Power to detect trends in abundance of secretive marsh birds: Effects of species traits and sampling effort

Robert J Steidl, Courtney J. Conway, Andrea R. Litt

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Standardized protocols for surveying secretive marsh birds have been implemented across North America, but the efficacy of surveys to detect population trends has not been evaluated. We used survey data collected from populations of marsh birds across North America and simulations to explore how characteristics of bird populations (proportion of survey stations occupied, abundance at occupied stations, and detection probability) and aspects of sampling effort (numbers of survey routes, stations/route, and surveys/station/year) affect statistical power to detect trends in abundance of marsh bird populations. In general, the proportion of survey stations along a route occupied by a species had a greater relative effect on power to detect trends than did the number of birds detected per survey at occupied stations. Uncertainty introduced by imperfect detection during surveys reduced power to detect trends considerably, but across the range of detection probabilities for most species of marsh birds, variation in detection probability had only a minor influence on power. For species that occupy a relatively high proportion of survey stations (0.20), have relatively high abundances at occupied stations (2.0 birds/station), and have high detection probability (0.50), ≥40 routes with 10 survey stations per route surveyed 3 times per year would provide an 80% chance of detecting a 3% annual decrease in abundance after 20 years of surveys. Under the same assumptions but for species that are less common, ≥100 routes would be needed to achieve the same power. Our results can help inform the design of programs to monitor trends in abundance of marsh bird populations, especially with regards to the amount of sampling effort necessary to meet programmatic goals.

Original languageEnglish (US)
Pages (from-to)445-453
Number of pages9
JournalJournal of Wildlife Management
Volume77
Issue number3
DOIs
StatePublished - Apr 2013

Fingerprint

marshes
marsh
bird
birds
sampling
effect
trend
station
surveying
uncertainty
detection
monitoring

Keywords

  • marsh birds
  • monitoring
  • power analysis
  • rails
  • trends
  • wetland birds
  • zero-inflated Poisson

ASJC Scopus subject areas

  • Nature and Landscape Conservation
  • Ecology
  • Ecology, Evolution, Behavior and Systematics

Cite this

Power to detect trends in abundance of secretive marsh birds : Effects of species traits and sampling effort. / Steidl, Robert J; Conway, Courtney J.; Litt, Andrea R.

In: Journal of Wildlife Management, Vol. 77, No. 3, 04.2013, p. 445-453.

Research output: Contribution to journalArticle

@article{cfa862357e3d4c2a97cede7d62519e56,
title = "Power to detect trends in abundance of secretive marsh birds: Effects of species traits and sampling effort",
abstract = "Standardized protocols for surveying secretive marsh birds have been implemented across North America, but the efficacy of surveys to detect population trends has not been evaluated. We used survey data collected from populations of marsh birds across North America and simulations to explore how characteristics of bird populations (proportion of survey stations occupied, abundance at occupied stations, and detection probability) and aspects of sampling effort (numbers of survey routes, stations/route, and surveys/station/year) affect statistical power to detect trends in abundance of marsh bird populations. In general, the proportion of survey stations along a route occupied by a species had a greater relative effect on power to detect trends than did the number of birds detected per survey at occupied stations. Uncertainty introduced by imperfect detection during surveys reduced power to detect trends considerably, but across the range of detection probabilities for most species of marsh birds, variation in detection probability had only a minor influence on power. For species that occupy a relatively high proportion of survey stations (0.20), have relatively high abundances at occupied stations (2.0 birds/station), and have high detection probability (0.50), ≥40 routes with 10 survey stations per route surveyed 3 times per year would provide an 80{\%} chance of detecting a 3{\%} annual decrease in abundance after 20 years of surveys. Under the same assumptions but for species that are less common, ≥100 routes would be needed to achieve the same power. Our results can help inform the design of programs to monitor trends in abundance of marsh bird populations, especially with regards to the amount of sampling effort necessary to meet programmatic goals.",
keywords = "marsh birds, monitoring, power analysis, rails, trends, wetland birds, zero-inflated Poisson",
author = "Steidl, {Robert J} and Conway, {Courtney J.} and Litt, {Andrea R.}",
year = "2013",
month = "4",
doi = "10.1002/jwmg.505",
language = "English (US)",
volume = "77",
pages = "445--453",
journal = "Journal of Wildlife Management",
issn = "0022-541X",
publisher = "Wiley-Blackwell",
number = "3",

