Saturday, May 14, 2011

Fire return intervals and songbirds


If the general public knew how many surveys of all forms of biota were conducted annually in the Ozarks, if they knew how many hours were spent peering into a sampling quadrat or birding for hours at a time or looking for butterflies and host plants to attain knowledge of populations in a given area, they'd probably start asking for reports, for a status update, for an analysis of all that data collection. Considering that I, too, am a member of the general public, I have made it my obligation to not only collect mounds and mounds of data, but to analyze it and to write reports based on all those hours of fieldwork.

It's time consuming, entering all the veg data into a program that calculates species richness, floristic quality. It's equally time consuming to analyze wildlife data to determine the same set of results--species richness, quality of the landscape based on the conservatism of certain biota that occur there. So each winter, I enter all my data from the field season and have it analyzed. It's so time consuming that I spend most of the winter months (when I'm not setting woods on fire) at my desk, sedentary, lowering my metabolism and getting fat.

I recognize that winter ended a while ago, but just last week (sitting at my desk getting fat) I finished analyzing my bird data from a survey conducted in May-June 2010. This chunk of data was at the bottom of my stack of surveys; all of my vegetation sampling has already been analyzed (deer, fire, no fire, windstorm, recovery from exotics, cedar removal alone, cedar removal+fire, etc.). What's the point of collecting data if it's never analyzed? I guess you could do what my predecessor did: leave it for the next chump. But I'm that chump and I like to see the results of the work.

And so, I downloaded the program that calculates the presence and absence of bird populations, as well as density and probability of occurrences. It's a clunky little computer program, not at all as sleek as my floristic quality index program, but it was reliable, and respectable enough biologists are using it throughout the country. (It's really clunky. Bad programming. Required much more time that it should have.).

My birding project involved comparing two restored glades, both burned for the past 26 years at different fire return intervals. One site has burned every 2-4 years, the second site has burned less frequently, on average every 5-7 years. Both sites had serious grazing histories, as most glades in the Ozarks have. 80 years of open range grazing by domestic livestock was so totally destructive to this part of the Ozarks, I can't believe anyone in their right mind would even consider introducing domestic livestock to these same native landscapes that are already so terribly damaged from the exact same process.

Anyway. The site that burned more frequently (because it's an easy burn, surrounded by roads, and it's an easy way to hit target) lacks the distinctive shrub layer that some glades in this part of the Ozarks now have--relicts of overgrazing, of course, but still a structural component. On average, shrub height on the more frequently burned site was 2-3 m. On the site that burned less frequently, shrub height was 5-6 m. with saplings maturing out of the shrub layer. These sites share a political border, so I wanted to measure the differences in bird populations between management regimes.

The results came in late at night (it took a while to figure out how to batch load all species across all survey sites). I stood there in the office comparing both sides of the political border.

I guess I should have expected such results, but most of my bird survey work has been conducted in high quality woodlands or wetlands. This survey represented the first time I worked on awesome restored dolomite glades surrounded by really crappy, overgrazed, degraded, trashed out woods. It's easy to restore a glade in the Ozarks: cut the cedars, burn the cedars when or before they're red needle, keep the fire going for a few years to control the brush that comes with a cattle/sheep/goat grazing history (therefore, with every glade in the Ozarks). Easy. Woodland restoration requires a greater commitment.

So, which of the grassland-shrubland birds keyed into these glades for breeding and foraging? Across both sides, high densities of prairie warblers, field sparrows, indigo buntings, yellow-breasted chats, Eastern towhees. But I found greater nest success of indigo buntings and field sparrows on the glade that was burned less frequently and had thicker shrub density. Both glades were extremely rich floristically, with an average FQI of 4.8-5.2 for every quadrat. Good conservative plants like Liatris mucronata, Callirhoe digitata, Carex crawei, Echinacea paradoxa, few exotics and hardly any of the old goat barn plants (some of the crotons and arennarias, e.g.) that I find in glades that are in the early stages of restoration.

