Sunday, June 2, 2013
Highlights from the North, and Thoughts About Detection Probability
When you fall asleep to Whip-poor-wills, Barred Owls, and a frog symphony, and wake to Cerulean Warblers, Pileated Woodpeckers, Chestnut-sided Warblers, Yellow Warblers, and a persistently gobbling Wild Turkey, you know you're living right. That's what it was like camping at the Sawmill Lake Campground in High Point State Park, NJ this weekend - the vocalists even drowned out the human neighbors in the campground.
Camping means you're living among the birds, and your detection probability for any birds around your campsite is understandably quite high. What I mean by detection probability is, what are the odds of you actually locating a bird by sound or sight that is there for the locating?
If a given bird is within sight or earshot of a place you are spending a lot of time (like a campsite, with dinner in the evening, morning coffee, afternoon snooze. . .), your chances of detecting it are much higher than if you pay a short visit. Thus, I feel confident that while we may have missed the Ruffed Grouse and Black-throated Blue Warblers at Kuser Bog during our hikes there, we didn't miss anything near our campsite, because we probably spent 10 daylight hours and two whole nights there over the course of the weekend.
Except, riddle me this, Batman - how come it took until the third day at the campsite before we recorded the White-breasted Nuthatch and Warbling Vireo there? Where were those birds? Maybe the vireo was a "floater" male, that truly wasn't around until day three, but the permanent resident nuthatch? He or she was just living a quiet life, or maybe feeding young and keeping a low profile.
Some birds are more vocal, or active, and hence more detectable than others. Persistent singers like Red-eyed Vireos and even Cerulean Warblers come to mind. Then there are the grouse or Winter Wrens of the world - in my experience, these guys wait silently in the shadows, when in all fairness they ought to open up a little more.
This kind of stuff always gives me angst when I compete in the World Series of Birding - yes, I've scouted the bird, yes I know it is there, but will it make its presence known during that oh-so-brief interval when my team is nearby? This is why I like camping, slow hikes, and slow mountain bike rides much better than fast-paced competitive birding.
Even at that slow pace during the weekend, we missed the grouse, the only species on the sort of year "hit list" I had for this trip that we failed to detect. The other hit-list birds were pretty much gimmee's in High Point: Common Raven, Least Flycatcher, Alder Flycatcher, Yellow-throated Vireo, Black-capped Chickadee, Cerulean Warbler. Nashville Warbler, which we found, is no longer a bird easy to find breeding in NJ, if they ever were, so I was pleased to hear one.
Ruffed Grouse is a bird with a rather low detection probability in late May to begin with, since by now they are pretty much done drumming for the year, which means you might get a drum every half hour - if you're lucky. Although friends of mine reported grouse at Kuser Bog just the day before we were there. Aaargh. My next move on grouse is to hike the heck out of their habitat over the summer, which gives me a chance of either flushing one or encountering a hen with a brood, which has happened to me more often than that particular probability should allow. More trips to north Jersey!
Posted by Don Freiday at 9:39 PM