Variables influencing population estimates of an endangered passerine

Morin, Marie P.; Conant, Sheila

doi:10.1016/0006-3207(94)90011-6

Cited by 10 publications

(4 citation statements)

References 21 publications

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“…To estimate F , we assumed that little drift would have occurred in the Laysan population since the translocation, so that allele frequencies from the contemporary Laysan population were used as estimates for generation 0 for each PHR population. Census estimates for the Laysan population from 1968 through to 1988 ranged from ≈ 5000–20 000 finches (Morin & Conant 1994); therefore our assumption seems valid. We used allele frequencies based on the 1986/1987 samples from PHR ( S t = 30, 31, and 27 for Southeast, North, and Grass Islands, respectively), because the exclusion of the 1991 samples for PHR simplified the estimation of t , which was calculated as follows.…”

Section: Methodsmentioning

confidence: 78%

“…To estimate F, we assumed that little drift would have occurred in the Laysan population since the translocation, so that allele frequencies from the contemporary Laysan population were used as estimates for generation 0 for each PHR population. Census estimates for the Laysan population from 1968 through to 1988 ranged from ≈ 5000-20 000 finches (Morin & Conant 1994); therefore Begon & Mortimer 1981) to yield a generation time of 4 years, so t is ≈ 5. Finally, the census estimates available for Laysan between 1968 and 1990 were never below 5000 so we used this as a minimum estimate of N. The reliability of the N e estimate was assessed in two ways.…”

Section: Discussionmentioning

confidence: 99%

“…Alexander Wetmore estimated that 100 finches remained in 1923 when scientists visited Laysan and eradicated the rabbits (Olson 1996). The population recovered rapidly and has fluctuated around a mean of about 10 000 since 1968 (Morin & Conant 1994).…”

Section: Introductionmentioning

confidence: 99%

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Founder events and variation at microsatellite loci in an insular passerine bird, the Laysan finch (Telespiza cantans)

1998

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Historically documented founder events provide opportunities to assess the effects of population size reductions on genetic variation, but the actual magnitude of genetic change can be measured only when direct comparisons can be made to the source or ancestral population. We assayed variation at nine microsatellite loci in the translocated population of the Laysan finch (Telespiza cantans) at Pearl and Hermes reef (PHR), and compared the level of variation to that in the source population on Laysan Island. Heterogeneity in allele frequencies was highly significant at eight of the nine loci, primarily as a result of fluctuations in allele frequencies in the three PHR populations. Intra‐ and interpopulational measures of genetic diversity generally matched predictions based on the well‐documented history of three islet populations at PHR: significantly lower numbers of alleles and polymorphic loci, as well as higher pairwise FST values and genetic distance, were observed for the two populations that underwent severe size reductions. Changes in heterozygosity at single loci were unpredictable, as both significant increases and decreases were observed in founder populations. A significant excess of heterozygotes was found in two populations and was highly significant over all four finch populations (P < 0.003). Estimates of effective population size from temporal changes in heterozygosity and allele frequencies were very small (Ne≤ 30) as a result of the founding events and the constraints of islet area on population numbers. We concluded that the PHR population is not adequate as a secondary genetic reserve for T. cantans, and an alternative refuge needs to be established.

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Section: Methodsmentioning

confidence: 78%

“…To estimate F, we assumed that little drift would have occurred in the Laysan population since the translocation, so that allele frequencies from the contemporary Laysan population were used as estimates for generation 0 for each PHR population. Census estimates for the Laysan population from 1968 through to 1988 ranged from ≈ 5000-20 000 finches (Morin & Conant 1994); therefore Begon & Mortimer 1981) to yield a generation time of 4 years, so t is ≈ 5. Finally, the census estimates available for Laysan between 1968 and 1990 were never below 5000 so we used this as a minimum estimate of N. The reliability of the N e estimate was assessed in two ways.…”

