Download Dolichonyx oryzivorus Species Code: B-BOBO Status: Blue

BOBOLINK
Scientific Name: Dolichonyx oryzivorus
Species Code: B-BOBO
Status: Blue-listed
Distribution
• Provincial Range
In the summer the Bobolink occur in the Sub-Boreal Interior, Central Interior, Southern Interior
Mountains, and Southern Interior Ecoprovinces. The Bobolink’s breeding distribution ranges from a
narrow corridor of the southeastern Cariboo-Chilcotin, south to the southern Okanagan valley and east
to the Kootenays (Vandamme 1995).
• Elevational Range: Sea-Level to 1300m.
• Provincial Context
Bobolink numbers in British Columbia are declining probably due to loss of habitat. It is estimated that
there are less than 500 birds in British Columbia (Vandamme 1995).
• Project Area:
Ecoprovince: Central Interior
Ecoregions: Chilcotin Ranges and Fraser Plateau
Ecosections: Central Chilcotin Ranges (CCR), Chilcotin Plateau (CHP) and Fraser River
Basin
(FRB)
Biogeoclimatic Zones: BGxh3, BGxw2, IDFxm; IDFdk3; IDFdk4; MSxk; MSxv; ESSFxv2,
ESSFxvp2; SBPSxc
The ecosections and biogeoclimatic zones that have been italicized indicate areas within the
project area, that have suitable habitat for the species under consideration, and have therefore
been rated.
Ecology and Key Habitat Requirements
Bobolinks occur in tall grass, flooded meadows, dense pasture or alfalfa fields. During the growing
season Bobolinks are mainly insectivorous and feed on caterpillars, grasshoppers and beetles and
occasionally on grains and seeds (Vandamme 1995). The Bobolink responds positively to moderate
grazing in tall grasslands and negatively to heavy grazing in shorter grasslands (Vandamme 1995). In
British Columbia, the Bobolink appears to be dependent on artificially cultivated habitats and therefore
much of its habitat is on privately owned land.
Habitat Use and Life Requisites
The life requisites that will be rated for Bobolink are: living and reproducing (eggs) which are
described in detail below.
• Living
Crop damaging insects are the primary diet of Bobolinks during the growing season. They feed and
seek cover in tall grass areas, flooded meadows, prairie, cultivated fields and alfalfa and clover fields
(Vandamme 1995).
• Reproducing
Eggs are laid in June to July and hatch after an incubation period of 10-13 days (Vandamme 1995).
Bobolinks breed in cultivated fields and moist meadows. Plant species that have been found common
to breeding sites are poa sp., carex sp., horsetails, buttercups, daisies, red and white clover, thistle,
dandelions, purple vetch and alfalfa (Vandamme 1995). Suitable breeding habitat can be found in the
Bunchgrass, Ponderosa Pine, Interior Douglas-fir and Interior Cedar-Hemlock biogeoclimatic zones
(Vandamme 1995).
Seasons of Use
Bobolink are a migratory species and are only in the study area for the growing season. The Living life
requisite is required for the growing season and the Reproducing life requisite is only required for the
breeding season. Table 1 summarizes the life requisites required for each month of the year.
Table 1. Monthly Life Requisites for Bobolink.
Life Requisite
NA
NA
NA
NA
Living, Reproducing (eggs)
Living, Reproducing (eggs)
Living, Reproducing (eggs)
Living
NA
NA
NA
NA
Month
January
February
March
April
May
June
July
August
September
October
November
December
Season
Winter
Winter
Winter
Winter
Growing
Growing
Growing
Growing
Winter
Winter
Winter
Winter
Habitat Use and Ecosystem Attributes
Table 2 outlines how each life requisite relates to specific ecosystem attributes (e.g., site
series/ecosystem unit, plant species, canopy closure, age structure, slope, aspect, terrain
characteristics).
Table 2. Terrestrial Ecosystem Mapping (TEM) Relationships for each Life Requisite for Bobolink
Life Requisite
Living Habitat
Reproducing Habitat
(eggs)
TEM Attribute
- site: site disturbance, structural stage
- soil/terrain: flooding regime
- vegetation: % cover by layer, plant species
- site: site disturbance, structural stage
- soil/terrain: flooding regime
- vegetation: % cover by layer, plant species
Ratings
There is an intermediate level of knowledge on the habitat requirements of Bobolink in British
Columbia and thus, a 4-class rating scheme will be used.
• Provincial Benchmark
Ecosection:
NOB
Biogeoclimatic Zone:
IDFdm, IDFdk or IDFxm
Habitats:
grasslands/cultivated fields
• Ratings Assumptions
1. Cultivated hayfields and weedy pastures will be rated up to moderate for living and reproducing.
2. Moist grassland habitats will be rated up to low for living and reproducing.
Table 3. Summary of habitat requirements for Bobolink in the study area.
Season
Growing
Life Requisite
Living (LI)
Structural Stage
2
Growing
Reproducing (RE)
2
Requirements
Tall grass, flooded meadows, dense pasture or alfalfa
fields.
Tall grass, flooded meadows, dense pasture or alfalfa
fields.
• Ratings Adjustment Considerations
Final capability and suitability map products may incorporate 1) landscape heterogeneity and
connectivity; 2) habitats adjacent to significant anthropogenic disturbance regimes (e.g. settlements);
3) interspersion of different structural stages within the landscape.
Please note that eventhough structural stage substage or modifiers and stand composition modifiers
were employed in the original mapping, these units (other than structural stage modifier 3a and 3b)
have not been included in the final ratings tables. This is because the ratings for the modified and
unmodified ecosystem units are the same and including these units in the final ratings table would in
turn make the ratings table too cumbersome. In instances where the modified ecosystem unit (either
structural stage substage or modifiers and stand composition modifiers) is mapped, please use the
wildlife habitat rating for the same unmodified ecosystem unit.
References
Vandamme, L.M. 1995. Status report on the Bobolink (Dolichonyx oryzivorus) in British Columbia.
B.C.
Environment, Wildlife Branch, Nelson, B.C. 16pp.
Stevens, V. 1993. Wildlife Diversity in British Columbia: Distribution and Habitat Use in
Biogeoclimatic Zones Draft Report. Wildlife Interpretations Subgroup. B.C. Ministry of
Environment, Lands,
and Parks. B.C. Ministry of Forests. Victoria B.C.