photo by Noppadol Paothong, Missouri Department of Conservation
photo by Noppadol Paothong, Missouri Department of Conservation
The king rail, the largest rail in North America, is found throughout the eastern United States, reaching into southern Canada, with an isolated population in central Mexico. Along the Gulf coastal plain, populations are resident year-round, while the midwestern populations are migratory. The resident population appears to be stable and are considered a game species, while the migratory population has experienced dramatic declines over the past 30 years and are listed as Endangered or Species of Concern in many states. It is possible that the endangered migratory king rails are exposed to harvest on their southern wintering grounds.
The king rail presents a challenging research subject due to its secretive nature and low abundance. Little is known about habitat requirements throughout its range, migration routes or timing, movement patterns during the breeding season, or juvenile survival and recruitment. Such information is necessary to adequately manage habitat for king rails and to encourage population increases throughout their range.
This project is the first in a series of projects intended to build upon one another to address these issues. The primary objectives of the current project are: 1) to assess the distribution and habitat use of king rails in the Mississippi River valley in NE Missouri and along the Illinois River in Illinois; 2) to assess habitat requirements for nesting and brood rearing; 3) to assess different trapping methods in preparation for future migration studies.
From May through August of 2006 and 2007, we worked on public and private wetlands along the Mississippi and Illinois Rivers, from St. Louis to Hannibal in Missouri and to Beardstown in Illinois. The habitats in these areas included marshes, bottomland hardwood swamps, shrub-scrub wetlands, and wet meadows. The majority of sampled sites were marshes, with perennial vegetation such as cattail (Typha spp.), spikerush (Eleocharis spp.), swamp smartweed (Persicaria amphibium), and arrowhead (Sagittaria spp.).
Several steps must be taken to account for the secretive nature of the king rail. We used call-broadcast surveys to try to ellicit vocalizations, following Courtney Conway's Standardized North American Marsh Bird Monitoring Protocols . Rather than estimating abundance, we are analyzing our data as presence/absence in the program PRESENCE. This program independently estimates detection and occupancy probabilities, so that we can obtain a probability of king rail occupancy that takes into account their low detectability. To learn more about this program, visit the USGS Patuxent Wildlife Research Center .
In areas where we detected king rails, we searched for nests by walking transects in a grid pattern throughout the wetland. We also observed king rail broods, noting general behavior patterns and measuring habitat characteristics such as cover, water depth, vegetation density, and dominant plant species at brood locations.
In 2007 we captured adult and juvenile king rails using a variety of methods, including walk-in traps with call-playback lures, mist nets, and spotlights and dip nets both on foot and on ATV. We banded all captured rails and attached radio transmitters using a 3-loop thigh harness. We tracked marked rails 1-3 times daily, approaching the rail 3-4 times per week to take habitat measurements.
In 2006 we detected king rails on two refuges, Clarence Cannon National Wildlife Refuge and BK Leach Conservation Area . In 2007, we detected king rails again on these refuges, as well as 5+ rails on a private land, a single detection at Ted Shanks Conservation Area , and a pair of king rails at Spunky Bottoms , which was a new survey area for 2007. Our analyses of survey point habitat data in the program PRESENCE have shown that woody vegetation and non-robust emergent vegetation are the most important covariates predicting king rail occupancy. Woody vegetation was a strong deterrent, whereas most sites occupied by king rails were dominated by non-robust emergents, particularly spikerush and rice cutgrass (Leersia oryzoides). Contrary to expectations, robust emergent vegetation did not have a strong effect. This must be viewed with caution; robust emergent vegetation may be important for king rails at other times of the year, particularly when they first arrive at their breeding grounds, before other emergent vegetation has grown to sufficient height.
In 2006 we found 3 inactive nests and 6 broods, and in 2007 we found no nests and 5 broods. We were able to observe some broods daily for a month in both years. Small sample sizes prevent direct comparison of nest sites with brood-rearing sites. Brood-rearing areas were characterized by shallow water (up to the chicks' ankles) and patches of emergent vegetation, such as cattail, spikerush, soft rush (Juncus effusus), and swamp smartweed.
photo by Noppadol Poathong
In 2007 we captured and banded 3 adult rails and 2 juveniles, at Clarence Cannon NWR, BK Leach CA, and a private land. We did not capture any rails in our traps using call-playbacks; rails would ready approach and call in response to the player, but would not enter the traps. We captured one juvenile in a small ramp trap by placing the trap near a known foraging location, circling around, and walking toward the trap to drive the rail into it. We captured the other juvenile by flushing it into a mist net. We captured one adult at night with a spotlight, dip net, and recorded calls. The rail approached and called in response to the playback, allowing us to locate and capture the rail with the net more easily. We captured the second adult in a mist net, by luring it in with recorded calls, flusing in into the mist net and securing it with a dip net. We caught the third adult at night using a dip net from an ATV. We reserved this last technique for mid-August, when the rails were not likely to be nesting.
The first adult and the two juveniles lost their transmitters within 2 days of capture. We were able to track the second adult from 6 June until 11 July, when we found the transmitter without the harness on the ground. The rail was initially in the presence of a second adult and 2 chicks, which were less than a week old. The banded rail made 2 major movements during our tracking period; a week after its capture, it moved to another wetland unit 500 m south of its original location. After another week, it moved to another unit, this one 600 m west of its first location. We soon began seeing 2 chicks following the marked rail, which would feed them. We were unable to determine if these 2 chicks were the same 2 chicks that were present when we captured the adult, or if they were from a second brood that had been seen in the area previously.
We banded the last rail at BK Leach CA on 15 August, after capturing it at night from an ATV. Refuge manager Brian Loges tracked the rail several times per week for us, mainly to determine how long the rail remained on its breeding grounds. He last located it on 28 September, after which 2 cold fronts moved through and he was unable to locate the rail on any part of the refuge.
King rails were relatively rare in our study area, resulting in small sample sizes that make strong statistical inference about habitat use difficult. We are currently finishing up survey analyses in PRESENCE, and working on using resource selection functions to analyze point locations from adult and brood observations and radio tracking data. However, we will also rely on management history information to make general statements about the habitat requirements of king rails. Future projects will continue to build upon the current data set, and explore other little-known aspects of king rail biology including juvenile survival, migration timing, and location of wintering grounds of migratory king rails.
Conway, C. J. 2005. Standardized North American Marsh Bird Monitoring Protocols. Wildlife Research Report #2005-04. U.S. Geological Survey, Arizona Cooperative Fish and Wildlife Research Unit, Tuscon, AZ.
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Kearns, G.D., N.B. Kwartin, D.F. Brinker, and G.M. Haramis. 1998. Digital playback and improved trap design enhances capture of migrant soras and Virginia rails. Journal of Field Ornithology 69(3): 466-473.
MacKenzie, D. I., L. D. Nichols, G. B. Lachman, S. Droege, J. A. Royle, and C. A. Langtimm. 2002. Estimating site occupancy rates when detection probabilities are less than one. Ecology 83(8): 2248-2255.
Meanley, B. 1992. King rail. In The Birds of North America, No. 3 (A. Poole, P. Stettenheim, and F. Gill, Eds.). Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists' Union.