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Density-dependent reproductive output in relation to a drastically varying food supply: getting the density measure right

Lindström, Åke LU ; Enemar, A; Andersson, G; von Proschwitz, T and Nyholm, NEI (2005) In Oikos 110(1). p.155-163
Abstract
When a limiting resource (e.g. food) varies drastically between years, and population density is measured in the conventional way as individuals per area, demographic processes such as productivity and survival may erroneously be considered density-independent. We tested the hypothesis that if the variation in a limiting resource is not taken into account in the density measure, this may lead to erroneous conclusions about the density-dependence of demographic variables. We studied the food-related variation in productivity of bramblings Fringilla montifringilla, an insectivorous passerine bird, using 19 years of standardised insect censusing, bird censusing and mist-netting of birds in subalpine birch forest in Swedish Lapland. The yearly... (More)
When a limiting resource (e.g. food) varies drastically between years, and population density is measured in the conventional way as individuals per area, demographic processes such as productivity and survival may erroneously be considered density-independent. We tested the hypothesis that if the variation in a limiting resource is not taken into account in the density measure, this may lead to erroneous conclusions about the density-dependence of demographic variables. We studied the food-related variation in productivity of bramblings Fringilla montifringilla, an insectivorous passerine bird, using 19 years of standardised insect censusing, bird censusing and mist-netting of birds in subalpine birch forest in Swedish Lapland. The yearly variation in our measure of brambling per capita productivity (numbers of juveniles per adult trapped) was explained to 30-40% by the larvae abundance of the moth Epirrita autumnata. Taking larvae density into account, no other environmental variable (inferred predation pressure, breeding phenology, and summer temperature) was significantly related to variation in reproductive output. There was no effect of brambling population density on per capita productivity, that is, when density was measured the conventional way, productivity seemed density-independent. However, per capita productivity was significantly and negatively correlated to the food-related population density (population density divided by larval density), supporting the hypothesis that not including a limiting resource into the density measure may indeed lead to erroneous conclusions about the density-dependence of demographic variables. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Oikos
volume
110
issue
1
pages
155 - 163
publisher
Wiley-Blackwell
external identifiers
  • wos:000229069700015
  • scopus:20444365536
ISSN
1600-0706
DOI
10.1111/j.0030-1299.2005.13828.x
language
English
LU publication?
yes
id
4b27d9de-3a59-45ad-b809-ef555106e1bf (old id 145311)
date added to LUP
2007-06-25 14:56:20
date last changed
2017-11-12 03:23:35
@article{4b27d9de-3a59-45ad-b809-ef555106e1bf,
  abstract     = {When a limiting resource (e.g. food) varies drastically between years, and population density is measured in the conventional way as individuals per area, demographic processes such as productivity and survival may erroneously be considered density-independent. We tested the hypothesis that if the variation in a limiting resource is not taken into account in the density measure, this may lead to erroneous conclusions about the density-dependence of demographic variables. We studied the food-related variation in productivity of bramblings Fringilla montifringilla, an insectivorous passerine bird, using 19 years of standardised insect censusing, bird censusing and mist-netting of birds in subalpine birch forest in Swedish Lapland. The yearly variation in our measure of brambling per capita productivity (numbers of juveniles per adult trapped) was explained to 30-40% by the larvae abundance of the moth Epirrita autumnata. Taking larvae density into account, no other environmental variable (inferred predation pressure, breeding phenology, and summer temperature) was significantly related to variation in reproductive output. There was no effect of brambling population density on per capita productivity, that is, when density was measured the conventional way, productivity seemed density-independent. However, per capita productivity was significantly and negatively correlated to the food-related population density (population density divided by larval density), supporting the hypothesis that not including a limiting resource into the density measure may indeed lead to erroneous conclusions about the density-dependence of demographic variables.},
  author       = {Lindström, Åke and Enemar, A and Andersson, G and von Proschwitz, T and Nyholm, NEI},
  issn         = {1600-0706},
  language     = {eng},
  number       = {1},
  pages        = {155--163},
  publisher    = {Wiley-Blackwell},
  series       = {Oikos},
  title        = {Density-dependent reproductive output in relation to a drastically varying food supply: getting the density measure right},
  url          = {http://dx.doi.org/10.1111/j.0030-1299.2005.13828.x},
  volume       = {110},
  year         = {2005},
}