NYTIMES:
Throughout the day, possible culprits — among them a minor gas leak in Greenwich Village and natural-gas pipelines in northeastern New Jersey — were considered and ruled out.
The olfactory mystery in the New York region was matched by strange activity elsewhere. In Austin, Tex., police cordoned off 10 blocks of the downtown business district early yesterday after more than 60 birds were found dead overnight along Congress Avenue, which leads to the State Capitol. Air testing there failed to find a cause, but preliminary results determined that people were not at risk.