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.
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More Smoke. . .Update: October 9, 2013

I just returned from another visit to the new Project Coyote search area. I have a book coming out in February and will be unavailable during what’s typically considered peak search season. I plan to make 2-3 more trips between now and mid-January. Frank Wiley’s work responsibilities have kept him out of the field since August 1st, except for a very brief visit a few weeks ago. There have been no indications of recent woodpecker work of any kind on the target trees described in the July 6th update. I found another promising and recently scaled feeding tree in the same general area, and we have moved one of our two Reconyx cameras to that location.  The trip was a very valuable one for a number of reasons, and assuming that Ivory-billed Woodpeckers are present, we may have some new insights into their behavior.

Weather conditions were extremely difficult from October 2nd through October 5th. Although insects and ticks were nowhere near the issue they were in July, the heat was nearly as intense, and humidity was so high that pre-sunrise hikes into the habitat left binoculars and camera lenses fogged and bodies drenched in sweat. On October 4th, a sudden rainstorm at a time when forecasts predicted a 0% chance damaged or destroyed my camera and ended the field day shortly after noon. Frank Wiley joined me on the 5th, and we were caught in a similar but shorter storm that did nothing to bring down the temperature and added an additional layer of unpleasantness to our late afternoon hike out of the habitat. Conditions were more moderate on the 6th, with the humidity way down and temperatures in the 70s.

It’s also worth mentioning that this weekend was the opening of squirrel season in Louisiana, so there were there were quite a few people in the area, but mostly on the outer edges of the swamp. From Friday-Sunday, gunfire was frequently audible, especially between 7 and 10 am.

I arrived at the location on Wednesday afternoon and spent a couple of hours in one of our hot zones. I did not see or hear anything suggestive. Thursday and Friday were somewhat more interesting, as I discovered some trees that had been fairly recently scaled, including the one on which we’ve now focused a camera (Figs. 1 and 2). While the photographs show work near the base of the tree, there was similar scaling higher up on the bole. The top of this snag had blown down, but death was recent, and the the bark was tight and hard to remove with a hunting knife.

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Fig. 1. Recent scaling  with insect exit tunnels at the base of a tight bark snag

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Fig. 2. Large bark chip beneath fresh scaling

I also found a feeding tree that had both fresh and obviously old and weathered scaling (Fig. 3). This lends further support to the idea that ivorybills return to feeding trees many months apart; we observed something similar on a scaled tree in our old search area in 2010 but did not have a camera on the tree when the second round of scaling took place.

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Fig. 3. High branch scaling with signs of at least two visits. Note weathered, older scaled areas and the more recent darker patches at the base and top of the right fork

We suspect the return visits are a response to Cerambycid life cycles, and it appears that scaling takes place both in and out of breeding season. This suggests that maintaining camera traps on suspected feeding trees for extended periods may prove to be a fruitful approach, so we plan to leave our cameras in place for the foreseeable future.  We’d welcome input from entomologists about beetle egg laying, pupation, and emergence, as this might eliminate the need for leaving cameras in place for months on end and enable us to deploy them on suspected feeding trees at optimal times.

Over the course of the visit, I noticed a good deal of high branch scaling similar to that described by Tanner and consistent with the appearance of other Campephilus woodpecker feeding sign (Figs. 4-6).

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 Figs. 4-6. Examples of high branch scaling found October 3-4, 2013

 On Thursday and Friday, October 3rd and 4th, I heard isolated ambient double knocks while I was in the vicinity of the feeding tree discussed in my July 6th post. There have been numerous auditory contacts in this area in recent months. Nevertheless, I do not have a high confidence level with regard to these particular sounds, especially because they were isolated and no second observer was present.

On Saturday, October 5th, Frank and I visited the area a few miles to the north where we heard the loud single knock in July. It still remains largely unexplored, but the parts of it we’ve visited are magnificent, top quality habitat, with numerous large trees, abundant standing dead wood, and almost no signs of human activity. At approximately 11:00 am, we heard a single knock that came in apparent response to a series of ADKs. At 1:30 pm, we heard an ambient double knock. In both instances, we agreed about the quality of the sounds (including that they were unlike the gunfire we had been hearing on and off throughout the day) and the direction from which they originated.

Conditions on Sunday, October 6th were a dramatic departure from the preceding days. A front had passed through well before dawn, so the temperature and humidity were moderate. We were into good habitat in the southern search area by sunrise. At 8:28 am, we heard a series of kent-like calls to the northeast of our location. Frank heard two in close succession, the second note lower than the first; I counted six altogether but missed the descending second note. We agreed that they were consistent with other suspected Ivory-billed Woodpecker calls that we have heard and recorded in this area and those we heard and recorded in January 2010 in the old Project Coyote search area. To my ears, these calls are somewhat similar to the ‘kik’ call of the Cooper’s Hawk (with which I am very familiar) but richer and less harsh in tone.

After retrieving one of our Reconyx cameras and moving it to the new suspected feeding tree, we headed north to adjust the placement of our other camera. This is where I heard ambient double knocks to the northeast on Thursday and Friday. At approximately 1:45 pm, we both heard two double knocks to our southwest. These appeared to come in response to and within five minutes of a series of ADKs that Frank had performed. Frank heard a third double knock two to three minutes after the first two, but I missed it. Two to three minutes after Frank heard the double knock, we both heard a single knock, apparently from the same location. We waited an additional ten to fifteen minutes and heard nothing further, leaving the location at a few minutes after 2 pm and walking in a southwesterly direction.

At 2:15 pm, I heard several kent-like calls, identical in quality to the ones heard earlier in the day. I stopped and asked Frank, “Did you hear that?” He indicated that he had not, but another call followed, and it was readily audible to both of us. We agreed that the calls seemed to have come from the same general area as the double knocks we had heard approximately a half-hour before.

As we discussed what had been an extraordinary day, even for this area where the possible contact rate has been extraordinarily high, Frank noted that no kent-like calls had been heard since early March, when another searcher and I heard and recorded suggestive calls in the morning and afternoon, this despite frequent visits to the area by several searchers, including Frank’s almost daily presence from late June until August 1st. Frank has been in the field at all seasons, and I visited the former search area into June in 2010. We are not aware of having heard any suggestive calls before October 1st or after mid-April and certainly not any series of calls. We are aware of kent-like sounds being recorded during summer in other parts of Louisiana but suspect that calls are rare during the late spring and summer months and that the dramatic change in weather conditions and the first cool day of the year may have triggered the vocalizations.

To be continued. .

Edited to add: I have re-examined the high branch scaling in Figure 6., and on a closer look, there are indications that the bark has been scaled in layers. I will leave the image up, but I think it may well be Pileated Woodpecker work; it is certainly not what I would classify as Grade A. The other posted examples do not share this layered appearance. While I always look for ‘Tanneresque’ scaling, it has been my view for some time that (Tanner notwithstanding) the most suggestive and perhaps diagnostic work can be found on boles rather than on high branches.