A Radar and Visual Study of Nocturnal Bird and Bat Migration at the Proposed Bear Review Windpark, California, Spring 2007

Report

Title: A Radar and Visual Study of Nocturnal Bird and Bat Migration at the Proposed Bear Review Windpark, California, Spring 2007

Author:

Sanzenbacher, P.; Mabee, T.; Cooper, B.

Publication Date:

October 1, 2007

Pages:

Place Published:

Houston, Texas, USA

Affiliation

ABR Inc

Sponsoring Organization:

Shell Energy

Technology:

Wind Energy, Land-Based Wind

Stressor:

Collision

Receptor:

Bats, Birds

Language:

English

Document Access

Attachment:

Access File

Citation

APA
BibTex
RIS

Sanzenbacher, P.; Mabee, T.; Cooper, B. (2007). A Radar and Visual Study of Nocturnal Bird and Bat Migration at the Proposed Bear Review Windpark, California, Spring 2007. Report by ABR Inc. Report for Shell Energy.

@techreport{Sanzenbacher-2007-,
author = {Sanzenbacher, P and Mabee, T and Cooper, B},
title = {A Radar and Visual Study of Nocturnal Bird and Bat Migration at the Proposed Bear Review Windpark, California, Spring 2007},
institution = {ABR Inc},
year = {2007},
month = {oct},
address = {Houston, Texas, USA},
keywords = {Wind Energy, Land-Based Wind, Collision, Bats, Birds},
}

Export Citation to BibTex

TY - RPRT
TI - A Radar and Visual Study of Nocturnal Bird and Bat Migration at the Proposed Bear Review Windpark, California, Spring 2007
AU - Sanzenbacher, P
AU - Mabee, T
AU - Cooper, B
AB - This report presents the results of radar and visual studies of spring nocturnal bird and bat migration conducted from 16 April–30 May 2007 (primary sampling period) and 21–30 March 2007 (secondary sampling period) at the proposed Bear River Windpark, located in Humboldt County, California. Each night we conducted radar sampling (55 nights, ~8 h/night) and visual sampling (55 nights, ~6 h/night) at two stations (Hilltop and Mazeppa Ranch) within the proposed development area.The primary goal of this study was to collect information on the nocturnal migration characteristics of birds and bats during spring migration. Specifically, the objectives of this study were to: (1) collect baseline information on migration characteristics (i.e., flight direction, migration passage rates, flight altitudes) of nocturnally migrating birds and bats; (2) visually estimate the relative proportions of birds and bats within the potential rotor-swept area of the proposed wind turbines; and (3) calculate an index of the number of birds and bats passing within the rotor-swept area of the proposed wind turbines during the migratory season. We also evaluated the influence of weather, sampling location, and date on migration passage rates and flight altitudes.The mean nocturnal flight direction of radar targets during the primary sampling period was 207° at Hilltop and 241° at Mazeppa Ranch. During the secondary sampling period the mean nocturnal flight direction was 296° at Hilltop and 273° at Mazeppa Ranch. Most targets recorded were not traveling in a seasonally appropriate direction (i.e. northerly).The mean nocturnal passage rate during the primary sampling period was 178 ± 24 targets/km/h and 172 ± 25 targets/km/h at Hilltop and Mazeppa Ranch respectively. During the secondary sampling period the mean passage rates were 73 ± 20 targets/km/h at Hilltop and 88 ± 33 targets/km/h at Mazeppa Ranch. Passage rates among all nights ranged rom 4–674 targets/km/h at Hilltop and 3–679 targets/km/h at Mazeppa Ranch.Altitude-specific passage rates (i.e., passage rates below 125 m agl) during the primary sampling period were 32 ± 5 targets/km/h at Hilltop and 31 ± 6 targets/km/h at Mazeppa Ranch. During the secondary sampling period <125 m agl passage rates were 22 ± 11 targets/km/h at Hilltop and 33 ± 15 targets/km/h at Mazeppa Ranch. Across all study dates <125 m agl passage rates ranged from 0–114 targets/km/h at Hilltop and 0–147 targets/km/h at Mazeppa Ranch.The mean nocturnal flight altitude during the primary sampling period was 368 ± 28 m agl at Hilltop and 390 ± 27 m agl at Mazeppa Ranch. During the secondary sampling period mean flight altitudes were 354 ± 39 m agl at Hilltop and 303 ± 41 m agl at Mazeppa Ranch. Mean flight altitudes among all nights ranged from 104–1075 m agl at Hilltop and 125–1046 m agl at Mazeppa Ranch.The percentage of targets recorded below 125 m agl was 17% at Hilltop and 14% at the Mazeppa Ranch station during the primary sampling period and 17% at Hilltop and 27%at Mazeppa Ranch station during the secondary sampling period.Migration passage rates increased with tailwinds and as the spring sampling period progressed and decreased as windspeeds with a tailwind increased and when ceiling heights were low. Flight altitudes increased later in the spring season.Using visual sampling methods (night vision and infrared spotlights) to identify taxa of low-altitude nocturnal migrants and other potential radar targets, we calculated the proportion of individual birds and bats in the lower airspace (<150 m agl) was 78% birds and 22% bats at Hilltop and 70% birds and 30% bats at Mazeppa Ranch during the primary sampling period and 100% birds and 0% bats at Hilltop and 75% birds and 25% bats at Mazeppa Ranch during the secondary sampling period.Assuming an average of 10 nocturnal h/d, we calculated a turbine passage rate index (number of birds and bats passing within the area occupied by each turbine each night) of 1.9–15.5 nocturnal migrants/turbine/day at Hilltop and 1.8–15.3 at Mazeppa Ranch during the primary sampling period and 1.3–10.7 nocturnal migrants/turbine/day at Hilltop and 2.0–16.5 at Mazeppa Ranch during the secondary sampling period.
CY - Houston, Texas, USA
DA - 2007/10//
PY - 2007
SP - 60
PB - ABR Inc
LA - English
KW - Wind Energy
KW - Land-Based Wind
KW - Collision
KW - Bats
KW - Birds
ER -

