Science Notes 2017, Volume 12, Number 4

2017·1.8 MB·English

by  Missouri Department of Conservation, Resource Science Division

MDC Resource Science

Linking Wetland Management Decisions to
Secretive Marsh Bird Habitat Use During Spring
Migration

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Sora
Virginia Rail

Missouri Department of Conservation (MDC) 2017 VOLUME 12 NO. 4
Linking Wetland Management Decisions to Secretive Marsh Bird Habitat Use During
Spring Migration on Public Wetlands in Missouri
By: Evan B. Hill, University of Missouri; Elisabeth B. Webb, USGS Missouri Cooperative Fish and Wildlife Research Unit and
Doreen C. Mengel, Missouri Department of Conservation
Background Information: Several secretive marsh bird bulrush, whereas Virginia rail and American bittern
(SMB) species are listed as “Critically Imperiled” in Missouri; pioneered into wetlands with a 50:50 mix of open water to
however, little information exists on SMB distribution and emergent vegetation.
habitat use within the state. As a result, wetland managers
are uncertain as to how much SMBs use Missouri wetlands Management Implications: This project addressed
and the wetland processes they need to emulate in order to whether SMBs are using Missouri wetlands during spring
provide habitat for this guild of species. For this Science migration; clearly they are.
Note, we focus on the migratory SMBs.  Water-level manipulation to promote moist-soil vegetative
communities is likely compatible with habitat use by
Methods and Results: To address these concerns, we spring migrating sora, Virginia rail and American bittern;
designed and implemented a two year study (2013 and 2014) mean drawdown duration on wetlands with active water
that included repeated call-back surveys to detect five SMB manipulation was 45 days and generally encompassed
species (Virginia rail (Rallus limicola), sora (Porzana the five week migration window during which these
carolina), king rail (R. elegans), least bittern (Ixobrychus migrants are in Missouri.
exilis) and American bittern (Botaurus lentiginosus)) on 107  Considerable uncertainty remains as to how SMBs use
wetland units across 8 Conservation Areas and 4 National wetlands across the broader Missouri landscape
Wildlife Refuges throughout Missouri. We considered Virginia (including wetlands on private land), movements among
rail, sora, and American bittern primarily as migrants through wetland habitats, and migration stopover duration.
Missouri, whereas we considered king rail and least bittern Additional investigation to address these questions would
primarily as breeding in Missouri. further inform management decisions targeted toward
SMBs.
Wetland units were categorized as active or passive based
on water-level manipulation strategies implemented each 0 0 0
spring. Active sites were those in which managers
manipulated a water control structure with the intent to draw
000 000 000
down water levels on a given wetland, whereas water levels 2
ro
in passive sites were not manipulated. Water levels in either E
~ "0 ' "0 ' "0 '
management category could fluctuate due to rain, floods, UJ
>-
evapotranspiration, or soil infiltration. We stratified sampled u .,. .,. .,.
rCo 0 0 0
wetlands by dominant vegetation communities and placed a Cl.
:,
SMB survey point within each. More details on study uu
methods, results and discussion can be found in Hill (2015). 0 0N N0 N0
 We detected 909 sora, 254 least bittern, 181 American
bittern, 99 Virginia rail and 9 king rail, during the spring 00 00 00
migration period (early April through mid-May) indicating 50 100 150 200 0 50 100 150 50 100 150
that Missouri’s public wetlands are being used as spring Begin Day of Total Duration of Mean Water
Drawdown Initiation Drawdown in Days Depth (cm)
migration stopover locations.
 Water management only appeared to influence initial Figure 1 - Predicted American bittern (Botaurus lentiginosus)
wetland occupancy by soras and bitterns. Soras keyed in occupancy estimate as a function of the initiation date, the
on wetlands with slower drawdowns (≥100 days), drawdown duration, and the average water depth (cm) at a site.
whereas least bittern preferred wetlands with later
drawdowns (initiated in mid- to late-May). American Citation:
bittern occupancy increased with slower drawdowns Hill, E.B. 2015. Linking wetland management decisions to secretive
marsh bird habitat use during spring migration and summer
(>150 days), later drawdowns (initiated in July), and
breeding on public wetlands in Missouri. M.S. Thesis.
deeper water (≥150 cm) (Figure 1).
University of Missouri – Columbia. 117 pp+app.
 Once birds occupied a wetland, vegetation characteristics
were generally more important in predicting whether they
pioneered into other wetlands. Sora appeared to prefer
wetlands with denser vegetation and a higher percent
coverage by emergent vegetation such as cattails or
For more information, contact: Keywords: rails, sora, Virginia rail, king rail, American
Missouri Department of Conservation bittern, least bittern, spring migration, migration, ecology,
Resource Science Division wetland, water-level manipulation
2901 West Truman Blvd.
Jefferson City, MO 65109

573-751-4115 2017 VOLUME 12 NO. 4
[email protected]