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A comparison of breeding population estimators using nest and brood monitoring data.

Baasch DM, Hefley TJ, Cahis SD - Ecol Evol (2015)

Bottom Line: Based on our simulated data, we expect our BPE to be closest to the true number of breeding pairs as compared to other methods.The methods tested resulted in substantially different estimates of the numbers of breeding pairs; however, coefficients from trend analyses were not statistically different.When data from multiple nest and brood surveys are available, the BPE appears to result in reasonably precise estimates of numbers of breeding pairs.

View Article: PubMed Central - PubMed

Affiliation: Headwaters Corporation 4111 4th Avenue Suite 6 Kearney Nebraska 68845.

ABSTRACT
For many species, breeding population size is an important metric for assessing population status. A variety of simple methods are often used to estimate this metric for ground-nesting birds that nest in open habitats (e.g., beaches, riverine sandbars). The error and bias associated with estimates derived using these methods vary in relation to differing monitoring intensities and detection rates. However, these errors and biases are often difficult to obtain, poorly understood, and largely unreported. A method was developed to estimate the number of breeding pairs using counts of nests and broods from monitoring data where multiple surveys were made throughout a single breeding season (breeding pair estimator; BPE). The BPE method was compared to two commonly used estimation methods using simulated data from an individual-based model that allowed for the comparison of biases and accuracy. The BPE method underestimated the number of breeding pairs, but generally performed better than the other two commonly used methods when detection rates were low and monitoring frequency was high. As detection rates and time between surveys increased, the maximum nest and brood count method performs similar to the BPE. The BPE was compared to four commonly used methods to estimate breeding pairs for empirically derived data sets on the Platte River. Based on our simulated data, we expect our BPE to be closest to the true number of breeding pairs as compared to other methods. The methods tested resulted in substantially different estimates of the numbers of breeding pairs; however, coefficients from trend analyses were not statistically different. When data from multiple nest and brood surveys are available, the BPE appears to result in reasonably precise estimates of numbers of breeding pairs. Regardless of the estimation method, investigators are encouraged to acknowledge whether the method employed is likely to over- or underestimate breeding pairs. This study provides a means to recognize the potential biases in breeding pair estimates.

No MeSH data available.


Five estimates of least tern breeding pairs within the central Platte River Valley (top). An evaluation of how each estimate compares to estimates from our breeding pair estimator (BPE; bottom). The comparison in the bottom plot was calculated as (x‐BPE)/BPE, where x is the estimate obtained using one of the four other methods.
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ece31680-fig-0005: Five estimates of least tern breeding pairs within the central Platte River Valley (top). An evaluation of how each estimate compares to estimates from our breeding pair estimator (BPE; bottom). The comparison in the bottom plot was calculated as (x‐BPE)/BPE, where x is the estimate obtained using one of the four other methods.

Mentions: Trends in AHR least tern breeding pair estimates were positively correlated and tended to follow a similar increasing pattern for all nest and brood monitoring methods tested (Table 1; Fig. 5). Regression coefficients for the trend line associated with each method varied from 1.35 (Adult count/2) to 5.55 (cumulative nest counts). The 95% CIs for all trend lines, however, overlapped indicating the regression coefficient for all five methods could be the same (Table 1). As with the simulation experiment, least tern 15 June nest and brood counts provided the lowest estimate of breeding pairs. Maximum nest and brood counts obtained from midmonth (2001–2009) and semimonthly (2010–2014) surveys were highly correlated with BPE (r = 0.96). Cumulative nest counts generally provided the highest annual estimates of breeding pairs. However, it is known that this method would always be biased high unless all breeding pairs only produced a single nest each year.


A comparison of breeding population estimators using nest and brood monitoring data.

Baasch DM, Hefley TJ, Cahis SD - Ecol Evol (2015)

Five estimates of least tern breeding pairs within the central Platte River Valley (top). An evaluation of how each estimate compares to estimates from our breeding pair estimator (BPE; bottom). The comparison in the bottom plot was calculated as (x‐BPE)/BPE, where x is the estimate obtained using one of the four other methods.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4588649&req=5

ece31680-fig-0005: Five estimates of least tern breeding pairs within the central Platte River Valley (top). An evaluation of how each estimate compares to estimates from our breeding pair estimator (BPE; bottom). The comparison in the bottom plot was calculated as (x‐BPE)/BPE, where x is the estimate obtained using one of the four other methods.
Mentions: Trends in AHR least tern breeding pair estimates were positively correlated and tended to follow a similar increasing pattern for all nest and brood monitoring methods tested (Table 1; Fig. 5). Regression coefficients for the trend line associated with each method varied from 1.35 (Adult count/2) to 5.55 (cumulative nest counts). The 95% CIs for all trend lines, however, overlapped indicating the regression coefficient for all five methods could be the same (Table 1). As with the simulation experiment, least tern 15 June nest and brood counts provided the lowest estimate of breeding pairs. Maximum nest and brood counts obtained from midmonth (2001–2009) and semimonthly (2010–2014) surveys were highly correlated with BPE (r = 0.96). Cumulative nest counts generally provided the highest annual estimates of breeding pairs. However, it is known that this method would always be biased high unless all breeding pairs only produced a single nest each year.

Bottom Line: Based on our simulated data, we expect our BPE to be closest to the true number of breeding pairs as compared to other methods.The methods tested resulted in substantially different estimates of the numbers of breeding pairs; however, coefficients from trend analyses were not statistically different.When data from multiple nest and brood surveys are available, the BPE appears to result in reasonably precise estimates of numbers of breeding pairs.

View Article: PubMed Central - PubMed

Affiliation: Headwaters Corporation 4111 4th Avenue Suite 6 Kearney Nebraska 68845.

ABSTRACT
For many species, breeding population size is an important metric for assessing population status. A variety of simple methods are often used to estimate this metric for ground-nesting birds that nest in open habitats (e.g., beaches, riverine sandbars). The error and bias associated with estimates derived using these methods vary in relation to differing monitoring intensities and detection rates. However, these errors and biases are often difficult to obtain, poorly understood, and largely unreported. A method was developed to estimate the number of breeding pairs using counts of nests and broods from monitoring data where multiple surveys were made throughout a single breeding season (breeding pair estimator; BPE). The BPE method was compared to two commonly used estimation methods using simulated data from an individual-based model that allowed for the comparison of biases and accuracy. The BPE method underestimated the number of breeding pairs, but generally performed better than the other two commonly used methods when detection rates were low and monitoring frequency was high. As detection rates and time between surveys increased, the maximum nest and brood count method performs similar to the BPE. The BPE was compared to four commonly used methods to estimate breeding pairs for empirically derived data sets on the Platte River. Based on our simulated data, we expect our BPE to be closest to the true number of breeding pairs as compared to other methods. The methods tested resulted in substantially different estimates of the numbers of breeding pairs; however, coefficients from trend analyses were not statistically different. When data from multiple nest and brood surveys are available, the BPE appears to result in reasonably precise estimates of numbers of breeding pairs. Regardless of the estimation method, investigators are encouraged to acknowledge whether the method employed is likely to over- or underestimate breeding pairs. This study provides a means to recognize the potential biases in breeding pair estimates.

No MeSH data available.