This was the seventh year of systematic goshawk nest monitoring on Haida Gwaii. Monitoring including several visits to each known nest area, and if no birds were initially located, then goshawk playback surveys were conducted throughout the area, and in adjacent areas of suitable habitat, to establish if the birds were present and possibly using a new nest. A total of 13 known nest areas were monitored, and in addition one new nest area was located in the Crease Creek Watershed. Of the known nests, birds were present at 58% of the nests in early spring during a time when nesting is initiated, and later 38% of the known sites successfully fledged young. This is the highest rate of breeding success seen since systematic monitoring was initiated, and it is comparable to the rate of success seen in other goshawk studies. This increase in success was possibly in response to an increase in prey, with observed increase in squirrels and potentially other prey, probably in response to a peak in cone production seen in the Fall of 2005. The one new nest at Crease Creek fell within our observed spacing pattern of nest areas on the islands, but this year also saw birds breeding at the Survey and Three Mile sites, which are closer together (6 km apart versus the previously observed 9 km) than encountered prior to this year. This indicates that in some cases adjacent nest areas may be closer together than previously known. At another site where the nest areas are only 3 km apart, (Ain and Upper Hancock) no evidence of breeding was seen at either site, so we still have no evidence to determine if these nests are used by the same, or adjacent pairs. Looking more closely at those territories in which breeding was successful, we see that at the 5 km radius home range scale, the territories with the smallest area (post harvest and/or natural), of medium to high suitability goshawk foraging habitat, failed to fledge young, while those with the greatest amount of suitable habitat were typically successful in fledging young. The increase in breeding success in 2006, coupled with the high number of territories (60-80%) in which birds were detected, during early season nest checks in 2007, was very encouraging. It suggests that enough birds are still present to ensure the population will persist on the islands, if a long-term landscape management strategy for suitable goshawk habitat, at the spatial scale of individual goshawk home ranges, is implemented. However, the results from this year do support the earlier work indicating that there is a potential foraging habitat threshold, and that we need to ensure we manage for the required area and suitability of foraging habitat, if we are to remove the threat to the long-term viability of the population.
prepared by Frank Doyle.
Doyle, Frank I.. 2007. Breeding success of the goshawk (A.g. Laingi) on Haida Gwaii/Queen Charlotte Islands 2006: is the population continuing to decline?. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2007MR087