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.
The primary objectives of the this project were: 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.
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 .
To assess the distribution and habitat use of king rails along the Upper Mississippi Valley, we conducted repeated call-broadcast surveys at 83 sites in 2006 and 114 sites in 2007. We detected king rails at 8 sites in 2006 and 14 sites in 2007. We found king rails concentrated at Clarence Cannon National Wildlife Refuge, an adjacent private Wetland Reserve Program land, and B. K. Leach Conservation Area; these areas were located in the Mississippi River floodplain in northeast Missouri. Using the program PRESENCE, we estimated detection probability and incorporated habitat covariates into the estimation of site occupancy. We tested the fit of the data across a series of models which included percent cover of tall emergent vegetation (e.g. Typha latifolia, Sparganium americanum), short emergent vegetation (e.g. Eleocharis palustris, Leersia oryzoides), woody vegetation, and interspersion of water and vegetation (2007 only) within 50 m of the survey location.
To compare the habitat use of nesting and brood-rearing king rails, we randomly sampled 5-m plots within used and unused habitats during the nesting and brood-rearing seasons to measure water depth and determine dominant cover type. We fit logistic regression models to the data and selected among candidate models using AICc. We used the regression coefficient of top models to calculate odds ratios for habitat use.
In 2006 and 2007 we attempted to capture 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.
The top occupancy model for 2006 included woody vegetation while the top occupancy model for 2007 included short emergent vegetation, tall emergent vegetation, interspersion, and woody vegetation. Site occupancy was negatively related to woody vegetation cover in both years and was positively related to interspersion (measured in 2007 only). The relationship between site occupancy and cover by short and tall emergents was less clear.
Nesting adults were more likely to use sites dominated by short emergent vegetation and deeper water, while broods were more likely to use sites dominated by short emergent vegetation and shallower water, and avoided areas dominated by tall emergent vegetation.
We did not capture any king rails in 2006. 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 readily 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.
Our results suggest that wetlands with little or no woody vegetation cover and high interspersion of water and emergent vegetation are suitable for king rail nesting. Thus, biologists that manage wetlands for king rails should consider using techniques (e.g., burning, disking) that reduce encroachment by woody vegetation (Fredrickson and Taylor 1988). Creation of micro-topographic depressions also can enhance vegetation-water interspersion (Eddleman et al. 1988) and may improve king rail habitat. Nesting King Rails need stands of emergent vegetation with adequate flooding to provide concealment and protection from predators. King Rail broods need slightly more open habitats with emergent vegetation and shallow water to provide closely associated hiding and foraging areas. These management strategies would also benefit other secretive marsh birds (Lor and Malecki 2006).
For detailed information, consult my thesis or the following publications that resulted from this project:
Darrah, A. J. and D. G. Krementz. 2009. Distribution and habitat use of king rails in the Illinois and Upper Mississippi River Valleys. Journal of Wildlife Management 73: 1380-1386.
Darrah, A. J. and D. G. Krementz. 2010. Occupancy and habitat use of the least bittern and pied-billed grebe in the Illinois and Upper Mississippi River Valleys. Waterbirds 33: 367-375.
Darrah, A. J. and D. G. Krementz. 2011. Habitat use of nesting and brood-rearing king rails in the Illinois and Upper Mississippi River Valleys. Waterbirds 34: 160-167.
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.
Eddleman, W. R., F. L. Knopf, B. Meanley, F. A. Reid, and R. Zembal. 1988. Conservation of North American rallids. Wilson Bulletin 100:458-475.
Fredrickson, L. H., and T. S. Taylor. 1982. Management of seasonally flooded impoundments for wildlife. U.S. Fish and Wildlife Service Resource Publication 148, Washington, D.C., USA.
Haramis, M.G. and G.M. Kearns. 2000. A radio transmitter attachment technique for soras. Journal of Field Ornithology 71(1): 135-139.
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.
Lor, S., and R. A. Malecki. 2006. Breeding ecology and nesting habitat associations of five marsh bird species in western New York. Waterbirds 29: 427-436.
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.