Advertisements

Encounter Rate

      A poster on the Ivory-billed Woodpeckerl Researchers Forum raised a couple of questions about sightings and their quality, and about our encounter rate. I thought I’d take this opportunity to respond here.
      A number of people have had possible sightings in this area. Quality is a subjective term, but it’s safe to say the quality has varied. In most cases, the sightings have been by single observers. A few have involved perched birds. Distinctive features – black crests, malar and dorsal stripes and bills – have been noted in several instances; however, most have been fleeting glimpses of birds in flight. One recent flyover may have involved a pair – field marks were seen on one of the two birds. Just as we see little point in posting additional audio unless conclusive documentation is obtained, we don’t think that posting details of sightings serves much purpose, unless it’s a robust, two-person observation or is accompanied by a clear photograph.
      A little background on the encounter rate. I made my first search trip to Arkansas back in April 2007. Since then I have spent countless days in the field, probably upwards of 100 by now, in Arkansas, South Carolina, Florida, and Louisiana. I’ve learned a lot over the years; I’ve made some mistakes; I’ve written off some possible encounters as wishful thinking and have tried to maintain a healthy self-skepticism. I’ve also been somewhat obsessed with finding a category of feeding sign that is beyond the physical capacity of a Pileated Woodpecker to produce and is therefore diagnostic. As discussed in some of the recent posts, I believe I have succeeded in this, but of course my belief remains just that and is entirely unproven.
      While we don’t count finding suggestive foraging sign in estimating the ‘encounter rate’, which is actually a possible or putative encounter rate, the quantity of scaling that I consider to be Grade A or that is congruent with Tanner’s description far surpasses what I have seen anywhere else. Our old search area was considerably more compact, and in 2009 and 2010, before the adjacent parcel was logged, it was fairly easy to find suggestive feeding sign within that compact area. Since that time, I’ve refined my criteria for Grade A scaling and have made them somewhat more stringent. Nevertheless, this year in the new search area, I have found sign that meets my criteria or fits the Tanner model on virtually every field day. During trips last year, fresh scaling seemed to have been concentrated in one or two locations, and this year it seems to be more scattered. This is purely impressionistic, but whatever the case, there is an abundance of feeding sign that is unmatched by anything I’ve seen elsewhere. And I have never seen scaling that resembles what’s shown in my May, July, and October posts anywhere else, save in the former Project Coyote search area.
      Regarding the encounter rate itself: we include all putative encounters – DKs, whether ambient or in response to ADKs, putative kents, and possible sightings – even weak possibles. We estimate that we have been having one putative encounter for every 20-24 person hours in the field. The rate was considerably higher on my recent trip but probably nowhere near high enough to change the estimate. I should also add that, purely impressionistically, this is the only location where I have heard frequent apparent responses to ADKs. We had a possible attraction in the old search area and did get apparent response DKs from time to time, but nowhere near as often as in the new search area.
      The challenge lies in figuring out where the birds are roosting and nesting, if indeed they are present. We suspect there may be a nesting pair, as auditory encounters in the southern sector have frequently involved two sources of sound. To date, we have no indication that more than one bird is present in the northern sector. We have had very little success finding cavities in either sector, but it has also been difficult to find Pileated Woodpecker roosts in the deeper parts of the swamp, even in obvious, defended home ranges.
      I will be making brief trips in November and December and probably a somewhat longer one in January.
Advertisements