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Abstract

This report presents the results of radar and visual studies of spring nocturnal bird and bat migration conducted from 16 April–30 May 2007 (primary sampling period) and 21–30 March 2007 (secondary sampling period) at the proposed Bear River Windpark, located in Humboldt County, California. Each night we conducted radar sampling (55 nights, ~8 h/night) and visual sampling (55 nights, ~6 h/night) at two stations (Hilltop and Mazeppa Ranch) within the proposed development area.
The primary goal of this study was to collect information on the nocturnal migration characteristics of birds and bats during spring migration. Specifically, the objectives of this study were to: (1) collect baseline information on migration characteristics (i.e., flight direction, migration passage rates, flight altitudes) of nocturnally migrating birds and bats; (2) visually estimate the relative proportions of birds and bats within the potential rotor-swept area of the proposed wind turbines; and (3) calculate an index of the number of birds and bats passing within the rotor-swept area of the proposed wind turbines during the migratory season. We also evaluated the influence of weather, sampling location, and date on migration passage rates and flight altitudes.
The mean nocturnal flight direction of radar targets during the primary sampling period was 207° at Hilltop and 241° at Mazeppa Ranch. During the secondary sampling period the mean nocturnal flight direction was 296° at Hilltop and 273° at Mazeppa Ranch. Most targets recorded were not traveling in a seasonally appropriate direction (i.e. northerly).
The mean nocturnal passage rate during the primary sampling period was 178 ± 24 targets/km/h and 172 ± 25 targets/km/h at Hilltop and Mazeppa Ranch respectively. During the secondary sampling period the mean passage rates were 73 ± 20 targets/km/h at Hilltop and 88 ± 33 targets/km/h at Mazeppa Ranch. Passage rates among all nights ranged rom 4–674 targets/km/h at Hilltop and 3–679 targets/km/h at Mazeppa Ranch.
Altitude-specific passage rates (i.e., passage rates below 125 m agl) during the primary sampling period were 32 ± 5 targets/km/h at Hilltop and 31 ± 6 targets/km/h at Mazeppa Ranch. During the secondary sampling period <125 m agl passage rates were 22 ± 11 targets/km/h at Hilltop and 33 ± 15 targets/km/h at Mazeppa Ranch. Across all study dates <125 m agl passage rates ranged from 0–114 targets/km/h at Hilltop and 0–147 targets/km/h at Mazeppa Ranch.
The mean nocturnal flight altitude during the primary sampling period was 368 ± 28 m agl at Hilltop and 390 ± 27 m agl at Mazeppa Ranch. During the secondary sampling period mean flight altitudes were 354 ± 39 m agl at Hilltop and 303 ± 41 m agl at Mazeppa Ranch. Mean flight altitudes among all nights ranged from 104–1075 m agl at Hilltop and 125–1046 m agl at Mazeppa Ranch.
The percentage of targets recorded below 125 m agl was 17% at Hilltop and 14% at the Mazeppa Ranch station during the primary sampling period and 17% at Hilltop and 27%at Mazeppa Ranch station during the secondary sampling period.
Migration passage rates increased with tailwinds and as the spring sampling period progressed and decreased as windspeeds with a tailwind increased and when ceiling heights were low. Flight altitudes increased later in the spring season.
Using visual sampling methods (night vision and infrared spotlights) to identify taxa of low-altitude nocturnal migrants and other potential radar targets, we calculated the proportion of individual birds and bats in the lower airspace (<150 m agl) was 78% birds and 22% bats at Hilltop and 70% birds and 30% bats at Mazeppa Ranch during the primary sampling period and 100% birds and 0% bats at Hilltop and 75% birds and 25% bats at Mazeppa Ranch during the secondary sampling period.
Assuming an average of 10 nocturnal h/d, we calculated a turbine passage rate index (number of birds and bats passing within the area occupied by each turbine each night) of 1.9–15.5 nocturnal migrants/turbine/day at Hilltop and 1.8–15.3 at Mazeppa Ranch during the primary sampling period and 1.3–10.7 nocturnal migrants/turbine/day at Hilltop and 2.0–16.5 at Mazeppa Ranch during the secondary sampling period.