Section: Discussionmentioning

confidence: 99%

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Founder events and variation at microsatellite loci in an insular passerine bird, the Laysan finch (Telespiza cantans)

1998

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“…The use of different observers during each survey period also may have contributed to differences recorded in the bird assemblages between the two survey periods. Several studies have found that estimates of bird abundance can be influenced by observer differences (Kavanagh & Recher 1983; Morin & Conant 1994; Sauer et al . 1994; Cunningham et al .…”

Section: Discussionmentioning

confidence: 99%

Temporal variation in bird assemblages: How representative is a one‐year snapshot?

et al. 2005

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Bird assemblages generally are no longer regarded as stable entities, but rather as fluctuating in response to many factors. Australia's highly variable climate is likely to result in a high degree of dynamism in its bird assemblages, yet few studies have investigated variation on an inter-annual temporal scale. We compared two year-long samples of the bird assemblages of a series of highly fragmented buloke Allocasuarina luehmannii (Casuarinaceae) woodland remnants in south-eastern Australia, the first sample taken in 1994-1995 and the second in [2001][2002]. Bird densities were almost three times higher in the second period than in the first. Mean species richness also was significantly higher. Species richness of each individual site was unrelated between the two years. Minimum species turnover was 63% and was higher, on average, for migratory and nomadic than for sedentary species. Therefore, site-level bird assemblage composition was markedly different between the two survey periods and, on average, the assemblage composition of each site bore greater resemblance to those of other sites in the same year than to that of the same site in the other survey period. Most species changed substantially in their distribution among remnants between the two periods.The change in distribution of most species did not differ significantly from that expected if the species had redistributed at random among the sites. This suggests that although the remnant vegetation of the area is highly fragmented with minimal interpatch connectivity, bird movements among remnants must be relatively frequent. Interannual variability in Australian bird assemblages may be higher than is commonly recognized. In such dynamic systems, we must be cautious when extrapolating from the findings of short-term studies to longer temporal scales, especially in relation to conservation management. A greater understanding of the processes driving Temporal variation in bird assemblages 3 3 distributional patterns is likely to enable better predictions of species' responses to habitat change.

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Personalised ecology and detection functions

Gaston

2020

People and Nature

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1. Direct interactions with nature are important for people's health, well-being and support for pro-nature policies. There is an urgent need better to understand the structure and dynamics of these interactions, and how they differ among individual people, human populations and the communities to which they belong. 2. The determinants of these interactions have two components. First are the factors that influence whether someone undertakes actions that may lead to interactions with nature (e.g. looking through a window, going for a walk, travelling to the countryside). These factors have attracted significant attention. Second are the factors that influence what nature interactions are obtained when someone is present in a situation in which these could occur. These have received little explicit attention. 3. One way of formalizing understanding, and identifying gaps in knowledge, of the second group of factors is to consider human-nature interactions in terms of detection functions. Rather than using such functions for the estimation of species abundances, the purpose for which they were originally developed, they can be reorganized as descriptors of influences on people's nature interactions. 4. This paper considers how the different variables contained within detection functions influence human-nature interactions, and in particular how the number of nature interactions a person has in a given place and time is shaped both by clearly 'nature'-associated variables, such as the number of organisms present, and also by variables that are strongly influenced by characteristics of the observer, such as how they use or explore an area and their personal nature detection abilities. 5. Many issues explored in the context of human-nature interactions are then seen to concern these component variables of detection functions, and approaches to improving the frequency of interactions seen, in effect, to be targeted at affecting change in different ones of these variables.

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Variables influencing population estimates of an endangered passerine

Cited by 10 publications

References 21 publications

Founder events and variation at microsatellite loci in an insular passerine bird, the Laysan finch (Telespiza cantans)

Founder events and variation at microsatellite loci in an insular passerine bird, the Laysan finch (Telespiza cantans)

Temporal variation in bird assemblages: How representative is a one‐year snapshot?

Personalised ecology and detection functions

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