  1982 Ecological Society of America

I do not have access to the entire paper.

Note the sentence I've isolated from the rest of the abstract.  I've  
quoted the rest  because I was interested in the conclusions that the  
sheer number of cicadas exceeds the capacity of predators to eat  
them, and that total predation is related to density of predators not  
to density of cicadas.  That helps explain the evolution of huge,  
periodic numbers.

> Abstract The reproductive success of periodical cicadas, measured  
> as the number of offspring produced per adult, is found to increase  
> as adult density increases. The inverse density-dependent pattern  
> at the adult stage occurred over the entire range of adult  
> densities encountered. This result could have been caused by (1)  
> predator satiation, (2) increased fecundity at higher densities,  
> (3) more efficient mating at higher densities, and (4) movement of  
> adults from sites of low initial densities to sites of high  
> densities. The hypothesis of predator satiation was explored in depth.
> Predation at each site was crudely estimated by collecting cicada  
> wings, which are discarded by avian predators.
> If predator satiation accounts for the inverse density-dependent  
> mortality, then each cicada's risk of capture will decrease as  
> cicada density increases. The data suggest that this prediction is  
> true; predation did not increase as cicada density increased so  
> that the probability of escaping predation is greater at high- 
> density sites. Estimated predator densities are independent of  
> cicada densities, which indicates that predators cannot respond  
> numerically to the cicada emergence. As cicada density increases,  
> the number of cicada wings recovered per bird does not  
> significantly increase, suggesting that birds are satiated.  
> Significantly more cicada wings were recovered at sites with more  
> birds. Total cicada predation was independent of cicada density but  
> dependent on the density of predators. Some evolutionary  
> consequences of these results are discussed.

So I'm imagining birds discarding the wings as they might the shell  
of a sunflower seed.  Another paper about a Brown Hawk Owl in Taiwan  
observes that it discards insect wings and other hard parts.  (http://

June Newman
Carrollton, MO


The Audubon Society of Missouri's Wild Bird Discussion Forum
ASM Fall Meeting: September 24-26 at Camp Clover Point