Wednesday, July 4, 2012

An Excuse to Walk in the Woods

Scarlet Tanager (Piranga olivacea)
(Note: The images illustrating this post are not mine; they are borrowed from the Web.)

Last Saturday morning, (June 30) I completed my 2012 series of censuses of the birds that are breeding in the largest forest in our natural area.  This is the 21st straight year that I have been marching through the woods, starting at the crack of dawn and finishing up about 9 a.m.

This project began in 1991 when the Cornell Laboratory of Ornithology asked birders nationwide to conduct a census of the birds breeding in deep woods in order to assess the population status of forest interior breeders like Wood Thrushes, Veerys, and Scarlet Tanagers.  Cornell's protocol required participants to establish a transect through their chosen woodland, and to locate stopping points spaced 50 meters apart along the transect.  Then, the birders were asked to walk the transect at least eight times during each breeding season, stand quietly for 10 minutes at each designated stopping point, and record the birds heard singing or observed within 50 meters of each stopping point.  After completing eight walks, the birders were instructed to review their observations and to try (to the best of their abilities) to map territories of individual breeding pairs.

I dutifully reported my results to Cornell for the first nine years, but after the 2009 census Cornell terminated the project.  By this point, I had invested a lot of time in the woods and had also come to realize that information about birds breeding in our forest could be a valuable, independent measure of the ecological integrity of our woods and a bellwether of our success in actively restoring forest in old-fields adjacent to the existing forest.  After all, birds can "vote with their wings," and if the habitat is not to their liking, they'll move on.  So, I have continued the censuses, even though there's no platform on which to share the data.  (I did hear from the researchers at Hawk Mountain Sanctuary in the Pennsylvania Appalachian Mountains a few years ago; they, too, had continued their census after Cornell terminated the project, and they were seeking information from others who had continued to collect data.)
Red-eyed Vireo (Vireo olivaceous)
I haven't carefully analyzed all of the information I've gathered over the years, but I do have some impressions.  First, a few species that had been fairly common when I began the censuses have declined, including Red-eyed Vireos (not so worrisome, at least in this context, because they aren't really forest interior breeders) and Veerys (Catharus fuscescens) (much more of a concern, because they do need large blocks of woodland to breed). 
Brown-headed Cowbird (Molothrus ater)
On a far more positive note, Brown-headed Cowbirds, which are nest parasites, have all but disappeared from the woods, though initially they had been numerous.  Also on the very positive side, Wood Thrushes remain among the most common breeders in the forest; many of my suburban ornithologist colleagues would be green with envy over the number of breeding Wood Thrushes in my woodland.
Wood Thrush (Hylocichla mustelina)
Another observation:  the forest topography is gently rolling, with two rills flowing through shallow valleys draining from the east to the west.  More birds select the south-facing slopes of these valleys than the north-facing slopes--I'm guessing because the south-facing slopes are a bit warmer.  I have two other observations that will ring true with every experienced birder.  First, the birds sing less frequently as the time after dawn lengthens, so I have to alternate the direction of my walks in the woods, starting one time at the north end of the transect to catch the north-end early morning singers, and then at the south end on the next walk to catch the south-end early birds.  Second, the woods become increasingly quiet as the breeding season progresses; the birds have established their territories, breeding, brooding and raising young are underway, and there's less and less need to defend boundaries.  So, for the human observer, the last few walks in the series of eight, especially the sections containing the "late morning" stopping points observed from 8-9 a.m., can become pretty tedious affairs because there's so little "action" to document.

And, as for last Saturday's final census.  Well, I was only in the woods for one hour from 7-8 a.m. observing six stopping points (instead of the usual 18) because this was a special "ninth" walk to make-up for the six stopping points I was unable to observe on May 25 when a ferocious early morning thunderstorm drove me out of the woods to seek cover under a neighbor's shed.         

8 comments:

John Gray said...

I didnt see you note that you didnt take the photos and was just about to congratulate you on your talents!!!

Grizz………… said...

You've hit on a genuinely worthwhile reason for an early morning woods walk…though I believe any reason is good enough. I might, for example, feel compelled to do so because I passed a dozen Buicks on the road the way to the grocery the day before…though I suppose if one were a real stickler for technicalities, they would claim this was actually an excuse rather than a bona fide reason.

I say whatever works.

Anyway, your willingness to keep at the survey is to be commended. Such long-term data will always be interesting and useful. And I'm glad to hear that cowbirds are becoming less numerous rather than more. From what I know, in many big woods areas, cowbirds are going ever deeper into the interior to find host nests and parents. That you've found the trend going the other way is good news.

I'd would also like to hear anything you've noted re. the scarlet tanagers…increasing, decreasing, holding steady? I don't have them around here, but see one now and then in the hill country of the southeast. And there are a few big woods tracts west of here where they're found, too. I've always loved scarlet tanagers.

Enjoyed the post.

John "By Stargoose And Hanglands" said...

Good work, Scott. In these latitudes you have to be out of the house and in the wood by about 4 in the morning to hear the start of the dawn chorus; it would take a certain ampount of dedication to do that on a regular basis. I have just about enough dedication to do it about once a year!

Scott said...

John (Gray): I wish that I had the patience (and the equipment) to make images like the ones that accompanied this post. I could afford the equipment, but I'll never have the patience.

Scott said...

Grizz: With regard to Scarlet Tanagers (10% of which, nationwide, breed in Pennsylvania, by the way): I almost always have one pair breeding within my 40-acre transected woodland, and sometimes two pairs. This year, I had one pair. Their breeding pattern is often disconcerting, though, because frequently I hear/see them along one section of the transect for two or three walks and think I have them "nailed down" for the year, and then they'll move to another section of the transect (which is what they did this year). At least they stay in the woods, though, and don't move on to another forest. Hearing and observing them is one of the highlights of my visits to the woods, and I'd think there'd be something really amiss in the world if I didn't have a pair to observe each year.

Scott said...

John ("By Stargoose and Hanglands"): I'm "lucky" that Kali's schedule changed a few years ago and she has to get up for work routinely at 5:40 a.m. When it comes time for my conducting the censuses, getting up 40 minutes earlier at 5:00 a.m. is not as painful as it was when we regularly awoke at 6:20 a.m.

If I get up at 5:00 a.m., I'm in the woods at 5:30 or 5:40, and that seems to be adequate for the censuses. The birds start to sing about 5:00, but they're still active enough when I'm finishing up at 9:00 (or so I tell myself). The Cornell protocol specified a census period of within 3 hours of sunrise or 3 hours of sunset. Interestingly, many years ago I decided to give the "3 hours of sunset" window a try, but found that the birds were much more active in the morning, so I quickly abandoned evening surveys.

packrat said...

Excellent work you're doing, Scott. It's always heartening to know that earnest lovers of the natural world (like you) are afoot in the environment.

I often visit the Cornell website to research birds I have seen in the Chihuahuan Desert.

Scott said...

Thanks, Packrat. Sometimes, when it's getting near the end of the census season, and near the end of the day's transect, and my stomach's rumbling with hunger, and the sweat's pouring down my brow, and the deer flies are strafing my bald noggin', I wonder why I do this.