}

TY - JOUR

T1 - Power to detect trends in abundance of secretive marsh birds

T2 - Effects of species traits and sampling effort

AU - Steidl, Robert J

AU - Conway, Courtney J.

AU - Litt, Andrea R.

PY - 2013/4

Y1 - 2013/4

N2 - Standardized protocols for surveying secretive marsh birds have been implemented across North America, but the efficacy of surveys to detect population trends has not been evaluated. We used survey data collected from populations of marsh birds across North America and simulations to explore how characteristics of bird populations (proportion of survey stations occupied, abundance at occupied stations, and detection probability) and aspects of sampling effort (numbers of survey routes, stations/route, and surveys/station/year) affect statistical power to detect trends in abundance of marsh bird populations. In general, the proportion of survey stations along a route occupied by a species had a greater relative effect on power to detect trends than did the number of birds detected per survey at occupied stations. Uncertainty introduced by imperfect detection during surveys reduced power to detect trends considerably, but across the range of detection probabilities for most species of marsh birds, variation in detection probability had only a minor influence on power. For species that occupy a relatively high proportion of survey stations (0.20), have relatively high abundances at occupied stations (2.0 birds/station), and have high detection probability (0.50), ≥40 routes with 10 survey stations per route surveyed 3 times per year would provide an 80% chance of detecting a 3% annual decrease in abundance after 20 years of surveys. Under the same assumptions but for species that are less common, ≥100 routes would be needed to achieve the same power. Our results can help inform the design of programs to monitor trends in abundance of marsh bird populations, especially with regards to the amount of sampling effort necessary to meet programmatic goals.

AB - Standardized protocols for surveying secretive marsh birds have been implemented across North America, but the efficacy of surveys to detect population trends has not been evaluated. We used survey data collected from populations of marsh birds across North America and simulations to explore how characteristics of bird populations (proportion of survey stations occupied, abundance at occupied stations, and detection probability) and aspects of sampling effort (numbers of survey routes, stations/route, and surveys/station/year) affect statistical power to detect trends in abundance of marsh bird populations. In general, the proportion of survey stations along a route occupied by a species had a greater relative effect on power to detect trends than did the number of birds detected per survey at occupied stations. Uncertainty introduced by imperfect detection during surveys reduced power to detect trends considerably, but across the range of detection probabilities for most species of marsh birds, variation in detection probability had only a minor influence on power. For species that occupy a relatively high proportion of survey stations (0.20), have relatively high abundances at occupied stations (2.0 birds/station), and have high detection probability (0.50), ≥40 routes with 10 survey stations per route surveyed 3 times per year would provide an 80% chance of detecting a 3% annual decrease in abundance after 20 years of surveys. Under the same assumptions but for species that are less common, ≥100 routes would be needed to achieve the same power. Our results can help inform the design of programs to monitor trends in abundance of marsh bird populations, especially with regards to the amount of sampling effort necessary to meet programmatic goals.

KW - marsh birds

KW - monitoring

KW - power analysis

KW - rails

KW - trends

KW - wetland birds

KW - zero-inflated Poisson

UR - http://www.scopus.com/inward/record.url?scp=84875722871&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84875722871&partnerID=8YFLogxK

U2 - 10.1002/jwmg.505

DO - 10.1002/jwmg.505

M3 - Article

AN - SCOPUS:84875722871

VL - 77

SP - 445

EP - 453

JO - Journal of Wildlife Management

JF - Journal of Wildlife Management

SN - 0022-541X

IS - 3

ER -