| Abstrakt: |
Until the late 1960s, Northern Goshawks, Accipiter gentilis atricapillus, were considered rare breeders in Wisconsin. Research initiated in 1971 revealed a small but growing breeding population, which continued to increase until the mid 1990s when depredations by mammalian predators began to reduce numbers. Since 1985, reproduction has fallenbelow the estimated threshold of 1.7 young fledged/active nest needed to maintain a stable population. The reintroduced Fisher, Martes pennanti, is largely responsible for increased nest failure and adult female mortality, with the turnover rate of nesting females having doubled to over 40%. Twenty-two years of reproductive data reveal a correlation between population levels and the 10-year wildlife cycle. Thegoshawk has been listed as a 'sensitive species' since 1986 in the Nicolet National Forest, and guidelines have been established for nestsite protection. However. no such standards exist for state, county and private lands, where populations are declining. Legal and illegal'take' of nestling goshawks is a continuing concern, especially as nest sites under national forest management become more vulnerable to falconers, who have taken an estimated 5% of young from monitored nests. [ABSTRACT FROM AUTHOR] |
