People often ask about the hawk count year-to-date numbers compared to last year, especially this year since it seems like this year's count is substantially higher. And it is, 6354 raptors higher, or about 28%. Break out the champagne, raptors are on the upswing, right? Well, not exactly. First, here are the numbers:
Cape May Cape May Point, New Jersey, USA ------------------------------------------------------------------- LAST YEAR THIS YEAR Species 2009 thru Oct. 12 2010 thru Oct 12 ------------------ ----------------- ---------------- Black Vulture 90 89 Turkey Vulture 368 438 Osprey 2412 4259 Bald Eagle 336 315 Northern Harrier 349 979 Sharp-shinned Hawk 8145 11764 Cooper's Hawk 3963 2523 Northern Goshawk 0 0 Red-shouldered Hawk 8 25 Broad-winged Hawk 599 1104 Red-tailed Hawk 303 225 Rough-legged Hawk 0 0 Golden Eagle 0 0 American Kestrel 3341 4268 Merlin 1455 1627 Peregrine Falcon 967 1075 Unknown Accipiter 0 0 Unknown Buteo 0 0 Unknown Falcon 0 1 Unknown Eagle 0 0 Unknown Raptor 0 0 ----- ----- Total: 22338 28692Looks pretty good, right? Everything but Cooper's Hawk and Red-tailed Hawk is up. We've been joking that maybe we've got a better hawk counter than last year, but the flat out truth is that there's a LOT of noise in migration count data, and one season does not a trend make. I was talking with Dr. David Mizrahi, NJ Audubon VP of Research, about this very thing yesterday. The only reason we can make statements about population trends using migration count data is because we have many years of it, 34 to be exact, to smooth out the noise.
This year, in my opinion, one of the biggest noise makers is the fairly steady stream of cold fronts and following northwest winds. These conditions increase Cape May hawk counts - and butterfly counts, for that matter. Layer onto that variable the annually changeable timing of fronts and strong west winds; frequency of high flight days, when light winds and strong thermals allow some (or most) birds to fly so high they are literally out of sight and go uncounted; annual breeding success, which varies substantially year-to-year and yet may not amount to a trend; and yes, observer variability. Trend analysis does reveal statistically significant long term patterns, e.g. up in Bald Eagles and down in American Kestrels, but the only way we can keep track of these changes is to. . .keep track, every year!
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