I stayed up late that night looking at the results of the surveys. I compared them, I ran them through another program, and the results were the same. What concerned me about the results was not the occupancy by grassland-shrubland birds because they're obviously keying into this glade complex, regardless of the fire return interval. Nest success was interesting. But what worries me is the high number of generalist woodland birds that were detected on the glade with the more frequent return intervals. Remember, this was the easy burn site, a glade surrounded by roads and crappy woods and restorable glades, but unrestored glades. The glade nestled in a large landscape of degraded but burned woods had higher densities of the more conservative grassland-shrubland birds than the other site.

Scale. The fire return interval is important for structural reasons, and for the recovery of the grass-forb mix that attracts the necessary invertebrates that songbirds depend on for their life histories. But little piddly 60 acre burn units surrounded by thousands of unburned acres aren't contributing to the conservation of these birds as much as the largescale landscape burns that also encompass trashed out woods do. Across the political border, they're burning crummy woods, yes, but they're burning woods that have some semblance of an understory production that these same birds depend on. Bird feeder birds can be found in bush honeysuckle woods on roadsides. Conservative native landscape birds depend on native ecosystems and all the intricate workings and structure inherent within. Small patch, tiny tract burns aren't the answer to the conservation of declining bird species.

8 comments:

Mike Whittemore said...

If only private land owners were more educated on proper wildlife practices. It'd be nice if there was a system in place similar to CRP where a land owner could get compensated for properly maintaining their land - in this case, wildlife habitat rather than erosion control.

beetlesinthebush said...

Interesting, and your results feed into my ever-growing feeling that the larger landscape plays at least as big a role in how conservation units respond to management as the management itself. Bad news for small, isolated units surrounded by altered, dumb-downed landscapes.

p.s. Our paper on the Knob Noster tiger beetle should be out soon.

Allison Vaughn said...

you're right--on large landscapes, fire works naturally, creating a mosaic of landscape types. when you work with tiny little fragments, natural processes can't function properly.
You've been to the site where I did this work, by the way. I was so disappointed by the results of my study.
Looking forward to the Knob paper. That's the site of one of the earliest restoration projects in the system.

Paul Nelson said...

I know less than the number of fingers on one hand people like you who understand the true ecological workings of fire-mediated landscapes. Thanks so much for publishing the bird study results as I am on the other side of that political sense. Its only now that the Mark Twain National Forest has expanded its landscape burns to scales in excess of 25,000 acres. It is only on this scale (and perhaps larger) that we will eventually know the truth about the viability of most species large and small, fire tolerant and intolerant, and vertebrate-invertebrate. I only hope I live that long to see a restored landscape of successive hills and valleys. Thanks for revealing this truth. Paul

James C. Trager said...

Will this be published in a form such that we can read a pdf or reprint? I'd really like to read it, if (when) so...

Allison Vaughn said...

Thanks for reading, James. I plan on writing a proper paper on this, presented the data at a conference last week in a powerpoint. It's pretty interesting stuff, actually. I'll keep you et al posted on when it's in galley. My HHT bird-veg paper is about to be published, which is good, a lot of time in the field validated.

James C. Trager said...

Good to hear about the HHT paper. That is the one talk I heard at that meeting to which I refer the most since I heard it. Looking forward to a copy, when ready.
Seems to me the results of the two studies are somewhat consistent -- do you agree?

Allison Vaughn said...

Thanks James. You're right, that the larger landscape is better for the more conservative birds--probably why they're conservative. This second one was down in White River country, where the Trelease's photo was taken this week. Out on the same glade we heard chats, prairie warblers, summer tanagers, field sparrows and white eyed vireo in the first few minutes of standing out there. Going back to HHt for this year's bird work, but to a part of the park that's in the early stages of restoration. Should be interesting to see the differences between units in the park. Thanks for continuing to read, by the way.