Earlier this month, I traveled to Duluth, Minnesota to bird with Naturally Avian‘s Erik Bruhnke. The timing of my trip was key, and I wanted to visit the well-known hawk watching site, Hawk Ridge, at an ideal time to see Northern Goshawk. The hawk count at Hawk Ridge is run by Hawk Ridge Bird Observatory, and Erik is employed by HRBO as a count interpreter, so it was a perfect opportunity to spend some time at the ridge. Hawk Ridge is known for getting very high numbers of raptors (including Broad-winged Hawks and Sharp-shinned Hawks by the thousands), but the site is most well-known for its high numbers of migrant Northern Goshawks.
Northern Goshawk are our largest accipiter (picture a sharpie on steroids…yea, it’s scary). They are a very wide-ranging species, and they eat anything from small mammals to large birds. In the northern parts of their range, the bulk of their diet consists of Snowshoe Hare and Ruffed Grouse, both of which share its boreal forest habitat. For this reason, Northern Goshawk numbers are very cyclic, being closely tied to the availability of Snowshoe Hare. “Irruption” years can happen following periods of a Snowshoe Hare crash, as birds are forced south in search of prey. However, there has not been an irruption of Northern Goshawk for quite some time, and at Hawk Ridge and other sites, a downward trend is noticeable. Like many raptors, Northern Goshawk are very sensitive to human disturbance, and in particular, prefer large trees of old growth forests for nesting. As with decline of most species, it is likely a combination of factors that contribute to the decline. In this case, it may be a consequence of habitat loss and fragmentation (possibly due to logging and disturbance), in combination with prey availability (which may also be adversely affected by logging).
According to eBird, Northern Goshawk numbers in Minnesota peak during the week of October 22. My trip was during the week of October 8 through the fifteenth, so I arrived just before peak Northern Goshawk migration.
I was able to spend two full days at Hawk Ridge, on October 11 and 14. On October 11, Sharp-shinned Hawks dominated the flight, with a total of over 300 individuals for the day. Temperatures were unseasonably warm, in the 50′s and 60′s, and southeast winds were not really ideal for migration. However, among the stream of tiny sharpies, a handful of giant Northern Goshawk were hard to miss. The counters tallied 5 Northern Goshawk migrating by, and the few individuals I observed in migration were all juveniles. On October 14, conditions still weren’t great for migration, with more southerly winds, and cooler temperatures and overcast skies that just weren’t conducive to producing any uplifting thermals. Sharp-shinned Hawks still dominated the flight, but Red-tailed Hawk numbers were up and nearly equal to the sharpie flight. Only four Northern Goshawk were counted on this day, and unfortunately, I missed two during an ill-timed bathroom break.
I didn’t get any winning photos of migrant goshawks, besides the above photo of a bird being released. Also, I didn’t see any adults, but the banding station had a few juvenile birds on hand for an up-close look. Northern Goshawk do look big and chunky in flight, and not surprisingly their massive size is impressive in the hand (especially after observing a Sharp-shinned Hawk in the hand). Compare the size of the bird in the first photo below (Sharp-shinned Hawk) to the size of the bird in the second photo below (Northern Goshawk), in relation to the hand of the person holding each bird.
Northern Goshawks have a bulk to them that make them look like they could swallow a small Shap-shinned Hawk in one chomp. For general comparison, the wingspan of a Northern Goshawk is closest in size, on average, to that of both the Northern Harrier and Red-shouldered Hawk, and falls short of a Red-tailed Hawks wingspan by about 8 inches. However it is their bulky wingy shape and stocky body that gives them such an intimidating look. I still hope to photograph more Northern Goshawk in flight, so I will just have to make another trip to Hawk Ridge next fall, and I will hope to get lucky this season in PA. In the week following, the high count for Northern Goshawk was 12 (on October 18) and 100 individuals were tallied for the month of October.