Northern bobwhite (Colinus virginianus) COSEWIC status report: chapter 8

Limiting Factors and Threats

As outlined in the Habitat Trends section, habitat loss is probably the most significant cause of the observed decline in Northern Bobwhite populations in Canada.  Shrinking habitat blocks may become no longer suitable for the continued existence of bobwhite.  Given the fragmented nature of much of the available habitat in southwestern Ontario, it is entirely likely that small isolated groups will continue to disappear. The relative size of a population is a primary factor promoting local extinctions (Bolger et al. 1991).

But, at the same time, might the disappearance have been influenced by the dilution of the native gene pool by released birds of unknown origin, not well adapted to Canadian winters and habitats? Northern Bobwhite are raised commercially for restocking purposes and for specialty restaurant menus.  Prior to the passing of the Wildlife Conservation Act in Ontario in 1997, it was apparently possible for most anyone to get eggs, incubate them, and release hatched quail in Ontario without any records being kept.  The genetic composition of these captive populations is clearly different from wild stocks (often differing in appearance as well, judging from specimens in the National Museum of Canada), but no study has been undertaken to quantify these differences.  Since many of the small populations scattered through southern Ontario arise from repeated reintroduction attempts, there is a distinct possibility that the genetic composition of native populations could be compromised by interbreeding with released birds.

Hunting has never been considered to be a cause of population decline as long as adequate habitat is maintained (Brennan 1999). Although, a limited hunting season was still in effect in part of southwestern Ontario into the early 1990s, hunters realized the seriousness of the decline and not only voluntarily stopped hunting, but also began doing some habitat restoration where they could (P. Hunter, Pers. Comm., 1999). Hunting pressure was eliminated, and the hunting season has been closed now in southwestern Ontario. The population, which has appeared to be stable in the province for the past few years, has a chance to recover. Given the low population level, however, that might take some time, if not accompanied by releases of additional birds (Roseberry and Klimstra 1984).

Apparently feral cats are also a problem in the area (A. Woodliffe, Pers. Comm.), and can have serious effects on many breeding birds including bobwhite.

Severe winter weather where adequate suitable habitat was lacking has been responsible for further decimating the remaining bobwhite population. Persistent deep snow and prolonged cold are the most serious causes of winter mortality (Robel and Kemp 1997). In recent years the trend has been to milder winters with less snowfall. Weather does not seem to be a big problem in the U.S. except in the northern states within the range, where it may be a severe problem as it can be in Ontario. But, as the populations in Canada are essentially isolated from U.S. populations in this non-migratory species, we cannot expect to have any natural recruitment here from the U. S.

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