Brown-headed cowbirds skew host offspring sex ratios

It's long been known that Brown-headed cowbirds, birds that like cuckoos lay eggs in the nests of other birds, reduce the number of offspring from a nest they parasitize. Now a recent report shows they also affect the sex of the host's offspring. Liana Zanette, Elizabeth MacDougall-Shakelton, (University of Western Ontario), Micheal Clinchy (University of Toronto at Scarborough) and James Smith (University of British Colombia, Vancouver) found the presence of cowbird chicks increase competition in the nests of Song Sparrows, with the sparrow's female chicks loosing out.

Shifts in open-ocean fish communities coinciding with the commencement of commercial fishing

Comparing data from a 1950's scientific survey with observations collected on longline fishing vessels, Peter Ward and Ransom Myers (Dalhousie University, Canada) found a major shift in the size and diversity of fish in areas of the tropical Pacific Ocean since the introduction of industrial fishing. Large predators such as sharks and large tuna declined in abundance an average of 21 percent, while the overall size of these animals also grew smaller. Smaller species, such as pelagic stingrays, increased in numbers.

Plant defense theory provides insight into interactions involving inbred plants and insect herbivores

Inbreeding is generally seen as detrimental, even for some self-fertilizing plants. Helen Hull-Sanders* and Micky Eubanks (University of Auburn) compared the reactions of inbred and non-inbred entire-leaf morning glory plants to various insects. The outbred, or cross-pollinated plants, were more resistant to generalized insect herbivores such as aphids while the self-fertilizing inbred plants fared better against leaf-chewing herbivores. This study is the first attempt
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Contact: Annie Drinkard
annie@esa.org
Ecological Society of America
15-Apr-2005