An Eruption of Ravens - NYTimes.com We manage to count half a dozen moose survey plots before the wind comes up. It is going to be another short day. We just hope to find the Chippewa Harbor Pack before heading home. The telemetry signal of the collared wolf brings us north of Tobin Harbor, where ancient basalt juts up from the earth's crust to form the Greenstone Ridge. We circle and circle - large, fast, high circles. That's all Don can manage as wind pours over the lee side of the ridge into a turbulent chaos that cannot be seen, but can certainly be felt in the cockpit of Flagship. We never do see a wolf. But the snow is trampled down over too large an area. The pack has been here for several days. And then there are the ravens. Ravens often show us the precise location of kill sites hidden by the forest. Wolves tend to grab pieces of meat or a bone from the carcass and carry it several meters away, where they can eat without being bothered by a dominant sibling or parent. When each wolf is either asleep or feeding off-site this way, the carcass is unattended. That's when the ravens make their move: 5, 10, sometimes 15 ravens, all squawking and pulling meat from the carcass. When a wolf comes back for another piece of meat - or maybe just gets tired of the commotion - black wings flap in every direction up into the trees and above the forest canopy. Often that's what we see first - an eruption of ravens from the carcass. There are too many ravens for nothing to be going on here. But they don't seem to be focusing on any one location. There is almost certainly a dead moose down there somewhere - probably killed several days ago. Now, scattered bones are probably all that remains. So the ravens have changed their foraging strategy. Now they are picking apart wolf scats for the partly digested meat - thick and dark like tar - wrapped in undigested moose hair. These are scattered across an acre or so of land surrounding the kill site. We mark, on a map and with GPS technology, two patches of thick conifer that seem like promising locations. Maybe in smoother air we'll see more. And, if necessary, we'll hike in to see for sure whether the wolves killed a moose here. Still, we feel fortunate to have seen what we did. Today is likely to be the last day the Chippewa Harbor Pack will be at this site. Without the evidence of their presence, we probablyy would have overlooked this place and the story it has to tell. Estimating kill rate - how frequently wolves kill moose - is one of our main purposes in the Winter Study. Kill rate indicates how much food the wolves get, and it is a critical component of understanding how moose are affected by predation. We've estimated kill rate each year for the past four decades. Those numbers are the basis for much that we know about Isle Royale wolves and moose. Missing a kill site, as we almost did today, leads to underestimating the kill rate. It kills us to miss a kill site. Wednesday, Feb. 15 We spot five of the six wolves in the Chippewa Harbor Pack today. By day's end they are at Starvation Point, traveling southwest, continuing their never-ending search for another vulnerable moose. Near the end of the day we find a lone wolf feeding on bones at an old kill site. We also see tracks of wolves on Lake Desor and Lake Harvey. With daylight fading, we'll have to wait for another day to figure out who made these tracks. Today, we finish the very last moose survey plot. Hundreds of methodically flown circles, hour upon hour of intense staring, worrying about fickle snow conditions and flying conditions we depend on for counting moose. Now, we have 91 totals - the number of moose seen on each of the 91 plots. Mostly it's a collection of ones, twos and threes, some zeros, and a few fours, fives and sixes. We'll arrange these numbers according to a stratified sampling design, fit a negative binomial distribution to those numbers, maximize some likelihood functions and compare some Akaike's Information Criterion values. Sometimes science is a simple observation, but more often it is simple observations interpreted through a lens of sophisticated statistical theory. Within a day or two, we'll have an estimate for the number of moose in this year's population.